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CPRI-Training Notes
1
Growth Of Powersector And Industry in India
By G Venkatraman,Consultant-Cpri
1.0 Evolution Of Indian Power Sector
• Pre-Independence- Power Was Available In Small Pockets Of India;
• This Was More Visible In ‗Princely States‘ Owned By Maharajas;
• British Rulers Provided ‗Power Source‘ In National Capital And Selected
Cities With Commercial Interest;
• Olliery Areas Were Provided With ‗Steam‘ Power Units;
• Other Sources Were ‗Dg‘ Units With Limited Ditribution Capability;
• Some Of The Big Industry E.G. Tata Steel Co. Jamshedpur Had Large Captive
Plant (60mw);
• All Generators Were From ‗Great Britain‘
2.0 Capacity And Energy- Comparison
• Installed Capacity In 1950- 1362 Mw
• Gross Energy Generation -4073 Mu
• Per Capita Consumption- 16.3 Units;
• Installed Capacity In 31/3/2011 – 182689mw;
• Gross Energy Generation 2010-11 – 789,013mu
• Per Capita Consumption In 2010-11 813.5mu;
3.0 Existing Power System
• Indiawas Declared A Sovereign Republic In 1950;
• There Were Number Of ‗Princely‘ Estates In 1955-60 Period Having Power
Generation For Palace.
• The First Maharaja To ‗Join‘ The Republic Of India Was ‗Maharaja Of
Mysore‘. He Donated His Asset Including Power Supply System For
Development Purpose.
• All The Other Maharajas Followed On Same Line.
• The Existing Power Generation And Supply Network Was Extended To More
Areas;
• Karnataka(Formerly Mysore) Was Getting Power From ‗Hydro‘ Generation
Plants -‗Sharavati, ‗Jog‘ And ‗Linganmakki‘ Reservoirs;
4.0 Administrative Arrangement (Central Electricity Authority)
• The Central Electricity Authority Of India (Cea) Is A Statutory
Organisation Constituted Under Section 3(1) Of Electricity Supply Act
1948, Subsequently Superseded By Section 70(1) Of The Electricity Act
2003.
• Cea Has Provided Advisory And Supervisory Support To Government
On Matters Relating To
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National Electricity Policy
Formulates Short-Term And Long Term Perspective Plans For
The Development Of Electricity System.
Assessmentof Power Demandfor Concurrentnational 5 Yearplan;
5.0 National „5 Year Perspective Plan‟
Growth Of Power Generation Capacity
Plan Period Installed Capacity(Mw) At End Of Plan
Hydroonly Total % Of Hydro In Total
1st Plan(1950-56) 1061 2886 36.75
2nd
Plan(1956-61) 1917 4653 41.19
3rd
Plan (1961-66) 4124 9027 45.68
4th
Plan (1966-74) 6966 16664 41.8
5th
Plan (1974-79) 10833 26680 40.6
6th
Plan (1979-85) 14460 42565 3.96
7th
Plan (1985-90) 18307 63636 28.77
8th
Plan (1990-97) 21658 85795 25.24
9th
Plan (1997-02) 26269 105046 25.00
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6.0 Hydro‟ Plants–First Power Source
Some Of The Major Hydro Plants Which Were Established During 1955 And
1980 Period Are-
1. Bhakra-Nangal Project (Multi Purpose);
2. Rihand (Pipri) Project;
3. Obra Hydro Project;
4. Damodar Valley Project;
5. Bhadra Reservoir Project;
6. Hirakud And Rengali Dam Project;
7. Upper And Lower Silleru Hydro Project;
8. Koyna Project;
9. Nagarjunasagar Hydro Project;
There Are Many Other Projects In ‗Nort-East‘ And Other States, Not Listed Here.
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7.0 Adoption Of British Practice
• Indian Power System Adopted The Former ‗British‘ Standards I.E.
Power System Voltage Were Graded Into Levels Of 110kv, 66kv, 22kv, 6.6 Kv,
3.3 Kv And 3phase ‗Lt‘ System Was 415 & 230v (1ph).
Power System Frequency - 50hz;
• Machines And Equipment Of Earstwhile ‗British‘ Manufacturing Companies In
India Were Available With Indegenous Cpability.
• Gec, Biecco-Lawrie, Reyrolle-Burn Were Established Electrical Equipment
Manufacturers;
• National Level Industry Such As ‗Ngef‘, Bhel Were Established;
8.0 Formation Of „State Electricity Board
Prior To Formation Of Provinces/State On ‗Linguistic‘ Basis, The Administaration System
Was In The Form Of ‗Electricity/Power Department‘
i) On Formation Of Provinces/State‗State, ‗State Elctricity Board‘ Were
Constituted By Respective State Government;
ii) ‗Electricity‘ Was Deemed As Concuurent Subject Of ‗Centre‘ And ‗State‘.
This Enabled Respective States To Plan The Development Of All
iii) The Three Desciplines Of Power System I.E. Generation, Transmission And
Distribution Under ‗Singular‘ Administrative Board;
9.0 Demand Forecast Andconsumption
i) Electricty Being A ‗Non‘ Storable Commodity, The Production And
Consumption Is Simultaneous;
ii) Economy Of A Country Is Directly Dependent On Availability Of This
Commodity At Reasonable Cost And Quality; Per Capita Consumption Is
Another Index Of Propseprity Of The Country.
iii) The Two Parameters To Assess The Availability Of This Commodity Are ‗Load
Or Power‘ (In Watts) And ‗Energy‘ (Watt X Hour) ;
Both Are Interlinked But Need Separate Resource Provision;
‗Load Or Power Demand‘ Is Linked To System/Equipment Capacity At An
Instant;
‗Energy‘ Supply Is Linked To Serving All Consumers For The Total
‗Duration‘ (Hour, Month And Year);
10.0 National Power Survey‟ By Cea
The Main Objective Of This Survey And Prepare A Repot Is To:
1. Forecast Year Wise Electricity Demand For Each ‗State‘, Union Teritory,
Region And All India, In Detail Upto End Of The Next 5 Year Plan Period;
2. To Project Perspective ‗Electricity‘ Demand For The Terminal Years Of Two
Subsequent 5 Year Plan Durations;
3. The Demand Analysis And Forecast Would Thus Cover 15year Period.
(Example: 14th
‗Eps‘ Was For Year Wise Forecastin 11th
5 Year Plan Period
(2007-2012) And Total Electricity Demand Projection Upto End Of 2021-22).
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4. Model Used Is Called As ‗Partial End Use Method‘ (Peum);
- For The Assessment Of Load Demand, Capacity Addition Of Generator,
Transformer And Distribution Sub Stations Ineach State, Power Survey
Was Conducted By ‗Cea‘.
- Load Demand Input And Proposal For Establishing Power Stations In
Each State To Meet The Load, Provided By Each State;
Main 5 Heads In The Demand Group:
1. Domestic Consumer;
2. Public Lighting & Public Water Works;
3. Commercial & Misc. Consumers;
4. Irrigation Pumpset;
5. Indutrial (Ht & Lt) Load;
6. Railways Traction And Non-Industrial ;
10.0 Generation And Transmission Planning
Growth Of Installed Capacity Vs Generation
End Of Year Installed. Cap (Mw) End Of Year Installed. Cap (Mw)
1947 1362 1980 30283
1950 1713 1985 42710
1956 2813 1990 64112
1961 5063 1992 69915
1966 9583 1997 86337
1969 13703 2002 105456
1974 18282 2007 132329
1979 28484 2011 182689
Energy Produced Vs Per Capita Consumed
End Of Year (Mu)
Generation Per Capita Consumption
1950 5106 18.2
1956 9662 30.9
1961 16937 45.9
1966 32990 73.9
1969 47434 97.9
1974 66689 126.4
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1979 102523 171.6
1980 104627 172.4
1985 156859 228.7
1990 245438 329.2
1992 287029 347.5
1997 395889 46436
2002 517439 599.2
2007 624495 671.9
2011 789013 813.5
Growth Of 400 Kv „Ehv‟ System From Year 1978 Onwards
End Of Year
Growth Of Transmission System (Length In Kms.)
220 Kv 400 Kv 765kv Hvdc
'Bi Pole’ Total
2006 114629 75722 1704 5872 197927
During 2007-11 19561 26856 1636 1580 49633
Mar‘
2011 140757 114979 4164 9452 269352
11.0 Poor Health Of Power Sector
Some Reasons For Poor Health Of Indian Power System:
1. Exponential Demand Growth-Beyond Forecast
2. High Capital And Running Cost ;
3. Low Recovery Of Investment;
4. Fund Constraint In State And Centre;
5. High ‗T & D‘ Loss;
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6. Theft Of Power In Many States;
Solutions Proposed By Consultants And Committes
Implement ‗Power Reform‘–Administrative & Technical
Modify I.E. Act- ;
Introduce Regulatory Regime In Phases;
Invite Private Power Producer;
Appoint Electricity Regulator As ‗Neutral‘ Empire;
Unbundelling Of ‗Sebs‘ Into Separate Utilities;
Central Support In Rural And Urban Ditribution-Rggvy& Rapdrp Schemes;
12.0 Administrative Reform
Formation Of Central & State Level Regulatory Commissions.
13.0 Technical Reforms
1. Specification Of Equipment ‗Up-Graded‘ And Guideline Documents Prepared
By ‗Cea‘.
2. It Based System In Distribution Area;
3. Use Of ‗Scada‘ In Transmission System;
4. Introduction Of ‗Smart Grid‘ Concept In Entire Poewer Sector;
5. Use Of ‗Smart Meters‘ And Pre-Paid Meter System By Utilities;
6. Installation Of ‗Uhv‘ And ‗Ehv‘ Transmission System And Integration Of 4
Regions In Synchronous Mode;
7. ‗Abt‘ Metering System Usage For Better ‗Grid‘ Discipline;
8. Integration Of Renewable Energy (Wind,Solar Etc.) Into Grid;
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Electricity Distribution in India, private participation in Distribution reforms
P.ChandhraSekhar, CPRI, Distribution Systems Division, Bangalore
1.Introduction- Distribution
The overall quantity of electricity expended per head in the country was 600 kWh. The industrial
sector accounted for about 35.6% of the total expenditure. The domestic segment used up
around 24.8% of the electricity. Consumption by the commercial and the agricultural sector
stood at 8.1% and 22.9% individually. The normal per capita consumption came to about 600
KWH.Along with economic growth and a reduction in the below the poverty level populace, the
per capita electricity spending is sure to rise. Therefore, in order to support a rate of growth
of GDP of around 7 percent per annum, the rate of growth of power supply needs to be over
10 percent annually. The govt. enunciated policy in 1991, allowing private enterprise a larger
role in the power sector.
In the last few years, the focus of the debate and action on power sector reforms
has shifted from generation to distribution side.Several committees, policy documents, and
reform plans have espoused the need for privatization of distribution and have suggested
several actions in terms of legislative and regulatory changes to make privatization of
distribution successful.
The Electricity Act 2003 (EA 2003) is a major step forward to improve and speed up
the power sector reforms in India. Post EA 2003 the power industry has opened up in
generation, transmission, and distribution sector. The opportunities are as follows.
1 .1 Opportunities
The opportunities in the Power Industry in India during Post EA 2003 as follows:
1.1.1 DE licensing of Generation Project
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Generation projects de-licensed subject to meeting the criteria laid out in National
Policy
No TEC clearance required for any thermal generation projects and for hydel upto
500 MWCaptive plant freed from licensing
1.1.2 Open Access
Distribution along with Generation gives lot of opportunities for investors having
CPP to use the open access transmission system
Different entities with varying business models will emerge and will be prospective
participants in the market
Surcharge for meeting the cross subsidy will not be livable in case of open access,
ifProvided to a person who has established CPP for carrying electricity to the
destination of his own use
1.1.3 Multiple Licenses
Multiple licensees allowed distributing electricity within the same distribution circle
Distribution licensee does not require a separate trading license
A consumer could source power from any person other than the Licensee of that
area on payment of additional surcharge
No license is required for generation as well as distribution in forward rural areas
1.1.4 Distributed Generation
The Act gives a freedom to set up own Captive Power Plant and Distribute Electricity
in rural areas as notified by the Govt. without license. This gives huge investment
opportunities to small entrepreneurs for setting up generating plants and distributes
electricity as a lot of risks are mitigated. The excess power can be sold to third party.Rural
Energy Systems will emerge, enabling entities like Users Associations / Co-operatives to also
support trading at local levels.
1.1.5 Antitheft Legislation
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The provision for antitheft legislation will help in reducing the commercial losses of
the utilities and gives a boost to possible investors who were earlier hesitant to invest in this
sector.
1.1.6 Franchisee
A distribution licensee can distribute electricity through another person within its
distribution area. This will make way for micro distribution system concept through
franchisees.
1.1.7 Market Challenges Competition& Risks
The market challenges in terms of competition and risks involved in the Power
Industry for BESCOM in the Post EA 2003 scenario are explained below in table 1.1 and table
1.2.
1.1.7.1 Competition
Table 1.1:Product Differentiation-Competition
Major Competitor Product/
services
PRODUCT DIFFERENTTIATION
BESCOM Competitors
Captive Generation by High value consumers
Electricity Grid support and multiple power sourcing avenues.
Lesser reliability and concerns of stranded /suboptimal investment. Promotes the concept in
industrial circles of “Leaving the non-core
activities”
No / Low entry
barriers (Sec 9 of
EA 2003). Low cost without cross subsidy component in tariff(no surcharge of wheeling)
No universal service
obligation
Retail competition -
Switchover of our
Consumers By way
of open access
Electricity Efficient consumer
service, Higher network
reliability & regulated tariff
to protect revenue
leakage through levy of
wheeling charges,
surcharge etc
Low cost and
possibility of offering
bundled services,
better branding
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Retail competition -
Switchover of our
Consumers - By
Parallel Network
Electricity Lower cost due to
depreciated asset & high
switchover cost to
consumer in terms of
additional surcharge
Higher reliability and
efficient system
parameters like
voltage etc
1.1.7.2 Risks
Major risks with their impact and action plan for mitigation of those risks are shown in
tabular form below:
Table 1.2:Product Differentiation-Risks
Major Risks Impact ( Nature and Time of Incidence )
Operational
Performance Risk
T& D loss estimation Methodology
Non achievement of targeted AT & C loss reduction levels
Delay in completion of identified projects & augmentation works
Regulatory Risk in
terms of Tariff setting
Lower Rate of Return (lower or non-admissibility of a particular costcomponent in the Annual Revenue Requirement (ARR) – an exercise undertaken annual)
Availability of cash for Appropriation of Dividend after providing for deferred tax & Depreciation
Financial Risks Funding for Capex scheme
Loan Repayments after 5 years
Transitional Support - inadequacy of Govt. Subsidy – may put pressureon assured 16% RoEExtent of Revenue gap
Govt. Support RoW permissionLandLaw & Order situation
Transmission &
Supply Risks
Shortfall in Quantity of electricity required for the licensed areaHigher price for incremental power
Others – UI, Reactive charges etc
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Market Risks Decrease in overall revenue due to competition in retail supply and/or increased Captive Generation by high value consumers
Inadequate cost recovery including reasonable return due to decreased sales volume because of adverse consumer mix and/or some
Buyers shifting to other Retailer/ Licensee as and when open access is introduced in distribution segment
Quality of Manpower Sub- optimal cost centers
Senior Management Capability
Risks arising out of
mis-interpretation/gaps in
Transfer scheme
Unfunded liability arising out of VRS in Pension Trust
Exhaustion of Transitional Support - inadequacy of Govt. Subsidy Land & RoW requirement
2. Distribution Performance Parameters
The functional areas for performance parameters are proposed as follows:
2.1Operational Performance:The availability, reliability, and quality of power
Delivered to consumers, provision of maintenance and repair services, and level of
Technical and commercial losses.
2.2Customer Service: Provision of key customer services such as connection
Services, handling of complaints, consumer education activities, testing services,
DSM programs.
2.3.Metering, Billing and Collection: Extent and accuracy of metering, billing
Practices, collection efficiency, arrears on receivables.
2.4.Financial Performance and Competitiveness: Cost recovery, profitability, level
of capital investment (and reinvestment), and comparative tariff levels.
2.5.Operational Cost Control:Total cost of distribution services, staffing levels and
labor costs, other operating and capital costs, inventory management.
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The following parameters will be evaluated in the Distribution Business as shown in Table 1.3 .
Table 1.3: Performance of parameters
Area Performance Measure Effect Measured Data Source
Op
erat
ion
al P
erfo
rman
ce
SAIFI Frequency of outages Sub Station Logs
SAIDI Duration of outages Sub Station Logs
CAIDI Duration-Frequency Sub Station Logs
Aggregate technical &
commercial losses
Effectiveness in
minimizing
unrecoverable energy
cost
Reports to regulators
or internal
Technical losses Efficiency of
distribution
infrastructure
Substation energy
audits/load flow
studies
Unplanned outages/total
outages
Relative impact of
outages
on customers and
system
Substation reports
Service restoration time
distribution
Responsiveness of
maintenance
Substation, district
serv.
logs
Annual replacement rate of
distribution transformers
(%)
Role of transformer
failures
in maintenance effort
Maintenance and
equipment records
Area Performance Measure Effect Measured Data Source
Cust
om
er
Ser
vic
e
Lead time for new
connections
Responsiveness and
service
orientation of
connection
services
Customer account
records
Lead time to test/replace
meters in case of complaint
Commitment to
metering
accuracy
Customer account and
meter service records
Response time from fault
complaint to service visit
Effectiveness of
complaint
response
Customer account and
service records
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Customer care personnel
per customer
Adequacy of customer
service resources
Employment records
Employees providing
special services per 1000
customers
Provision of value-
added
services to customers
Employment and
special program
records
Area Performance Measure Effect Measured Data Source
Met
erin
g,
Bil
lin
g a
nd
Co
llec
tio
n
Metered customers/total
customers
Ability to bill
consumers for
energy consumption
Aggregated reports or
customer account
records
Meters/meter reader Adequacy of resources Employee records
Frequency of meter/seal
inspection
Control of tampering
and
maintenance of
accuracy
Service and customer
account records
Meters replaced/meters in
service
Adequacy of meter
technology
Service records
% of bills that are
estimated
Billing accuracy Meter reading/billing
policy
Time lag between meter
reading and bill dispatch
Billing efficiency Billing reports and
records
Ave level of customer
arrears
Collection efficiency Accounting records
Area Performance Measure Effect Measured Data Source
Co
st a
nd
Man
agem
ent Distribution cost/unit Operating efficiency
and cost
reasonableness
Financial reports
Functional shares of non-
energy
distribution costs:
admin, maintenance,
equipment, etc.
Norms of cost
allocation
Cost accounting
reports
Total labor cost/customer Labor cost efficiency Financial reports
Employees/customer Employment level
norm
Employment records
Training participant
days/employee-year
Adequacy of training Human
resource/training
records
Sick and injury
days/employee
Safety practices Human resource
records
Area Performance Measure Effect Measured Data Source
Fin
anci
al
Per
form
anc
e
Average tariff levels by class Competitiveness Tariff sheets, internal
reports
Cost recovery (op
revenue/cost)
Sustainability of cost
levels/ tariffs
Financial reports
Ave capital exp/net asset
value
Capital sustainability Financial reports
Customer
receivables/monthly
revenue collections
Cash flow
management
Internal accounting
reports
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Commercial losses (% of
sales)
Control of theft and
unaccounted losses
Reports on AT&C
losses and estimates
of
technical losses
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3. Distribution Business Models:
The Distribution franchise model is a public private Partnership Initiative (PPP) that has emerged as a solution to the problems affecting the Power Distribution business –high technical and commercial losses, Poor Infrastructure, weak financial position and lack of customer orientation. The model as evolved as a means to break the vicious cycle of low realisation, low investments, low consumer satisfaction and in turn low realisation. The first input and investment based distribution franchise model has been implemented in the bhiwandi circle in Maharastra with exemplary success.
3.1 Challenges:
Despite Bhiwandi’s exemplary success ,the progress in distribution franchising is very slow.The following are the two major factors that are hampering the progress and the solutions that can be implemented to overcome the challenges.
3.1.1 Inadequate Power Supply:
Although the distribution franchise model aims to cut distribution losses and improve customer service, the franchisee dependent on the utility of electricity supply.The licensee usually guarantees usually to provide the same volume of energy that was supplied in the previous year, thud lending an element of certainty to the franchisee’s business model.
Most states in India face electricity shortages .Despite the guaranteed quantum of electricity supply, there are shortfalls and the distribution franchisees have to resort to loading .Thus the objective of improvement in customer service is only partially achieved.
Going forward, a key driver will be the ability of the distribution franchisee to bring in additional power supply. A model under which the franchisee required to achieve 100 percent supply levels ( By sourcing additional power ) in the medium term (Two to three years) will find favour with the franchising utility as well as the consumers. Thus it can be a preferred model and provide impetus to distribution franchising .
This revised model would open up new opportunities for players that are backward integrated into generation and /or have the ability to source additional power.The power generated /sourced by them will find a captive market and thus de risk the business models in the long run.
3.1.2 Rehabilitation of the existing employees of the Utility
Another major impediment is rehabilitation of the licensees existing employees in the area to be franchised. While the franchise model in the current form addresses the concerns of the consumers, the licenses and the franchisee .the concerns of the existing employees are not addressed effectively. Since it is not obligatory for the franchisee to take on the existing employees of the utility. Most of the staff has to be transferred to the other distribution areas under the utility.
The utility and the franchisee need to work together to ensure that the majority of the existing employees can be absorbed in the same area through training and reskilling. Further the utility
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should work out a compassionate transfer process for the employees who are to be transferred to other areas. This will ensure acceptance amongst the utilitys employees and smooth transition.
4. Concept of AT&C loss& its impact on Business :
The following are the different losses evaluated in the distribution system
4.1 Technical losses: Every element in a power system- a line- a transformer etc. consumes some energy because of its inherent property while performing their expected duty. Cumulative energy by all these elements constitutes technical losses i.e I2R losses. These losses cannot be avoided completely from the system but may be reduced as far as possible by improving the ST&D system. Some of the major reasons for the technical losses to occur in the system are mentioned below
• Lengthy Distribution (11 KV & LT) lines
11 KV & LT lines are extended for unduly long distances in Rural Areas (low load density)
• Inadequate Conductor sizes
Initially lower size conductors not replaced with load growth. • Haphazard and adhoc planning ignoring scientific methods • Wrong location of DTRs with incorrect ratings • Low power factors – no control over reactive power • Low voltage pockets • Bad workmanship
4.2 Commercial losses: These losses occur on account of following
Non performing meters
Under performing meters
Meters not read
Application of lower multiplication factors
Pilferage by manipulation
Theft by direct tapping etc.
Here it is to mention that many distribution companies across the country are adopting the approach of “100% consumer metering and Total Energy Audit” to curb thecommercial loss. While load flow analysis is universally used for technical loss estimation, the commercial loss is obtained by subtracting technical loss from the total loss .
AT&C losses:
=(1- billing Efficiency x collection efficiency ) * 100
= Billing Efficiency:Energy Billed
Input Energy ∗ 100
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= Collection Efficiency: Revenue Collected
Amount Billed ∗ 100
High technical losses in the system are primarily due to inadequate investments over the years for system improvement works, which has resulted in unplanned extensions of the distribution lines, overloading of the system elements like transformers and conductors, and lack of adequate reactive power support.
The commercial losses are mainly due to low metering efficiency, theft & pilferages. This may be eliminated by improving metering efficiency, proper energy accounting & auditing and improved billing & collection efficiency. Fixing of accountability of the personnel / feeder managers may help considerably in reduction of AT&C loss.
It reduces the customer satisfaction level and poor investment in the distribution business .The utility will not be financially viable and Average Revenue Realisation will come down. The Average cost of supply will be increased. The overall brand image of the company will decrease.
5. References
1. Performance benchmarks for electricity distribution business in south asia(2004), Nexant
2. Technology: Enabling the transformation of Power Distribution, Infosys Report (2008)
3. Distribution Franchise, Evolution, Experience and outlook, Power line (2009)
4. www.Powermin.nic.in
Maintenance and diagnostic testing of Distribution Transformers By K.Mallikarjunappa, Joint Director,Central Power Research Institute, Bangalore
Introduction
Distribution Transformers form the largest population of transformers in the Electrical Power Supply network. The distribution Transformer is the last in the chain of electrical energy supply to the households and industrial enterprises. These transformers are installed in both rural & urban areas to supply electrical power. The distribution transformers serve the crucial function of transforming of high voltage (11kV) to lower values (433V) to meet the requirements of household appliances and industries.
Operational reliability of distribution transformers is most important for uninterrupted supply of electrical power. Improper use, maintenance and neglect can cause not only premature failure but also heavy financial losses to the distribution companies and inconvenience to the consumers.
The distribution transformers represent substantial capital investment for distribution companies and hence reliability is at most important to avoid loss of revenue resulting from premature failure. In this era of reformation and liberalization of electricity markets, the distribution companies are faced with new challenges of providing uninterrupted quality power supply with minimum cost. In this, endeavor, the distribution companies are looking for appropriate O & M procedures and diagnostic test methods to determine state & condition of the distribution transformers.
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Types of distribution transformers
The Distribution transformers are classified as follows:
1. Naturally cooled out door distribution transformers 2. Naturally cooled sealed distribution transformers 3. Completely self-protected distribution transformers
1. These distribution transformers are oil immersed, naturally cooled 3phase outdoor type transformers of capacities 16,25,63 &100KVA for use on systems with normal voltage of 11KV.
2. These distribution transformers are also oil immersed, naturally cooled 3phase outdoor type sealed transformers of capacities 16,25,63 &100KVA.
3. These distribution transformers are oil immersed, naturally cooled 3phase outdoor type completely self protected transformers of capacities 16,25,63 &100KVA. These transformers are equipped with circuit breakers on LV side, 11KV fuses and 11KV Lightning arresters on 11KV side as integral parts of the equipment.
Distribution transformer failures
The failure of distribution transformers in our country is high. The average failure rate in our country is about 9.2% and in some of the states it is as high as 32%. The revenue losses as a result of distribution transformer failure is unacceptably high
Some of the possible reasons for Distribution transformer failures:
1. Continuous over loading of transformer beyond rated capacity. 2. Improper tap position can cause excessive core loss and consequently excessive heating. 3. Outgoing cable faults if not cleared in specific time. 4. Improper contact of fuses/ over capacity fuses. 5. Loose cable connection to LT busing terminals. 6. Improper/loose earthing connection. 7. Unbalance load conditions. 8. Improper maintenance/checking of oil level in conservator/transformer and not topping up oil
to required level. 9. Non checking of the condition of silica gel/ not changing/reactivating the silica gel if silica gel
has turned pink in colour. 10. Non checking oil level in bottom of breather/forming oil seal and not making up the oil level
when required. 11. Not periodically checking the condition of gasket joints and tightening/replacing gaskets if
needed.
Factors affecting life of a transformer
A) Effect of moisture- Transformer oil readily absorbs moisture from the air. The effect of water in solution in the oil is to decrease the dielectric strength of the oil as well as the insulating paper which absorbs and stores the moisture due to its higher affinity of water over oil. All possible preventive steps should, therefore, be taken to guard against moisture penetration to the inside of the transformers.
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B) Effect of Oxygen- Oxygen may be present inside the transformer due to air remaining in oil, air pockets trapped in the winding, etc. The oxygen reacts with cellulose of the insulation and the decomposition products of the cellulose lead to the formation of organic acid soluble in oil and sludge which block the free circulation of the oil. Care should be taken to eliminate air from transformer by filing the transformer under vacuum.
C) Effect of solid impurities- The dielectric strength of oil diminishes appreciably if minute quantities of solid impurities are present in the oil. New transformer may contain particles of insulating material and other solid impurities. It is therefore, a good practice to filter the oil after it has been in service for a short time.
D) Effect of varnishes- Some varnishes particularly of the oxidizing type, enter readily in reaction with transformer oil and precipitate sludge on the winding. Synthetic varnishes having acid inhibiting properties generally delay the natural formation of acid and sludge in the oil.
E) Effect of slackness of windings- Because of repeated movements of the transformer, coils may be displaced from their original position which can cause electric and magnetic unbalance. It is therefore required that the tie rods or pressure screws should be tightened.
Maintenance:
If a transformer is to give long and trouble free service it should receive a reasonable amount of attention and maintenance. The causes of breakdown of transformers may be classified as follows:-
a) Faulty design or construction b) Incorrect installation, operation and maintenance c) Overload d) Neglect e) Wear and tear and other deterioration f) Accidents g) Failure of auxiliary equipment.
A rigorous system of inspection and preventive maintenance will ensure long life, trouble-free service and low maintenance cost. Maintenance consists of regular inspection, testing and reconditioning where necessaryRecords should be maintained of the transformer, giving details of all inspection and tests made, and of unusual occurrences if any.
The principal objective of maintenance is to maintain the insulation in good condition. Moisture dirt and excessive heat are the main causes of insulation deterioration and avoidance of these will in general keep the insulation in good condition. The limiting factor is the ageing of the insulation and decline in the quality of the insulation during the ageing process due to chemical and physical effects.
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Maintenance procedure
Safety precautions
Before starting any maintenance work the transformer should be isolated from the supply
and the terminals earthed. The level of oil in the transformer should be borne in mind when
undoing nuts and bolts and before unsealing the tank. No fire should be kept near the
transformer while maintenance work is in progress.
Oil
The oil level varies with the oil temperature. The indicator generally show the ‘cold’ level when the oil is at a temperature of about 25 Deg.C The transformer should be topped up as necessary with clean transformer oil. If the oil level drops appreciable over a short period, the tank should be checked for leaks. In case there is a leak on a welded joint, it should be rewelded. A leaking gasket may be attended to by tightening the bolts. If this is not sufficient, the gasket should be replaced.
Conservator
Conservators are so arranged that the lower part acts as a sump in which any impurities entering the conservator can collect. A valve/plug is fitted at the lowest point of the conservator for draining oil. The inside of the conservator should be cleaned every two or three years.
The oil level indicator should be kept clean and examined at regular intervals, and oil should be added.
Transformer body: The transformer tank and other parts should be inspected for any rust or leak. Rusted portions should be cleaned thoroughly and repainted with proper paints. Leaking joints can be rectified by tightening the bolts to the correct pressure or replacing the gaskets.
Bushings: The bushings should be inspected for any cracks or chippings of the porcelain at regular intervals and keep free from dust and dirt. The bushings should be cleaned at regular intervals.
External connections: All external connections should be tight. If they appear to be blackened or corroded, the same can be cleaned or should be replaced. The HT & LT jumpers shall have appropriate size lugs properly crimped for making connections to the transformer terminals
Dehydrating Breather: Breather should be examined to ascertain if the silica gel requires changing. More frequent inspections are needed when the climate is humid and when the transformer is subjected to fluxuating loads. So long as the silica gel is in active stage its colour is blue but as it become saturated with moisture its colour gradually changes to pale pink. The gel should then be replaced or reactivated.
The level in the oil seal must be maintained at the marked level.
Gaskets: Gaskets sometimes shrink during service. It is therefore necessary to check the tightness of all the bolts fastening gasketed joints. Leaking gaskets should be replaced.
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Inspection and maintenance schedule: The frequency of inspection should be determined by the size of the apparatus. Local climatic and atmospheric conditions will also influence inspection schedule.
Following table may be used as a guide for determining the inspection schedule ( CBI&P Manual on Transformers)
Recommended inspection schedules for transformers rating less than 1000KVA are given in table.1
S Inspection frequency
Item to be Inspected
Inspection notes Action required if inspection shows unsatisfactory conditions.
1. Hourly i)Load (amperes)
ii) Temperature
iii) voltage
i) Check against rated figures
ii) Oil temperature and ambient temperature
iii) Check against rated figures
-----
-----
-----
2. Daily Dehydrating breather
i) Check that air-passage are clear.
ii) Check colour of active agent
If silica gel is pink, change by spare charge. The old charge may be reactivated for use again.
3. Monthly i) Oil level in transformer
ii) Connections
i) Check transformer oil level
ii) Check tightness
i) If low, top up with dry oil, Examine transformer for leaks.
ii) if loose, tighten.
4. Quarterly Bushings Examine for cracks and dirt deposits
Clean and replace.
5. Half yearly i) Non-conservator transformer.
ii) cable boxes, gasketed joints, gauges and general paint work
Check for moisture under cover inspect
Improve ventilation, check oil.
6. Yearly
i) Oil in transformer
i) Check for dielectric strength and water content. Check for acidity and sludge
i) Take suitable action to restore quality of oil.
ii) Take suitable actions
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ii) Earth resistance
iii) Relays, alarms the circuits,etc
ii) ----
iii) Examine relay and alarm contacts, their operation, fuses, etc. Check relay accuracy, etc
if earth resistance is high.
iii) Clean the components and replace contacts and fuses if necessary,
iv) Change the setting, if necessary.
7. 2Yearly Non-conservator transformers
Internal inspection above core
Filter oil regardless condition.
8. 5 Yearly -------- Overall inspection including lifting of core and coils
Wash by hosing down with clean dry oil.
Location of distribution transformers
The installation site should be such that there is easy accessibility for inspection. The transformer installation position should be such that the breather, oil level indicator, rating and diaphram plate, dial thermometers etc., can be safely examined with the transformer energized. It should also be possible to have access to the operating mechanisms of the on load tap changer/ off circuit tap switch, marshalling box etc. The sampling valve, drain valve etc. should be of convenient locations.
When transformers are installed indoors, proper ventilation should be provided and adequate
space should be provided to enable it to dissipate the losses properly. If adequate spacing is
not provided, the temperature of the transformer will increase, and this will adversely affect
the insulation of the winding and the condition of the oil.
Foundation
Special foundation is not required for the installation of a distribution transformer, except a level floor strong enough to support the weight and to prevent accumulation of water. The transformer foundation should be provided with adequate oil soak pits and drains.
For outdoor installations, a level concrete plinth of correct size to accommodate the transformer in such a way that no person may step on the plinth, should be provided for transformers.
Condition monitoring and O & M measures:
The distribution transformers, being so large in nos. and scattered all over the places, it is
impossible to exercise the same amount of monitoring/ care like that for power transformers.
However load monitoring of each distribution transformer is carried out once a year and load
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23
balancing/ relieving of overloaded transformers, to the extent possible, is carried out as a
follow up action, Pre-festival check for any oil leakage/ low oil level/over-heated joints for
distribution transformers, at strategic locations are also carried out for taking necessary
corrective actions.
Exhaustive database on make, year of purchase, technical details, peak load reading, accessories, date of commissioning, location, history of maintenance/repairs etc. and performance shall be maintained. All failed transformers are inspected thoroughly prior to repair/disposal with a view to finding out the probable cause of failure, since such inspection provides vital feedback on design/manufacturing deficiency or any abuse that it might have been subjected to. Depending on the outcome of such inspections, review and amendments of specification are initiated.
Following are the diagnostic tests recommended for condition assessment of the Distribution Transformers.
a) On-line Diagnostic tests
Sl. no Tests Detection capability
1. Infrared thermo imaging Detects hot spots.
2. Transformer oil analysis Healthiness of oil
Internal condition
b) Off- line Diagnostic tests.
Sl.no
Tests
Detection capability
1.
Insulation Resistance
Winding Resistance
Transformer Turns Ratio
Tan delta
Index of dryness
Loose/damage of conductor.
Shorted turns &open winding
Dielectric Losses
Care to be exercised to avoid failures:
Sl.no In Manufacturing Stage In Transport In Working Conditions
1.
2.
3..
Proper insulation arrangement
Mechanical rigidity to withstand heavy forces
Adequate cooling arrangement
Safe handling during transport and erection
Adoption of standards for Erection of transformer
Standard construction
Maintenance of oil level
Maintenance of Breather with silica gel & oil seal
Periodical testing of IR values
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4.
5.
6.
7.
Adequate quantity of oil for insulation & cooling
Maintaining atmospheric pressure inside with pure air
Rigid fixing of core-coil
Adequate earthing of core & other metallic parts
Periodical tests on transformer
Earth resistance values and earth maintenance
Keeping standard voltage & frequency at load terminals.
Maintaining lightining arresters to prevent damage due to surges
Maintaining LT system
Keeping the loading within the limits
Examination of failed distribution transformers:
Sl.no
External Check up
Internal Physical
Verification
1.
2.
3.
4.
5.
Oil level and quantity available
Places of oil leakage
Condition of Breather &Silica gel
Condition of Bushing & Bushing rods
Condition of vent Diaphragm
Condition of Valves
Conditions of HT coils in all the three phases
Check lead connection from coil (Delta &Star points)
Condition of core
Condition of Tap switch and connections
Condition of core earthing
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25
6.
7.
8.
IR value & continuity
BDV Test on oil
Presence of sludge & moisture in oil & physical condition of oil
Protection of distribution transformers:
Pole mounted distribution transformers of capacities ranging from 16kVA to 200kVA
with voltage ratio of 11000/433-250 volts shall have protection as given in Table below.
Voltage ratio Capacity (KVA) Protection
Primary side Secondary side
11000/433-250
Volts
16,25, 63,100
&200
Drop out/ Horn gap fuse Moulded case
circuit breaker
(MCCB)
Ground mounted distribution transformers of capacities ranging from 200KVA to 3150KVA with voltage ratio of 11000/433, 33000/433 and 33000/11000 volts shall have the protection as given in Table below.
Voltage ratio Capacity KVA Protection
Primary side Secondary side
11000/433-250 315,630,1000,and 1600 HRC/Expulsion fuse MCCB
33000/433 630,1000,1600 HRC/Expulsion fuse MCCB
33000/433 1600 HRC/Expulsion fuse CB
Concept of AT&C losses and Measures for reduction of AT&C losses
Viji Bharathi, Engineering Officer, Distribution Systems Division, CPRI
Introduction
Electricity Distribution plays a vital role in the social and economic development of our
society. It has a great impact on the quality of life of a common man. There is a vast gap
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26
existing between the demand and supply of electricity. Various schemes like APDRP, R-
APDRP, RGGVY etc., are put forth by the Govt. of India to address the existing demand-
supply gap. The Government of India also came up with an ambitious target of―Power for all
by 2012‖ under the National electricity Policy.
Transmission & Distribution (T&D) Loss
The difference between the Energy Input and the Energy Sales which is the Energy loss is
termed as the Transmission and Distribution (T&D) loss. The State Electricity Boards are
characterized by the T&D loss.
Energy loss = Energy Input-Energy Sold =
T&D loss
Due to lack of adequate investment in the T&D works, the T&D losses have been on the
higher side and reached to the level of 32.86% in the year 2000-2001. The reduction of these
losses was essential to bring economic viability to State utilities.
Overview
ARR is termed as the Average Rate of Realization of Revenue from the sale of Energy.
ACS is termed as the Average Cost of Supply at which the Energy is purchased from
transmission for distribution to end user.
The gap between the Average Rate of Realization (ARR) and the Average cost of supply
(ACS) has been constantly increasing till 2000-01. This gap was causing the state electricity
boards (SEB) run under huge revenue losses.
In view of the losses faced by the SEB's, the Government of India/MoP has undertaken
reforms in power sector with a step by the Electricity Act 2003 and then through the
Accelerated Power Development Programme (APDP) that was renamed as the Accelerated
Power Development and Reforms Programme (APDRP) in 2001-02. The main aim of
APDRP was restoring the commercial viability in the distribution sector.
Concept of AT&C loss
As the T&D loss was not able to capture all the losses in the network, concept of Aggregate
Technical and Commercial (AT&C) loss was introduced. AT&C loss captures technical as
well as commercial losses in the network and is a true indicator of total losses in the system.
High technical losses in the system are primarily due to inadequate investments over the
years for system improvement works, which has resulted in unplanned extensions of the
distribution lines, overloading of the system elements like transformers and conductors, and
lack of adequate reactive power support.
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27
The commercial losses are mainly due to low metering efficiency, theft & pilferages. This
may be eliminated by improving metering efficiency, proper energy accounting & auditing
and improved billing & collection efficiency. Fixing of accountability of the personnel may
help considerably in reduction of AT&C loss.
AT&C loss = 1-(Billing Efficiency*Collection Efficiency) =
(Energy Input – Energy realized) * 100
(Energy Input)
where, (i) Energy Realized (MU) = Collection Efficiency * Energy Billed
(ii) Collection Efficiency= Revenue Collected (Crores) *100
Revenue Billed (Crores)
(iii) Billing Efficiency (%)= Energy Billed (MU)* 100
Energy Input (MU)
The two main components of AT&C loss are (i) Technical loss and (ii) Commercial loss.
Technical Loss
Every element in a power System (a line or a transformer etc) offers resistance to power flow
and thus consumes some energy while performing the duty expected of it. The cumulative
energy consumed by all these elements is classified as ―Technical Loss.‖
Commercial Loss
Losses occur on account of non-performing and underperforming meters, wrong applications
of multiplying factors, defects in CT & PT circuitry, meters not read, pilferage by
manipulating or by passing of meters, theft by direct tapping etc. These are all due to non-
metering of actual consumption and are called commercial losses. The total of ―Technical‖
and ―Commercial‖ losses is termed are T&D loss. It is unfortunate that in addition to the
above, there is also a loss in revenue due to non-realisation of billed demand. This is in
addition to commercial losses and the aggregate of T&D loss and revenue loss due to non-
realisation is termed as ―AT&C loss‖ (Aggregate technical and Commercial loss).
Therefore AT&C loss to the utility is the sum total of technical loss, commercial losses and
shortage due to non-realisation of total billed demand.
Typical Example
Let the Energy Input be 100MU and the Energy Billed be 70MU.
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28
Then, T&D loss = 100-70 = 30MU and % T&D loss = 30%.
Let‘s say, the Revenue is billed (Revenue demand) for 70MU, while the Revenue collected is
only for 90% of the billed energy, i.e. 0.9*70 = 63MU.
Then, AT&C loss = 100-63 = 37MU and% AT&C loss = [1-(Billingefficiency*Collection
efficiency)] *100 = [1-(0.7*0.9)] *100 = 37%.
Factors contributing to High Technical Losses
The main factors that contribute for high technical losses are:
(i) Lengthy Distribution Lines: The primary and secondary distribution lines in rural areas
usually extend over long distances and are mostly radially laid. This results in high line
resistance and therefore high I2 R losses in the line.
(ii) Inadequate Size of Conductors:Rural loads are usually scattered and generally fed by
radial feeders. The conductor size of these feeders should be properly selected.
The size of the conductor should be selected on the basis of kVA x KM capacity of standard
conductor for required voltage regulation.
Tables 1 & 2 below indicate the length of lines for 11kV and 415 volts corresponding to
different loads for the voltage regulation prescribed by IE Rules; for different sizes of
conductors respectively.
Table 1
Length of 11kV line
Size of
Conductor
(with Code No.)
kVA-KM for 8%
voltage drop at 0.8
pF
Maxi-mum
length of line
(kM)
Load that can be
connected (kW)
50 MM2 ACSR
Rabbit 10,640 30 355
30 MM2 ACSR
Weasel 7,200 20 360
20 MM2 ACSR
Squirrel 5,120 15 341
Table 2
Length of 415V line
Size of conductor
(with Code No.)
kVA-km for 8%
voltage drop at 0.8
pF
Maxi-mum length
of line (kM)
Load that can be
connected (kW)
30 MM2 ACSR
Rabbit 11.76 1.6 7.35
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The figures of Table 1 &2 are for a conductor temperature of 60° C. For a conductor
temperature of 50° C, the above figures shall be about 3% higher and for a temperature of 70°
C about 3% lower.
(iii) Distribution Transformers (DTs) not located at Load Centre: Rural loads are usually
scattered and generally fed by DTs not Located at Load centre on the Secondary
Distribution System.Consequently, the farthest consumers obtain an extremely low
voltage even though a reasonably good voltage level is maintained at the transformers‘
secondary. This again leads to higher line losses. (Decreased voltage at the consumer
terminals lead to increased losses).
Therefore in order to reduce the voltage drop in the line to the farthest consumers, the
distribution transformer should be located at the load centre to keep voltage drop within
permissible limits and thus minimize the losses.
(iv) Over-rated Distribution Transformers leading to under-utilization: Studies on 11 kV
feeders have revealed that often the rating of DTs is much higher than the maximum
kVA demand on the feeder. Over rated transformers draw unnecessarily high iron losses.
In addition to these iron losses in over rated transformers the capital costs locked up is
also high.
From the above it is clear that the rating of DT should be judiciously selected to keep the
losses within permissible limits. For an existing distribution system the appropriate capacity
of a DT may be taken as very nearly equal to the maximum kVA demand at good PF (say
0.85). Such an exercise has been carried out for a number of distribution systems and
transformers with capacity of 25, 63,100,160, 315 kVA are standardized for different systems
varying with power factors and diversity factors.
(v) Low Voltage (less than declared voltage) at Transformer and Consumer Terminals:
Whenever the voltage applied to induction motor is varied from the rated voltage, its
performance is affected. Within permissible voltage variation of +/- 6% in practice, the
supply voltage varies by more than 10% in many distribution systems. A reduced voltage
in case of induction motor results in higher currents drawn for the same output.
For a voltage drop of 10%, the full load current drawn by the induction motors increase
by about 10% to 15%, the starting torque decreases by nearly 19% and the line losses in
the distributor increases by about 20%.
As the bulk load of rural areas and small scale industrial areas consists of induction
motors, the line losses in the concerned distribution systems may even touch 20%.
The above situation is corrected by operating an "on-load-tap changer" in the power
transformer situated at 66/11 kV high voltage sub-stations and 33/11 kV sub-
stationsandby providing a combination of switched capacitors and automatic voltage
regulatorson the 11 kV feeders
20 MM2 ACSR
Weasel 7.86 1.0 4.86
13 MM2 ACSR 5.58 1.0 5.58
30 MM2 AAC ANT 12.06 1.6 7.54
16 MM2 AAC Gnat 6.96 1.0 6.96
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30
Further, the "off load tap changer" in DTs is adjusted prior to the commencement of
agricultural load season which is readjusted before the on-set of monsoons when the
rural load is small if the off-load tap changing gear is available.
(vi) Low Power Factor:In most of the LT distribution circuits, it is found that the PF ranges
from 0.65 to 0.75. A low PF contributes towards high distribution losses. For a given
load, if the PF is low, the current drawn is high. Consequently, the losses that are
proportional to the square of the current will be more.
Thus, line losses owing to poor PF can be reduced by improving the PF. This can be done by
installing shunt capacitors.
Shunt capacitors can be connected in the following ways:
Shunt capacitors are connected on the secondary side (11 kV side) of the 33/11 kV power
transformers.
Line losses in LT distribution lines may also be considerably reduced by installing shunt
capacitors of optimum rating at vantage points as decided during load stations.
The optimum rating of capacitor banks for a distribution system is 2/3rd
of the average
kVAR requirement of that distribution system. The vantage point is at 2/3rd
the length of the
main distributor from the transformer.
A more appropriate manner of improving the PF of the distribution system thereby reducing
the line losses is to connect capacitors across the terminals of the motors (inductive load).
Many electricity supply authorities are making it compulsory for the consumers to provide
capacitors of adequate rating for all types of installations with connected loads of 5 HP and
above.
(vii) Bad Workmanship Resulting in Poor Contacts at Joints and Connections: Bad
Workmanship contributes significantly towards increase in distribution losses. The
significance leads to:
Joints are a source of power loss. Therefore the number of joints should be kept to
minimum. Proper jointing techniques should-be used to ensure firm connections.
Connections to the transformer bushing-stem, drop-out fuse, isolator, LT switch etc,
should be periodically inspected and proper joint ensured to avoid sparking and heating of
contacts.
Replacement of deteriorated wires and services should also be made timely to avoid any
cause of leakage and loss of power.
Haphazard and adhoc planning which ignore scientific methods also lead to high technical
losses.
Measures to reduce technical loss:
Short term measures:
(i) Network Re-configuration:
The term network reconfiguration includes any one or all the works such as:
Formation of new links to minimize within a feeder to form a tree structure.
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31
Erection of interlinking lines to change the area of feed from one substation to another
and balance the load among the substation.
Bifurcation of existing feeder to form parallel paths of power flow.
Network reconfiguration among feeders is effective only when the voltage drop between the
nodes to be linked is rich and the distance between the nodes is short. The nodes to be linked
have to be selected taking the quotient of voltage difference and the distance between the
nodes as criteria. Network reconfiguration within a feeder is effective only when zig-zag
factor is high. Zig-zag factor is defined as the ratio of total length of feeder to the bee line
distance between the Distribution substation and minimum voltage point. The links have to
be chosen so as to create a tree structure.
The distribution network in developing countries was expanded in adhoc manner to minimize
the initial investment cost; and longrange planning studies are not generally undertaken. This
situation has given a vast scope for reconfiguring the network to minimize losses.
(ii) Reactive power control: (a) Shunt Compensation: The load incident on the distribution system is mostly inductive,
requiring large reactive power. The best method is to compensate the reactive power at
the load end itself but it is difficult to implement in practice. Hence, providing
compensation on the distribution system is essential. The shunt capacitor supplies
constant reactive power at its location, independent of the load. So, optimal compensation
provided for peak load condition may result in over compensation during light load
conditions, necessitating automatic switching schemes. The problem of determining the
number, size and location of shunt capacitors required to be provided is formulated as an
optimization problem. Objective function is the cost of energy saved due to reduction of
power losses by the installation of capacitor banks less the annual cost of capacitors
installed. The voltage constraints need not be considered, as the capacitors are switched
on and off along with load to avoid over voltage during low load operation; and capacitor
alone cannot economically improve the voltage during peak load period to satisfy the
statutory lower limit.
(b) Series Compensation:The maintenance of voltage at customer premises within statutory
limits at all loads is the responsibility of utility. Series capacitor introduces negative
reactance in the line and improves the voltage which in turn also reduces the power
losses. The main advantage of series capacitor is the quantum of compensation is highly
responsive of series capacitor is that the quantum of compensation is highly responsive to
load current and series capacitor can be kept in the circuit during the complete load
cycle, without causing any adverse effect of over voltages, during low load conditions.
The problem of determination of optimal location and capacity of series capacitor is
formulated as an optimization problem. The objective function is similar to that of shunt
compensation. The voltage constraint is that the voltage at the location of capacitor shall
not exceed permissible upper is less than the difference between the permissible upper
limit of voltage and voltage at the location of capacitor without series capacitor. Solution
to the problem of determination of optimal capacity and location of series capacitor is
obtained through an interactive approach.
(iii)Network Re-conductoring:
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32
Network Re-conductoring is replacement of the existing conductor on the feeder with optimal
conductor size for optimal length of the feeder. This scheme arises where existing conductor
is no more optimal due to rapid load growth. This is particularly relevant to developing
countries, where annual growth rates are high and the conductor sizes are chosen to minimize
the initial capital investment. Studies of several distribution feeders indicate that the losses in
the first few main sections (4 to 5 say) from source constitute a major part of the losses in the
feeder and by reinforcing these sections with conductor of optimal size, the losses can
minimize the total cost, that is, cost of investment and cost of energy losses over a period of 5
to 10 years.
(iv) Automatic Voltage Booster:
The functioning of Automatic booster (AVB) is similar to that of series capacitor. AVB is an
on load tap changer. It boosts the voltage at its point of location in discrete steps and this in-
turn improves the voltage profile and reduces the losses in the section beyond its point of
location towards receiving end. An AVB generally has a total voltage boost of 10% in four
equal steps. The loss reduction is directly proportional to voltage boost and maximum
permissible voltage boost is limited by the difference between the permissible maximum
voltage and voltage at the point of location of AVB. The problem of determination of optimal
location and percentage of boost of boost of AVB is formulated as an optimization problem.
The objective function is the cost of energy saved due to desirable constraints is that the
voltages at all sections should not exceed the statutory upper and lower limits. An interactive
type of algorithm is adopted in the proposed solution approach.
(v) Maintenance Schedule:
Strict terms to adhere to implement the scheduled maintenance practices for various
distribution network components like Power transformers, distribution transformers should be
framed. The distribution utilities generally have a schedulefor maintenance. The only
constraint would be that these maintenance schedules are not put in practice regularly.
(vi) Software tools:
Software tools may be used to identify the network reconfiguration which results in
maximum LRVI (loss reduction and voltage improvement) with least investment. Based on
cost benefit ratio, the best option for investment can be chosen. A combination of GIS and
network analysis tools like Power Net may be adopted.
As a last resort, to go in for another sub-station followed up by reconfiguration.
In addition to the above which is a general up-gradation of the distribution network,
thefollowing measures may be adopted to reduce the technical loss.
(vii) High Voltage Distribution System (HVDS): Whenever there are widely distributed and sparse consumers on an LT feeder involving long
lines to the load, the line losses (I2R losses) become very high. It is more practical to use
high voltage (11kV) distribution of power to such remote loads thereby reducing the line
losses as the equivalent HV current is of a much lower magnitude. The first attempt at
HVDS was for a single phase 11kV and a neutral wire feeding small capacity like
5/10/15kVA transformers with a primary of 6350V and secondary of 230V powering
individual single phase pump sets. This was area specific and therefore resulted in unbalance
CPRI-Training Notes
33
in the power transformer feeding the HVDS. Secondly, there was slight voltage drop at the
end of the line on load resulting in lower secondary voltage. One method used by APSEB
was to repair single phase copper wound transformers with aluminium HV windings thereby
boosting the secondary voltage. With judicious loading of the power transformer, HVDS is
an attractive distribution method where the loads are distributed widely and removed from
power transformer.
(viii) Amorphous Core Transformers:
Amorphous Core Transformersmay be used where the core magnetizing or no-load loss gets
substantially reduced. They are not economical at present. Efforts are being made to make
amorphous core material indigenously and the cost is expected to go down considerably.
Factors contributing to Commercial Losses:
The main causes for commercial loss can be grouped into two. (i) Due to the deliberate action
of the regularized/ unauthorized consumers and (ii) Due to internal shortcomings of the utility
system/policy
Deliberate action of consumers
Unscrupulous consumers extract energy illegally which is the act of Pilferage of energy.
Energy pilferage is done by direct tapping by the non-customers and by the existing
customers.
In certain areas, direct tapping of power by non-customers is widely prevalent. This is mainly
in domestic and agricultural categories. Geographical remoteness, mass basis for theft, poor
law enforcement capability and inaction on the part of utility are helping this phenomenon.
Theft by existing consumers is by various means such as totally bypassing the meter,
tampering the meter in different ways, etc. New methods are being constantly evolved.
Internal shortcomings of the utility
This prevails mainly due to Metering, Billing and Collection inefficiencies.
Metering: There are many services unmetered. The meters get sluggish over a period of
time. Many stuck up meters are allowed for years. There is considerable voltage drop in
metering cables. The meter capacity and the load have no relation.Manual errors in meter
reading such as no readings furnished by the meter reader for a good number of services,
constant ‗nil‘ consumption cases reported without any comment, progressive readings in
disconnected services, etc.Wrong multiplication factors (MF) are adopted. After the MF is
changed, it is not intimated to the billing agency.
Billing: There are reasons such as non-receipt / late receipt of bills, wrong bills, wrong
calculations, and manual errors in billing etc.contributing to commercial losses.
CPRI-Training Notes
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Collection: Bad payment history, regular defaulters, over dues, long dues by the Government
departments and Subsidies by Governments to distribution utilities and wrong tariff category
with respect to the connected load/ sanctioned load are some of the reasons for commercial
losses.
Measures to reduce the Commercial loss
A good distribution network shall be in place for providing reliable power supply at assured
voltage levels to consumers and the same shall be with least technical losses. The commercial
losses can be reduced by accurate metering, efficient billing and prompt collections
implementing.
Accurate Metering (A metering plan for installing meters with sustained accuracy).
Appropriate range of meter with reference to connected load.
Electronic meters with (Time of day, tamper proof data and remote reading facility) for
HT & HV services.
Intensive inspections by pooling up staff.
Reduce meter exceptional.
Use of Energy Audit as a tool to pinpoint areas of high losses.
Eradication of theft.
Automated Meter Reading (AMR) systems.
Measures to reduce Power pilferage
Electricity theft can never be totally eradicated in any power system. Setting-up of the
strengthened Vigilance and Raids with police enforcement help curtail power theft.Electricity
theft and corruption appear to be closely linked. To curb theft, a combination of strong
technical improvements with intelligent and active anti-theft remedial measures is to be
introduced. Imprisonment, heavy fines are to be levied for compounding. Some change in
the value systems of the society is also needed. The opinion makers and social leaders are to
be involved to effectively tackle this massive social evil.
Analysis on very high consumption when compared to the similar connected loads and
continuous monitoring on abnormal variation in consumption help detect unauthorized
additional loads through special tools.
Electricity Act 2003 has brought radical changes in all the facets of the electricity sector.
Though originally the vigilance wing was meant only for detection of pilferage, of late its
functions also cover many other facets like:
Malpractice
Back billing
Excess connected loads
Poor power factors in all categories
Running of captive generator sets without adequate safety arrangements etc.
Non sealing of AB switches, meter boxes, and terminal covers.
Line losses in selected towns, industrial feeders etc.
Functioning of border meters, capacitor banks etc.
Bus, P.T. and C.T. facilities for efficient metering.
Inspection of high value UDC services.
Study of MRBs.
CPRI-Training Notes
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Applying CAT for HT & LT services and inspecting class F services, etc.
Maintenance of assets by local officers.
Billing irregularities in transformer repairs, maintenance and construction works.
Nonstandard releasing of services.
Releasing of services in UDC premises.
Releasing of services in wrong categories.
Coordinating massive inspections with all engineers and APTS personnel wherever required.
Involvement of employees in various irregularities.
Payment and billing pattern of services of VIPs.
Effective implementation of law with the aid of Electricity Act 2003 can eradicate / mitigate
theft which forms substantial portion of the commercial losses.
Administration should be reformed to bring out improved transparency, greater
accountability and streamlining the structure eliminating all forms of corruption for corporate
governance.
To overcome the shortcomings of the utility
Adoption of Common billing software and application of the Consumer Analysis Tool (CAT)
to have a meaningful control, review, storage and retrieval of the consumer data base.
Increased customer convenience such as drop box facility, Any Time Payment (ATP) options
etc. shall be the guiding factor for smooth collections to increase the revenue.
Effective disconnection of defaulters, target on high arrears services, immediate action of
non-paying consumers, compulsory and immediate prosecution in case of bounced cheques,
computerized monitoring system, adoption associations, cooperatives, panchayats and
franchisees for rural electricity management are some of the measures
There are many services unmetered. A large scale drive is necessary to bring all
unauthorized consumers on to the rolls. The meters tend to get sluggish over a period of
time. Old meters are to be replaced in a phased manner by high accuracy meters, especially
for high value services.
Electronic meters should be put to use. These meters with no moving parts, there is no wear
and tear in service. Due to its in-built intelligence, several features/ measurements such as
kWh, kVA, kVAR, PF, Currents, Voltages, detection of theft and tampers are possible. They
are able to withstand the harsh environments of heat, humidity, dust, shock, vibration, EMI/
EMC and magnetic field. Post processing of data can detect theft.
Use of remote metering, the remote metering also called as the AMR (Automated Meter
Reading) is an entire system that does away with manual reading and billing of consumers.
Most of manual errors due to meter reading and billing can be curtailed through proper
metering system thereby reducing the commercial losses.
CPRI-Training Notes
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Aerial Bunched Cables (ABC):
The use of ABC avoids power pilferage due to insulation as compared to bare LT lines thus
reducing the commercial losses and provides better safety and reliability.
Effective metering, billing and collectionactivities
The commercial losses can be reduced by accurate metering, efficient billing and prompt
collection implementation, Use of Accurate Metering (A metering plan for installing meters
with sustained accuracy), Use of appropriate range of meter with reference to connected load,
Use of Electronic meters with (TOD, tamper proof data and remote reading facility) for HT &
HV services, Use of common billing software, Establish accurate data base of the network
and Consumer Indexing, Intensive inspections by pooling up staff to reduce (a) direct tapping
for power pilferage (b) defective metering, timely billing and collection activities (c) to check
on the relevant tariff of the connected category
Energy Audit:
Energy Audit practice may be adopted as a tool to pinpoint areas of high losses. Special
drives to inspect the rating of the Irrigation pump sets in the agricultural sector should be
adopted. All the un-authorized consumers are to be regularized in a phased manner to
contribute towards reducing the commercial losses.
References:
[1] ‘Modernisation of Power Distribution’ (Book) (Focus on APDRP) by M.V.S.
Birinchi, March – 2004
[2] Lecture notes from ‗DRUM Training Program’, CPRI Bangalore
[3] ‗Emerging Technologies for Distribution Loss Reduction (HVDS, ABC, Metering-
Electronic, Prepaid, SCADA & DA) by M.V.S.Birinchi, Core International Inc.
[5] ―Electricity Theft vis-avis Revenue Protection‖ a comparative analysis by Er.Vinay
Gupta, cover story IEEMA Journal, May 2014
[4]Web site: www.powermin.nic.in, www.apdrp.gov.in
CPRI-Training Notes
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Reactive Power Management
R.A.Deshpande, Joint Director, Distribution Systems Division, [email protected]
The main objective of the power system is to meet the connected load to the maximum extent,
meeting the constraint of all the available generations in efficient, economic and reliable
manner. The power system consists of generating stations, transmission and distribution
networks and the loads. The load consists of both active and reactive parts and it absorbs
both active and reactive power. The transmission & distribution network does not generate
active power but can absorb or supply the reactive power. Some active power is lost in this
system in form of transmission/distribution losses. Generators either absorb or generate the
reactive power based on the excitation voltage.
The concept of reactive power, it’s significance and impact on overall power system, different
means to control the reactive power will be explained in this lecture.
Introduction
Real power accomplishes useful work while reactive power supports the voltage that must be
controlled for system reliability. In AC systems voltage and current pulsate at the system
frequency. Although the voltage and current frequency of pulsating may be the same, their
peak occurs at different time. The power is algebraic product of voltage and current. Real
power is the average of power over cycle and measured by volt-amperes or watt. The portion
of power with zero average value called reactive power measured in volt-amperes reactive or
vars.
In steady state operation of electrical power systems, both active power and reactive power
balances must bemaintained.
The reactive power generated by synchronous machines and shuntcapacitances must beequal
to thereactive power of the loads plus the reactive transmission losses. If the active power
balance is not kept, thefrequency in the system will be influenced, while an imbalance in
reactive power can result in abnormalvoltagesin the system much beyond permissible ones.
The voltage in a system is stronglyaffected by the reactive power flow. Consequently the
voltage can be controlled to desired values, by control ofthe reactive power. Increased
production of reactive power gives higher voltage in the vicinity of the productionsource,
while an increased absorption of reactive power gives lower voltage.
Power flow is always measured with respect to the voltage. The voltage at the point of
measurement is taken as reference vector for defining the direction of power flow. The
angular position of the current vector defines the direction of active, reactive and apparent
power flow.
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Basic Definitions
1] Real Power:
When a passive linear component is excited by sinusoidal voltage
𝑣 𝑡 = 𝑉𝑚𝑎𝑥 cos(𝜔𝑡)
The resultant current will be
𝑖 𝑡 = 𝐼 max cos(𝜔𝑡 + ∅)
The magnitude of I max and the phase shift Ø will be determined by the application of
ohms‘s law.
And fundamental definition of power is
𝑝 𝑡 = 𝑣 𝑡 ∗ 𝑖 𝑡
The typical voltage and current waveforms are shown in Fig.1
The instantaneous power will be
𝑝 𝑡 = 1
2 𝑉𝑚𝑎𝑥 𝐼 max cos ∅ + cos 2𝜔𝑡 + ∅
Fig.1: Voltage and current waveforms
Fig.2 shows waveform of power in a inductive circuit. If this waveform is seen carefully, few
interesting things can be observed. The frequency of power waveform is double that of
voltage or current. Also it is not symmetrical with respect to x-axis.
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
y
Voltage Current
Main : Graphs
0.210 0.220 0.230 0.240 0.250 0.260 0.270 0.280 0.290 0.300 ...
...
...
-0.020
-0.010
0.000
0.010
0.020
0.030
0.040
y
Pow er
CPRI-Training Notes
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Fig.2: Waveform of ―Power‖
This waveform can be shown to be consisting of two distinct waveforms as shown in Fig.3,
one which is symmetrical to x-axis and the other which is always above x-axis. In other
words the avearge value of first one will be zero and that of second waveform will be always
positive. Here one should not confuse with negative sign put for the power which is to denote
the direction of power flow.
Fig 3: Apparent power consisting of active
power and reactive power
Thus the formula for different powers will be
𝑃 = 𝑃 max (1 − cos(2𝜔𝑡)
𝑄 = 𝑄𝑚𝑎𝑥 sin(2𝜔𝑡)
𝑆 = 𝑃 + 𝑗 𝑄
And in terms of voltage and current
𝑆 = 𝑉 𝐼*
The power triangle shows this concept in pictorial form.
Where P, Q and S are real, reactive and apparent power respectively; V & I are the complex
―root mean square‖ phasor representation of voltage and current and * denotes conjugation.
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
Po
wer
time
Active Power Reactive Power
CPRI-Training Notes
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The direction of power flow depending on angle between voltage and current is illustrated in
Fig.4
Fig.4: Active/Reactive Power Flow with
different angles between voltage and
current
Need for Reactive Power Management
When there islight loading, the system generates reactive power that must be absorbed, while
at heavy loading the systemconsumes a large amount of reactive power that must be injected.
Injecting reactive power into the system raisesvoltages, and absorbing reactive power lowers
voltages.
It is necessary to manage reactive power at all the three distinct points of power system. At
the consumer end the electric equipment are designed to operate within a range of say ± 5 %
or 10 %. At the low voltages many of these perform poorly. The simplest light bulb will glow
dimply giving poor illumination. Induction motors get overheated and get burnt. Sensitive
electronic equipment may not operate at all. Similarly high voltages can damage the
insulation and equipment and also shorten their life-time.
In the transmission network, to maximise real power flow, reactive power flow control is
important.
Reactive power production/absorption can limit a generator‘s real-power producing
capability.
Due to excessive reactive power flow in the system, total current will be higher. This will
result in excessive heating of equipment in addition to undesirable voltage levels.
Surge Impedance Loading
It is very important to refresh the basic concept of Surge Impedance Loading (SIL).The Surge
Impedance Load (SIL) of a lossless transmission line isthe amount of load delivered to a pure
resistance equal to the characteristic impedance (square root ofL/C where L and C are the
incremental distributed series inductance and shunt capacitance). A line with 1.0SIL loading
will have a flat voltage profile (same voltage at sending end and at receiving end), and the
same current all along the line. The voltage and current will be in phase along the entire line.
CPRI-Training Notes
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The reactive powerinto the line from the shunt capacitance charging is exactly equal to the
reactive power consumed by the series inductance losses.
Table 1 : Surge Impedance Loading
The above Table.1 gives SIL loading value for different voltage levels and appropriate size
and the number of the conductors used. The information in Table 1, is taken from CEA.
There are three constrains in transmitting the power over transmission line. Thermal limit,
voltage drop limit and stability limit. For short length of lines thermal overloading is more
significant. Voltage drop constraint is important for medium length of lines. For long lengths
line, steady state stability limits the maximum power transfer. The electrical distribution lines
are never long length lines. Hence thermal heating and voltage drops are only the main
concern in planning or augmenting the electrical distribution system.
Problems of reactive Power
The extension of the above equations lead to
𝑆 = 𝑃2 + 𝑄2
Power factor = cosØ = 𝑃
𝑄
Suppose there are two loads each of 460kW but one with unity power factor (like purely
heating load) and other with power factor of say 0.5 (like induction motor). For simplicity we
will assume that both are single phase load and voltage at the load point is 230 V rms.
For load A,
S = P = 460 kW
I =S/V= 2 A rms
For load B,
S = P / cosØ = 460/0.5 = 920 kVA
I = S/V = 4 A rms
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So if power factor is low then the current increases for the same kW load. The I2R losses in
distribution line will increase four times in this example. If there is single power distribution
line between substation transformer and this load of say resistance 4 ohms, the sending end
voltage in first case will be 238 Volts rms. If 230 V is taken as limiting value then sending
end voltage will be more by 3.47 % in first case. But with low factor load, voltage will go up
by 6.96%. It may be noted that in both the cases meter at load point will be reading 460 W.
As there is no billing for reactive power, consumer pays same amount but the detrimental
effect on distribution system is very much pronounced.
When the example is extended to real electrical distribution network, calculation becomes
difficult. Standard International software and expertise to use it, can give very accurate
results by simulation of any big network. One such example is brought out in Fig.5 and
results tabulated in Table.2.
Fig 5 : Typical scaled down Feeder
Power Factor 0.95 0.75
Total losses 5.52 kW 8.52 kW
Tail End voltage 10.91 kV 10.87 kV
Table 2 : Simulation results of selected feeder
DISCOMs correct for power factor around industrial complexes, or they inform the offending
customer to do so else charge for reactive power. They‘re not worried about residential
service because the individual impact is not visible as in heavily industrialized areas. But
when many domestic consumers added together, power factor correction assists the electric
company by reducing demand for electricity, thereby allowing them to satisfy needs
elsewhere.
Means of controlling Reactive PowerShunt reactors are used to compensate for the effects of
linecapacitance, particularly to limit voltage rise on open circuit or lightload.They are usually
required for EHV overhead lines longer than 200 km.
CPRI-Training Notes
43
A shorter overhead line may also require shunt reactors if the line issupplied from a weak
system (low short-circuit capacity).
A shunt reactor of sufficient size must be permanently connectedto the line to limit
fundamental-frequency temporary over voltages toabout 1.5 pu for a duration of less than 1
second.
Additional shunt reactors required to maintain normal voltageunder light-load conditions may
be connected to the EHV bus. 50 MVAR and 80 MVAR are the typical reactor size used in
400 kV and higher system. However during heavy loading conditions, some of the reactors
may have tobe disconnected.
Shunt capacitors are used to compensate for the heavy loading conditions.Switching of
capacitor banks provides a convenient means ofcontrolling transmission system voltages.
Series capacitors are connected in series with the lineconductors to compensate for the
inductive reactance of the line.
STATCOMS, SVC etc are used in MV and EHV range. D-STATCOM, automatic power
factor correction (APFC) units are used in 11 kV and LT system. An APFC unit consists of a
number of capacitors that are switched ‗ON‘ or ‗OFF‘ by means of contactors. These
contactors are controlled by a regulator that measures power factor in an electrical network.
Depending on the load and power factor of the network, the power factor controller will
switch the necessary blocks of capacitors in steps to make sure the power factor stays above a
selected value. The optimum rating and optimum locations for given network and the cost
benefit analysis can be done in CPRI.[Annexure-1]
The most effective method of reactive power management in distribution system is by power
factor improvement by using power capacitor.
kVAr requirement calculation need measurement of actual power factor, desired power factor
and load in kW. The Table 3 gives multiplication factor to obtain required kVAr. If average
power factor is 0.5 and is to be improved to 0.94 then 180.7 kVAr capacitor is required for
100 kW load. Similarly for 500 kW load, 408.5 kVAr capacitor is required to improve the
power factor to 0.98 from 0.7.
0.9 0.92 0.94 0.96 0.98 0.99
0.4 1.807 1.865 1.928 2.000 2.088 2.149
0.45 1.500 1.559 1.622 1.693 1.781 1.842
0.5 1.248 1.306 1.369 1.440 1.529 1.590
0.55 1.034 1.092 1.156 1.227 1.315 1.376
0.6 0.849 0.907 0.970 1.042 1.130 1.191
0.65 0.685 0.743 0.806 0.877 0.966 1.027
CPRI-Training Notes
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0.7 0.536 0.594 0.657 0.729 0.817 0.878
0.75 0.398 0.456 0.519 0.590 0.679 0.739
0.8 0.266 0.324 0.387 0.458 0.547 0.608
0.85 0.135 0.194 0.257 0.328 0.417 0.477
0.9 0.000 0.058 0.121 0.193 0.281 0.342
Table 3: Multiplication factor for kVAR requirement
After calculation of kVAr requirement, the type of capacitor is to be selected. It will be
standard duty, heavy duty etc depending upon operating life, number of operation per year
etc.
Next calculations are required to check whether this capacitor value will result in resonance
which can damage electrical equipment including capacitors. Suitable filter reactor will be
required to avoid resonance.
Based on the ratio of the rating of incoming transformer and capacitor kVAr,fixed type
capacitor or automatic power factor correction panel is selected.
Excellent test facilities have been created in CPRI for testing LV APFC panels as per IEC
61921 and IEC 61439.
The awareness about reactive power management has resulted in many states coming out
with pricing scheme for reactive power. This is listed in Appendix-A.
Appendix-A
Reactive Power Pricing scheme in different states
CPRI-Training Notes
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Annexure-1
Optimum Capacitor banks for distribution feeder
R.A.Deshpande
Joint Director, DSD, CPRI
Abstract: This paper examines use of capacitor bank in a realistic distribution system. The
distribution system can be distinctly classified as urban, industrial and rural. The length of
feeders, type of loads and load-time curve varies widely for each of these types. The
efficiency of the feeder can be improved by use of shunt capacitors. However for already
existing distribution feeders whose length runs into tens of kilometers and also where ratio of
LT line length to HV line length is higher, the usage of capacitor bank can be very
complicated. Though it can be said very easily that I2R losses and voltage profile along the
feeder can be improved by using capacitor bank, optimum selection of capacitor bank in
terms of (i) size vis-a vis cost, (ii) number of capacitor banks and their location for reducing
energy losses on one hand and maintenance and cost on the other hand, (iii) capacitance
value and permissible rise of voltage during different load conditions (iv) limiting the
increase in short-circuit current in case of fault can be very complicated. A typical rural
feeder is considered and analysis is presented in this paper to demonstrate possibility of most
optimum solution.
Introduction
Electrical energy has become integral part of the economic development of human society.
Power is indispensable resource in today‘s high technology driven world and the power
industry is one of the main pillars of nation‘s overall development. Transmission lines and
distributions lines carrying the power are like blood vessel carrying oxygen in the human
body. However rapid growth of load centers, demands of agriculturist, transformation of
cities into big cities and metros require large power to flow long distance from widely
dispersed generating sources.
Due to nature of load i.e having less than unity power factor, requires significant amount of
reactive power (VAR) in addition to consumer‘s active power (W) requirement. If this
reactive power has to flow from the same generating sources, the transmission lines and
distribution lines, the overall reactive power flow would be much higher because of the
inductance of transmission and distribution line. This results into increase in I2R losses and
voltage reduction along the line, maximum reduction being at tail end. The shunt capacitors
act as source of reactive power. They increase the voltage at the point of connection. To
summarise, the shunt capacitors reduces the losses, improves the voltage profile, help in
reduction in conductor/transformer/protective equipment sizing. The benefits are very clear.
The task of finding out the optimum solution is tedious as many permutation and
combinations are possible.
I Distribution network under study
A typical distribution feeder as shown in Fig.1 is considered for study purpose. This is rural
type of feeder with most of the load being agricultural pump motors. The substation
CPRI-Training Notes
46
transformer from rating which this feeder emanates is 66/11 kV, 10 MVA. The total length of
11 kV feeders is about 17.5 km from one end to other end with many tap feeders along the
line. There are 108 numbers of 11 kV/433 V distribution transformers (DT) of various rating
like 25 kVA, 63 kVA and 100 kVA. The secondary load is lumped and considered at the
terminal of the secondary of the concerned DT. The value of load is 15 days average in a
particular month. The impedance value of secondary line is added in the load value and not
separately simulated. Hence there will be 108 numbers of loads. Each of these loads is three
phase balanced load and specified in terms of kW and power factor.
Fig 1. The 11 kV rural distribution feeder
The load flow analysis using Voltage Drop calculation method based on current iterations is
used as the solution algorithm. Table 1 shows the summary of load flow results. No capacitor
compensation is considered initially. It was also observed that at one particular node the
voltage is as low as 0.74 pu and at one other voltage is 0.92 pu. The voltages at all other
nodes are within 95 to 100%. There is no overvoltage on any section.
Table1. Load Flow result
kW kVAR kVA PF(%)
Sources (Swing) 711.25 343.11 789.68 90.07
Generators 0 0 0 0
Total Generation 711.25 343.11 789.68 90.07
Load
679.97 320.42 751.68 90.46
Shunt capacitors 0 0 0 0
Total Loads 679.89 320.13 751.49 90.47
Line Capacitance 0 24.68 24.68 0
Total Shunt Capacitance 0 24.68 24.68 0
CPRI-Training Notes
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Line Losses 11.08 38.79 40.34 27.46
Cable Losses 0 0 0 0
Transformer
Losses 20.27 8.86 22.13 91.63
Total Losses 31.35 47.66 57.05 54.96
II Different Cases, Results and Discussions
For this feeder, objective will be to reduce the losses to the extent possible, improve the overall
power factor of the system and improve the voltage at the two nodes which are below
permissible limits,. The constraints will be to use minimum number of capacitor banks, to use
minimum rating of capacitor rating. Very importantly voltage at point should not increase
beyond the permissible higher limit of 105%. Based on the market conditions, the minimum
capacitor bank rating selected is 3 kVAr, maximum being 54 kVAr. The increment in
capacitor bank is 3 kVAr. The power improvement was kept as 0.98. The calculations gave
15 possible locations which are as shown in green mark in Fig.2 in the same network diagram.
The value of capacitor bank required is 9 kVAr for 13 locations and 18 kVAr at two DT
locations.
Fig.2 The same network with optimum location of capacitor bank
The load flow study was repeated with these values of capacitor. The results are tabulated in
Table.2. The losses are reduced by 4.6 % from earlier 31.35 kW to 29.91 kW. The under
voltage at the nodes is slightly improved to 0.7443 pu and 0.9375 pu respectively.
Table 2. Load Flow result after placement of capacitors
kW kVAR kVA PF (%)
CPRI-Training Notes
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Sources (Swing)
709.86 190.53 734.98 96.58
Generators
0 0 0 0
Total Generation 709.86 190.53 734.98 96.58
Load
679.97 320.42 751.68 90.46
Shunt capacitors
0 145.31 145.31 0
Total Loads 679.94 175.08 702.12 96.84
Line Capacitance
0 25.4 25.4 0
Total Shunt Capacitance 0 25.4 25.4 0
Line Losses
9.38 32.83 34.14 27.47
Transformer Losses
20.54 8.02 22.04 93.15
Total Losses 29.91 40.84 50.63 59.09
The savings in the loss reduction is of the order of Rs.50457 per year while the cost of
installation of 13 x 9 + 2x 18 kVAr capacitor bank is Rs.28837.Due to maintenance point of
view suppose the number of capacitor location are to limited to say maximum of 5, then this
calculation gives two location with 135 kVAr capacitor bank at one node and 9 kVAr capacitor
bank at other node. Here the number of locations has been optimised , remaining very close
to main objective. The total loss in this case is 30.27 kW.
It is also possible to have distance of capacitor bank from substation as constraint. Say as a
standard practice the minimum distance of capacitor bank locations from substation is to be
maintained. Solutions for this type of constraint can be also found. With minimum distance of
5000 meters as constraint, study gave 13 locations within 500 meters distance from substation.
It also gave the capacitor bank size, in this case it is 9 kVAr incidentally at all the location. The
total losses are 30.28 kW.
III Different load conditions
In case the peak load is very much higher than normal load, the study is more useful. It gives
optimum location of fixed capacitors and optimum location of switched capacitors along with
rating of capacitor bank ratings. First normal load is considered and rating and location of
capacitor bank is determined. Then considering the peak load, the rating and location where
still the fixed capacitor can be used without violating the upper voltage limit is found. Then the
switched capacitor which needs to be switched during normal load condition location and their
rating is obtained. It is attempted to keep the rating of switched capacitor bank as low as
possible.
Peak load was taken as 170 % the normal load and the study was repeated. 36 locations with 9
kVAr rating capacitor bank is required. 14 locations are to be provided with fixed capacitors
CPRI-Training Notes
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and 22 locations are to be provided with switched capacitor banks. It was also ensured that
even when these switched capacitor banks are not switched off during normal load flow, the
voltage rise will not be more than 105 %.
IV Conclusions
The reactive power compensation is very important to strengthen the weaker distribution
system network. It is most economical means of increasing power transfer. The key objective
of reduction of power losses, increase of power flow capacity and improvement in voltage
profile can be achieved with use of shunt capacitor. Coupled with study for optimum solution
with different constraint can give best economical choice.
References
[1] J. V. Schmill, "Optimum Size and Location of Shunt Capacitors on Distribution Feeders,"
IEEE Transactions on Power Apparatus and Systems, vol. 84, pp. 825-832, September 1965.
[2] H. Dura "Optimum Number Size of Shunt Capacitors in Radial Distribution Feeders: A
Dynamic Programming Approach", IEEE Trans. Power Apparatus and Systems, Vol. 87, pp.
1769-1774, Sep 1968.
[3] J.J. Grainger and S. Civanlar, ―Volt/var control on Distribution systems with lateral
branches using shunt capacitors as Voltage regulators-part I, II and III,‖ IEEE Trans. Power
Apparatus and systems, vol. 104, No. 11, pp. 3278-3297, Nov. 1985.
[4] M. E Baran and F. F. Wu, ―Optimal Sizing of Capacitors Placed on a Radial Distribution
System‖, IEEE Trans. Power Delivery, vol. No.1, pp. 1105-1117, Jan. 1989.
[5] M. E. Baran and F. F. Wu, ―Optimal Capacitor Placement on radial distribution system,‖
IEEE Trans. Power Delivery, vol. 4, No.1, pp. 725734, Jan. 1989.
[6] MasoudAliakbar GOLKAR, ―A Novel Method for Load Flow Analysis of Unbalanced
Three-Phase Radial Distribution Networks,‖ Turk J ElecEngin, VOL.15, NO.3 2007,
CPRI-Training Notes
50
REACTIVE POWER COMPENSATION- POWER FACTOR IMPROVEMENT
By T.BhavaniShanker, Engineering Officer Grade4, DCCD, CPRI
1.0 INTRODUCTION
This section deals with some of the basic concepts of installation of shunt capacitors for power factor improvement. Phase displacement between voltage and current in industrial loads, need for power factor correction, practical considerations of installation of capacitors, etc., are explained.
1.1POWER IN ALTERNATING CURRENT – ACTIVE AND REACTIVE POWER
In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as real power (also referred to as active power). That portion of power flow due to stored energy that returns to the source in each cycle is known as reactive power.
The relationship between real power, reactive power and apparent power can be expressed by power triangle(refer to Figure 1). Using the Pythagorean Theorem, the relationship among real, reactive and apparent power is:
(Apparent power, kVA )2 = (Real power, kW)2 + (Reactive power, kvar)2
Figure 1: Power triangle: The components of AC power
IMPEDANCE AND REACTANCE
Circuits in which current is proportional to voltage are called linear circuits. The ratio of voltage to current in a resistor is its resistance (R). Resistance does not depend on frequency, and in resistors V and I are in phase. However, in majority of the practical circuits the loads are not pure resistors and the ratio of voltage to current does depend on
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frequency and in general there is a phase difference. Impedance (Z) is the general name given to the ratio of voltage to current. Resistance is a special case of impedance. Another special case is that in which the voltage and current are out of phase by 90°: this is an important case because when this happens, no power is lost in the circuit. In this case where the voltage and current are out of phase by 90°, the ratio of voltage to current is called the reactance (X).
Capacitive reactance XC is the ratio of the magnitude of the voltage to magnitude of the
current in a capacitor.
Capacitive reactance,Xc = 1/ωC = 1/2πfC
There will be a phase difference between voltage and current: Voltage is 90° behind the
current as shown in Figure 2. In other words, capacitor current leads the voltage by 90°.
Capacitor reactance (the ratio of voltage to current) decreases with frequency.
Figure 2: Capacitor in AC circuit
Inductive reactance XL is the ratio of the magnitudes of the voltage and current.
Inductive reactance, XL = ωL = 2πf L
There will be a phase difference between voltage and current. Voltage across the ideal
inductor is 90° ahead of the current as shown in Figure 3. In other words, inductive current
lags the voltage by 90°. Inductive reactance is frequency dependent and increases with
frequency.
Figure 3: Inductance in an AC circuit
Impedance is the general term for the ratio of voltage to current. The table below
summarizes the impedance of the different components. The same information is given
graphically in Figure 4.
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Figure 4: Dependency of Impedance on frequency
RLC SERIES COMBINATIONS
Consider a circuit having resistors, capacitors, and inductors connected in series in one
circuit. If all three components are present, the circuit is known as an RLC circuit (or LRC)
as shown in Figure 5. If only two components are present, it's either an RC circuit, an RL
circuit, or an LC circuit.
Figure 5: RLC Series circuit
The overall resistance to the flow of current in an RLC circuit is known as the impedance,
symbolized by Z. The impedance is found by combining the resistance, the capacitive
reactance, and the inductive reactance. Unlike a simple series circuit with resistors, however,
where the resistances are directly added, in an RLC circuit the resistance and reactance are
added as vectors. This is because of the phase relationships. In a circuit with just a resistor,
voltage and current are in phase. With only a capacitor, current is 90° ahead of the voltage,
and with just an inductor the reverse is true, the voltage leads the current by 90°.
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Series impedance (Zseries): the ratio of the voltage to current in an RLC series circuit.
Reactances and resistances add according to Pythagoras' law (Refer to Figure 6) are related
by the following formulae:
Zseries2 = R2 + Xtotal
2
= R2 + (XL - XC)2.
Figure 6: Phasor diagram
Inductive and capacitive phasors are 180° out of phase, so their reactances tend to cancel. The power dissipated in an RLC circuit is given by:
Note that all of this power is lost in the resistor; the capacitor and inductor alternately store
energy in electric and magnetic fields and then give that energy back to the circuit.
Setting the inductance term to zero gives back the equations for RC circuits, though note that phase is negative, meaning that voltage lags the current. Similarly, removing the capacitance terms gives the expressions that apply to RL circuits.
Figure 7 shows the special case where the frequency is such that VL = VC.
Figure 7: Series resonance
Because vL(t) and vC are 180° out of phase, this means that vL(t) = - vC(t), so the two reactive voltages cancel out, and the series voltage is just equal to that across the resistor. This case is called series resonance.
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1.2 ENERGY STORED IN CAPACITANCE AND INDUCTANCE
One of the main differences between resistors, capacitors, and inductors in AC circuits is in
what happens with the electrical energy. With resistors, power is simply dissipated as heat. In
a capacitor, no energy is lost because the capacitor alternately stores charge and then gives it
back again. In this case, energy is stored in the electric field between the capacitor plates.
The amount of energy stored in a capacitor is given by:
Energy Stored in Capacitor:Ec = ½ CV2
There is also no energy lost in an inductor, because energy is alternately stored in the
magnetic field and then given back to the circuit. The energy stored in an inductor is:
Energy Stored in inductor: 𝑬𝑳= 𝟏
𝟐(𝑳𝑰𝟐)
POWER RELATIONSHIPS IN AC CIRCUITS
AC power flow has the three components:
Real power(Active power)(P), measured in watts (W);
Apparent power (S), measured in volt-amperes (VA); and
Reactive power (Q), measured in reactive volt-amperes (var)
For power factor of cosΦ as shown, by definition Active power (kW) taken by the load = EI cosΦ 10-3
Reactive power (kvar) taken by the load = EI sinΦ 10-3
Apparent power (kVA) taken by the load = EI × 10-3
Power factor load = Active power (kW) / Apparent power (kVA) = cosΦ
Active power (kW) = √kVA2 – kvar2 = kVA cosΦ
Reactive power (kvar) = √ kVA2 – kW2 = kVA sinΦ = kW tanΦ
Apparent power (kVA) = √ kW2 + kvar2 = kW/cosΦ
1.3 POWER-FACTOR CORRECTION
Most ac electric machines draw from the supply apparent power in terms of kilovolt-amperes (kVA) which is in excess of the useful power, measured in kilowatts (kW), required by the machine. The ratio of these quantities (kW/kVA ) is called the power factor cosΦ and is dependent on the type of machine in use.
𝑷𝒐𝒘𝒆𝒓 𝑭𝒂𝒄𝒕𝒐𝒓 (𝐜𝐨𝐬∅) =𝑼𝒔𝒆𝒇𝒖𝒍 𝒑𝒐𝒘𝒆𝒓 (𝒌𝑾)
𝑨𝒑𝒑𝒂𝒓𝒆𝒏𝒕 𝑷𝒐𝒘𝒆𝒓 (𝒌𝑽𝑨)
A large proportion of the electric machinery used in industry has an inherently low pf, which means that the supply authorities have to generate much more current than is theoretically
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required. In addition, the transformers and cables have to carry this high current. When the overall pf of a generating station’s load is low, the system is inefficient and the cost of electricity correspondingly high. To overcome this, and at the same time ensure that the generators and cables are not loaded with the wattless current, the supply authorities often impose penalties for low pf.
Some of the machinery or equipment with low pf are listed below:
1. Induction motors of all types 2. Power thyristor installations 3. Welding machines 4. Electric arc and induction furnaces 5. Choke coils and induction furnaces 6. Neon signs and fluorescent lighting.
The method employed to improve the pf involves introducing reactive (kvar) into the system in phase apposition to the wattless or reactive current. This is achieved either with rotary machines (synchronous condenser) or static capacitors.
The apparent power (kVA) in a.c. circuit can be resolved into two components, the in-phase component which supplies the useful power (kW), and the wattless component (kvar) which does no useful work. The phasor sum of the two is the kVA drawn from the supply. The cosine of the phase angle between the kVA and the kW represents the power factor of the load. This is shown by the phasor diagram in Figure 9 (a).
To improve the power factor, equipment drawing kvar of approximately the same magnitude as the load kvar, but in phase opposition (leading), is connected in parallel with the load. The resultant kVA is now smaller and the new power factor (cosine Φ2) is increased (Figures 9(a) and (b)). Cosine Φ2 is controlled by the magnitude of the kvar added. Thus any desired power factor can be obtained by varying the leading kvar. A typical arrangement of shunt capacitor connected in parallel with a load is shown in Figure 10.
Figure 9(a): Phasor diagram of a plant operating at a lagging power factor
Figure 9(b): Power factor correction by adding leading kvar
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Figure 10: Capacitor connected in parallel with load
CALCULATION OF CAPACITOR kvar FOR PF CORRECTION
Capacitor kvar required to correct power factor from cosΦ1 to cosΦ2 is given by the formula as depicted in Figure 11.
Capacitor (kvar) = (kvar1 – kvar 2)
= kW(tanΦ1 – tanΦ2)
Figure 11: Phasor diagram for finding the size of capacitor
required to correct to a given power factor.
This value of capacitor kvar can be determined either by drawing the phasor diagram to the scale or by calculation using the values from trigonometric tables.
As example is illustrated below:
Given, 100 kW load to be improved from 0.77 to 0.95.
Capacitor (kvar) = kW (tanΦ1 – tanΦ2)
= 100 ( 0.5) = 50 kvar
That means, for improving the pf from 0.77 to 0.95 for a load of 100 kW, capacitor of 50 kvar to be connected.
1.4 DETERMINATION OF LOAD CONDITIONS
The first step in designing any practical power factor correction scheme must be to obtain accurate details of the load conditions with values of kW, kVA, Power factor at light, average and full load, together with type and details of load and presence or absence of harmonics. This may be achieved by conducting a system study at the proposed site of installation of capacitors with the help of a suitable power analyzer for a period of minimum 24 hours. From this information, conditions of the existing power factor can be calculated. Such study also helps to assess power quality particularly with reference to harmonics, type of loads, loading patterns, etc.
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1.5 RATED VOLTAGE OF CAPACITOR:
As IEC 60871 and IEC 13925, HV capacitors can take only rated voltage continuously. Also, capacitor design shall accommodate 10 % over voltage for a period of 12 hours in a day. For example, for a 11 kV system, if the voltage variation is 10 %, capacitors shall be rated to 12.1 kV. This will ensure proper performance from capacitors.
When reactors are used in series with capacitors, it gives voltage rise at capacitor terminals. For example, a 6 % reactor will increase the capacitor voltage by approximately 6 %. Therefore, capacitor rated voltage should be corrected by raising the rated voltage further to that extent.
INCREASE IN BUS VOLTAGE DUE TO CAPACITORS
Capacitor gives boost to the voltage where they are connected to a circuit, on account of reduction in line current and resultant drop in I (line current) x Z (system impedance). In most of the cases, rise in voltage is normally limited to 2 to 3 %.
For example, 1 MVAr capacitor is connected to a 5 MVA incoming transformer with 6 % impedance, then voltage rise can be calculated as
% over voltage = % Impedance x (capacitor MVAr / Transformer MVA)
= 6 x (1/5)
= 1.2
When large capacitors are connected to system through dedicated transformers, over voltage
will be large and shall be taken into account while deciding the rated voltage of capacitor
bank.
1.6 SIZING OF CAPACITOR BANK
Capacitor output (kvar) is proportional to the square of the voltage and frequency. For example, consider installation of 1MVAr capacitor to a 11 kV system. As explained earlier, rated voltage of the capacitor should be 12.1 kV (=1.1x 11 kV). For this increased voltage, corrected output rating of the capacitor will be
1 MVAr x (12.1 x 12.1)/(11 x 11) = 1.21 MVAr
When capacitor bank is provided with series reactor, say 6%, the rating of capacitor needs to be corrected for loss in series reactor. For the same requirement of 1 MVAr at 11 kV, the voltage is chosen as
Rated voltage = 11 x 1.1 / (1- 0.06) kV
= 12.87 kV
Capacitance impedance at 11 kV bus,
Xc = (11 x 11)/ 1 = 121 ohms
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Corrected capacitor impedance
X’c = Xc / (1- 0.06) = 121 / 0.94 = 128.72 Ohms
Therefore,
Capacitor Output = (kV x kV )/ X’c = 12.87 x 12.87 / 128.72 = 1.28 MVAr
Series Reactor impedance = 0.06 x X’c = 7.73 Ohms
Therefore, 1.28 MVAr, 12,87 kV capacitor bank with 6 % series reactor will give 1 MVAr at 11 kV bus.
1.7 LOCATIONS FOR INSTALLATION OF CAPACITORS
Normally capacitors can be installed at the distribution boards but if it is required to reduce loading on feeders, or if the metering is at high tension and it is required to install low voltage capacitors, then it is necessary for sub-circuit tests to be made to determine the point of connections of the capacitors. This is especially important in average power factor installations. These clip-on tests are usually made using clip-on ammeters, kW meters and kvar meters.
For average industrial consumers, the capacitors are normally connected to the low voltage side of the transformers irrespective of whether the supply is taken at high voltage or low voltage. This relieves the transformer of unnecessary load and also helps compensate for the transformers magnetizing current.
1.8 ECONOMIC CONSIDERATIONS
While considering the economics for power factor (pf) correction, it is most important to remember that any pf improving plant, in general, compensate for losses and reduce the current loadings on supply equipment, i.e., cables, transformers, switchgears, generating plant, etc.
The rating of the capacitors required to improve pf depends largely on the tarrif. Savings obtained from installing pf correction equipment depends on the tariff structure, like , kVA-hours, kvar-hours, maximum demand kVA, all of which quantities are reduced by installing pf correction capacitors.
The points to be considered in any installation are:
1. Reliability of the equipment to be installed
2. Probable life
3. Capital cost
4. Maintenance cost
5. Running cost
6. Space required and ease of installation
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The power capacitors owing to their low dielectric losses, compact size, simplicity and high efficiency, are considered almost universally for pf correction. It is usually found that the expenses of correcting a low pf by means of capacitors is less than the savings effected in the first 18 months: subsequent annual savings are thereafter clear profit.
1.9 PROTECTION OF HV CAPACITOR BANKS
A broad summary of the classes of protection employed for HV capacitor banks is given in Table 1. For larger capacitor banks all three classes are employed. These classes of protection are complementary to one another and are not alternatives.
Table 2: Summary of Classes of High voltage capacitor protection
Class of Protection
Method Location Type Comments
prrimary Fuse link External at unit terminal
HRC
For delta connected or single –phase banks only
External at unit terminal
Expulsion
For star –connected banks only
Internal-buried in element
TC wire Inside each unit
Secondary Relay Energized from CTs between star pointed interconnection of bank
or
Out-of-balance current
or
To provide alarm and trip facilities in conjunction with capacitor control switch
Relay Energized from CTs across capacitor phases or between star point and earth
Out-of-balance current
To provide alarm and trip facilities in conjunction with capacitor control switch
Line Relays Main incoming supply to complete bank
O/C and E/L protection
To protect system and complete bank and connections from short circuits
Relays Main incoming Close current To prevent excessive
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supply to complete bank
o/load protection
current o/loading especially from harmonics
Relays Main incoming supply to complete bank
Overvoltage protection
To prevent over voltages including effects of voltage wave distortion
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POWER CAPACITORS
2.0 INTRODUCTION
In spite of the phenomenal growth of power generation in the country during the last two decades, the demand has always outgrown the supply. To meet this increasing demand, continued efforts are needed not only for more generation but also for conservation of generated energy and improvement in system design. Transmission and distribution losses have risen considerably due to various reasons. One of the measures to reduce the system losses is to connect capacitors across individual inductive devices and / or at various strategic points of the system. Application of power capacitors is increasing rapidly in the Industries (both heavy and small scale), which use motors, transformers, electric furnaces, etc., in order to compensate for the inductive loads and consequently improve the power factor close to unity and also improve the voltage profile.
Power Capacitor Industry has seen a phenomenal growth during past 10 to 15 years. Capacitors of unit rating up to 1000 kvar 15 kV AC are being manufactured. With the availability of high dielectric strength and low loss materials like polypropylene (PP) film and improved processing techniques, high voltage capacitors with very low dielectric losses are
being manufactured. The design stress is in the range of 60 V/m to 80 V/m. The motive behind these phenomenal changes is to achieve compactness, minimum dielectric loss, low cost and importantly, improved reliability.
Although the performance of power Capacitors in service is generally satisfactory, several instances of premature failures of power capacitors have been reported by utilities. Capacitor failures have been experienced during laboratory testing also. While most of the Capacitor failures are generally attributed to the poor material quality, there are also some reports of spurious capacitors in operation. Capacitor failures have been observed due to selection of wrong type of capacitors and presence of system disturbances like harmonics, transients etc.
This article covers some of the details like scenario of capacitor technology, construction and material details of capacitors, importance of testing, a general sequence of testing for HT shunt capacitors, maintenance of capacitor banks and facilities CPRI for research, testing and certification of power capacitors.
2.1 INTERNATIONAL SCENARIO OF CAPACITOR TECHNOLOGY
Power capacitor industry has seen a phenomenal growth during the past 10 to 15 years. New developments in materials, design, processing, construction etc., have taken place, which aim towards higher unit rating and compact size. These changes are summarized in Table 1 along with
their effect on capacitor dissipation factor (tan ) and design stress.
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With the availability of high insulation strength and low loss dielectric materials and improved processing techniques, high voltage capacitors with very low insulation losses are being manufactured as indicated in Table 1. PP film impregnated with suitable synthetic oil has become the most commonly employed insulation for power capacitors, with the design stress as high as 80
V/m. Due to these developments, the power rating of shunt capacitors has reached as high as 1000 kvar per unit.
Table 1: Evolution of capacitor technology
Capacitor material
and construction
LT capacitor HV capacitor
Present status of technology
Year tan
%
Stress
V/m
Year tan
%
Stress
V/m
Paper- Al foil Polychloro-biphenyl (PCB) impregnant
1940 0.3 18 1940 0.3 18 Not in use due to toxic nature of PCB
PP-Paper-Al foil
PCB impregnant
1972 0.3 18 1965 0.05 49 Not in use due to toxic nature of PCB
PP-Paper-Al foil
Synthetic impregnant
1977 0.05 55 Finds application in CVTs and for some special application
Metallised PP film 1977 0.02 45 Widely used for 400 V range
Metallised PP film, Synthetic impregnant
1977 0.02 50 Used in 650 V range
All PP film(Hazy)-Al foil synthetic impregnant
1979 0.02 70 Widely used
All PP film (Hazy)-Embossed Al foil, Synthetic impregnant
1980 0.02 70 Not widely used
All PP film (Hazy)-Folded edge Al foil Synthetic impregnant
1990 0.02 75-80 Widely used
All PP film (Hazy)- Laser cut Al foil, Synthetic impregnant
1995 0.02 75 Under trial
The basic raw materials presently being employed for HV capacitors are listed below:
(1) Solid insulation: Bi-axially oriented polypropylene film (BOPP) is the most commonly employed insulation for HV capacitor. To facilitate the process of impregnation, the
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surface of PP film is made hazy by corona treatment. Wide application of PP film in HV capacitors is mainly due to its good electrical and mechanical properties like:
High electric strength of the order of 250 –300 V/m ac Low dissipation factor less than 0.0002 Thermally and electrically compatible with insulating oils employed as capacitor
impregnants. Good machinability
Electrical grade PP film is generally available in thickness in the range of 8, 10, 12, 15 and 18 m. The requirement of PP film for power capacitor application is specified in IEC 674 (equivalent Indian Standard is IS 11298 (Part 3/Sec 1): 1991 as given in Table 2.
Table 2: Requirements of PP film for HV capacitor application
Sl. No.
Property Clause Ref. of IS 11298 (part 2)-
1987
Requirements Tolerance
1 Thickness in m
(Preferred thickness)
4.5 8,9,10,11,12,14,15.2,16.5,18 &20
6%
2 Space factor for hazy film (%)
4.5
10 2%
3 Width in mm 8 Preferred width not specified
1%
4 Density (gm/cm2) 6.1.2 0.905 0.005 %
5 Tensile strength at break (N/mm2)
12 140 Minimum
Specified
6 Elongation at break (%)
Both along machine direction (MD) and
cross machine direction (CMD)
12 40 Minimum
Specified
7 Heat shrinkage (%)
i) along MD
ii) along CMD
24
4
2
Average
8 DC Dielectric strength
(volts/m)
19.2 6m: 250
8-11m: 300
>12m: 450
9 Volume resistivity 16 1x1016 Maximum
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( cm) at 2720 C and
605%
specified value
10 Dissipation factor at 270C, 48-52 Hz and
500volts ac
17 2 x 10-4 Maximum specified value
11 Dielectric constant at 270 C, 48-52 Hz
17 2.2 0.05
12 Electrical weak spots (counts/m2)
20 6m: 6
8-9m: 4
10-11m: 3
12 m: 2
>14m: 1
Maximum specified
Value
(2) Capacitor impregnant: The most commonly employed capacitor impregnants are Phenyl Xylyl Ethane (PXE) (Dielektrol III) DOP (Dielektrol II) Isopropyl Biphenyl (IPB) Benzyl Neocaprate (Faradol) Di Isopropyl Napthalene Jarylec (blend of benzyltoluene and di benzyltoluene)
The important properties, which decide the selection of capacitor impregnant are, dielectric constant, breakdown strength, viscosity, aromatic content, flash point and pour point. Compatibility of the impregnant with PP film also plays an important role, particularly with respect to swelling of PP film. The impregnants should be biodegradable and non-toxic, unlike PCBs (Polychloro-biphenyl). The characteristics of capacitor impregnant shall comply with the requirement of Clause 4.2 of IS 13067:1991.
The capacitor units used in the present study are generally impregnated with PXE. The key properties of PXE are listed below:
Property Value
Dielectric constant, 25 C : 2.5
Breakdown voltage, kV/25 mm gap
: 80
Flash point : 148C
Pour point : -48C
Viscosity, 38C : 6.1 cs
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PP film swelling, % : 12
Aromatic content, % : 75
2.2 CONSTRUCTION OF HV CAPACITORS
High Voltage power capacitors consist of a number of basic elements, which are constructed by winding two layers of Aluminium foil interleaved by two or three layers of PP film. HV capacitors are generally constructed with extended foil arrangement where Aluminium foils extend beyond the edge of PP film. After completion of winding process, the elements are assembled into parallel group consisting of generally 12 elements. Such stacks are connected in series to achieve
the required voltage and output. After assembling, discharge devices and internal
fuses (for internally fused capacitors) are provided. Inter element connections are generally made by soldering a metal strip on the extended Aluminium foil. A mild steel or stainless steel lid, drilled with two holes to allow impregnation, is then mounted on the capacitor elements pack. Connection leads are brought out to bushings on the lid. This assembly of capacitor elements is fitted into a mild steel or stainless steel case and the lid is welded in position. Once assembled, the capacitor undergoes a vacuum drying process and impregnation and on completion of this process the holes in the lid are sealed. Winding of capacitor element and impregnation process are usually computerized for accurate control.
Construction details of HV capacitors, from element to finished product, are shown in Figure 1.
Figure 1: Internal construction of HV capacitor - Schematic
Typical output ratings (kvar) of HV capacitors are, 181, 200, 220, 350, 400, 770, 1000, etc. and Typical voltage rating of HV capacitors are, 3.3 kV, 6.6 kV, 7.3 kV, 12 kV, 18 kV.
Most generally accepted parameters for construction of a HV capacitor are given below with typical dimensions of PP film and Aluminium foil for a rating of 200 kvar, 7.3 kV.
Number of series group / unit : 4
Source: M/s. ABB Ltd.
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Number of parallel elements / Series. group : 12
Width of PP film : 320 mm
Active width of Al. Foil : 320 mm
Edge folding : 5 mm
End folding : 20 mm
Active width of foil : 296 mm
Exposed foil : 6 mm
Discharge device : Internally fitted
Active length of the element : 14 meters
Thickness of Al foil : 6 m
Thickness of PP film : 10 m
Number of PP layers : 3 numbers
Element Connection : Soldered type
Internal fuses : Present in internal fuse type capacitors
Installation of Capacitor Banks
A typical layout of a 1.5 x 3 Mvar, 13.8 kV shunt capacitor bank along with the adjacent distribution load are shown in Figure 2 The capacitor banks are designed to switch on and off automatically based on power factor, vars, and /or voltage.
Figure 2 Typical drawing showing a 13.8 kV, 4.5 Mvar and adjacent distribution loads.
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A view of MV capacitors installed indoor in a APFC panel is shown in Figure 3. A view of HV capacitor bank is shown in Figure 4.
Figure 3. Capacitor Bank Installed (APFC Panel)
in an Industrial site.
Figure 4. A View of HV Capacitor Bank
3.0 SCENARIO OF INDIAN CAPACITOR INDUSTRY
The effective load power factor in our transmission and distribution system is 0.8 or below, whereas world-wide practice is to compensate the reactive loads to an extent that the power system operates at a power factor of the order 0.98.
One of the effective remedies to overcome this problem is to improve the load power factor by installing shunt capacitors. The responsibility of installation of capacitors lies with State Electricity Boards (SEB) and power utilities. As per one of the estimates of POWERGRID, there is a shortage of over 10,000 MVAR [2].
Seeing the huge quantum of backlog, Central Electricity Authority (CEA), New Delhi, has made it compulsory to install shunt capacitors at strategic points. CEA has instructed SEBs to expedite capacitor installation program. Very encouraging results were brought out by an indicative cost benefit analysis, which states that the entire cost of installation of capacitors is recovered within a brief period of 12-13 months by way of savings in T&D loss alone. It is heartening to note that, some of the SEBs are taking necessary steps for installation of shunt capacitors, including Karnataka Power Transmission Corporation Ltd (KPTCL).
Thus, application of shunt power capacitors is increasing rapidly for reactive compensation to improve power factor and the voltage profile. The major utilities of shunt power capacitors in the country are State Electricity Boards, Indian Railways, NTPC, PGCIL, BSES, BEST, Steel Industry, Textile industry, etc.
Presently, there are about 15 major HV capacitor manufacturers in the country. Single phase and three phase capacitors of unit rating 736.64 kvar and 14.82 kV ac are being manufactured
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indigenously. Capacitors of unit rating up to 1000 kvar 14.4 kV AC is the highest unit rating single phase HT capacitor manufactured in India as on July 2009.
The Capacitors Laboratory of CPRI, Bangalore is playing an important role in the growth of Indian Capacitor Industry. The laboratory has established full-fledged facilities for carrying out tests as per National and International specifications. Also, the facilities are being upgraded continuously to meet the requirement of industries and test specifications. In addition to testing, the laboratory is also engaged with applied research work in the field of power capacitors. Some of the research investigations have been carried out in association with the capacitor industry for providing facilities and expertise for enhancing the reliability of power capacitors.
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Energy Accounting and Segregation of Technical & Commercial loss in
Distribution System – Case Studies
R. Sudhir Kumar, Engg. Officer, Distribution Systems Division, CPRI
1.0 INTRODUCTION
Growth of economy is invariably liked to infrastructure and energy plays the most vital role
for a vibrant economy. It‘s a well known fact that the financial health of the utilities is a
matter of grave concern. Out of the total energy generated only about 55 % is billed and 41 %
realized. The present situation is characterized by extremely high technical and commercial
losses, poor quality of supply, tardy record in billing and revenue collection etc.
Transmission and Distribution losses in Indian power Systems are higher than those in
developed countries. The losses in India for different states vary between 21 to 43 % with a
national average of 30 %. Reduction of energy losses in transmission and distributions
system has been a matter of great importance to electric power utilities in India.
Losses in general can be identified in Distribution system as 1) Technical losses and 2)
Commercial losses. There are various determinants for high T&D loss and to name a few are
a. Losses in the conductors which can be minimized but cannot be nullified
b. Overloaded feeders.
c. Losses in the Transformers which is a matter of design of the manufacturer and also
loading pattern.
d. Under loaded transformers.
e. Illegal connections such as hooking, tapping, meter tampering, etc
f. False recording or failure to record actual consumption due to faulty meter or improper
meter reading.
Future distribution system will be far more complex then those of today due to fast
urbanization and exponential load growth. This means that the power system generation and
planning task will be more complex. If the system being planned is to be optimal with respect
to construction cost, performance and operating efficiency better planning and analysis are
required. This can be achieved by load flow analysis, short circuit analysis, stability analysis
and power system control. By improving the quality of supply in the distribution system the
overall system performance is improved.
1.1 AT & C LOSSES
The parameters which are of importance to determine the health of a distribution system
(both technical and commercial) are the AT&C losses, the DT failure rates and the average
duration of outages of the 11 kV feeders. The AT&C losses and the DT failures are
invariably linked to each other. For estimation of the AT&C losses, the feeder input to the
town is considered along with the revenue billed and is given by the formula
𝐴𝑇&𝐶 𝐿𝑜𝑠𝑠 = 𝐼 − 𝐵. 𝐸 × 𝐶. 𝐸 ∗ 100 %
𝐶. 𝐸 =𝑅𝑒𝑣𝑒𝑛𝑢𝑒 𝐶𝑜𝑙𝑙𝑒𝑐𝑡𝑒𝑑 𝑖𝑛 𝑅𝑢𝑝𝑒𝑒𝑠
𝐸𝑛𝑒𝑟𝑔𝑦 𝐵𝑖𝑙𝑙𝑒𝑑 𝑖𝑛 𝑅𝑢𝑝𝑒𝑒𝑠
𝐵. 𝐸 =𝐸𝑛𝑒𝑟𝑔𝑦 𝑆𝑜𝑙𝑑
𝐼𝑛𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦
CPRI-Training Notes
70
Where B.E = Billing Efficiency
C.E = Collection Efficiency
The AT&C losses in India vary from a low 8-10 % in AP and TN to a high of 70-80 % for
Jharkhand and Bihar.
2.0 ENERGY ACCOUNTING TECHNIQUES
Energy accounting gives the overall picture of energy availability and its use. Energy audit
would enable to analyse the data in meaningful manner to evolve measures and introduce
checks and balances in the systems to reduce losses and improve technical performance.
Following would be the main objectives of Energy Audit
The review and up gradation of procedure for energy accounting.
Reviewed of technical efficiency of system elements in sub-transmission and distribution
system.
Analysis of techniques for measuring energy receipt, energy billed and revenue
collection.
Reviewed of performance of equipment, meters, DTC etc.
Audit the segregation of the technical and non-technical losses.
Establishment of norms for checking the consumption of various categories of
consumers and overall energy balance.
To achieve consumer satisfaction by reducing tariff with reduction in loss level.
There are mainly two methods of determining the energy losses in T&D system:-
DIRECT METHOD: - In this method losses are found out on the basis of difference of units
sent out and receipt at the end of each element in power system. All though this method helps
in correct determination technical and commercial losses, it is quite expensive to install
energy meters at all location in power system.
IN-DIRECT METHOD: - In this method the losses are determined by simulation of the
network through any software. The advent of powerful computers and good models for
simulations of T&D loss have render this job easy. Some of the software extensively used for
load flow studies and to estimate losses are the ―ETAP‖ and ―CYMDIST‖. The Energy
Profile Module (EPM) of CYMDIST is especially suited for Distribution Systems in which
the energy meter data (Load Survey data) of Distribution Transformers Centers (DTC) can be
directly interfaced with the EPM module to carry out load flow and arrive at energy loss for a
given period of time (E.g. Daily, Monthly and annually)
3.0 CASE STUDIES
3.1 CASE STUDY - 1
ESTIMATIONS OF LOSSES FOR A TYPICAL TOWN-A SIMPLE STUDY
A simple energy accounting study was carried out in a typical town in order to find the
AT&C (Aggregate Technical and Commercial) loss. This town has are four sections and
Three substations feeds this town.
3.1.1. METHODOLOGY USED:
CPRI-Training Notes
71
The Input energy of feeder is collected directly from feeder meters available at Substations
and Output energy required for loss calculation is taken directly from metered energy of
consumers. With the above calculations and assumptions, the total input and total output of
the town scheme is estimated.
Following were the steps used for energy loss calculations
3.1.1.1 Consumer energy billed:
The Consumer energy billed for the months of November and December for this typical town
is evaluated by considering the HT and the LT energy billed which are billed separately.
Table 1 shows the LT energy billed and Table 2 shows the HT energy billed along with the
revenue billed and collected.
3.1.1.2. Input Energy:
There are twenty 11 kV feeders feeding this town scheme, Out of twenty feeders, 15 feeders
are independent i.e. they feed only one section and therefore input energy read directly from
the feeder meters. The other 5 feeders feed more than one section,. Therefor load sharing
calculations us based on kVA and the input energy to the concerned section computed and
shown in Table 3
TABLE 1
LT UNITS (KWH) FOR THE MONTH OF
NOVEMBER AND DECEMBER
Sl.
no
Section
Name November December
1 Section-1 1847000 2299000
2 Section-2 989000 1399000
3 Section-3 1076000 1145000
4 Section-4 1121000 1127000
Total LT units 5033000 5970000
TABLE 2
HT DATA COLLECTED
Section Name Month Metered
energy
Revenue
billed
Revenue
Collected
excluding arrear
Revenue
collected
including arrear
Section-1
November
6406691 24681623 18227851 18227851
Section-2 181487 917168 889226 889226
Section-3 2337956 9955800 8176012 8665459
Section-4 9570 54735 54735 54735
Total 8935704 35609326 27347824 27837271
Section-1 December 6541634 24964519 17944027 17944027
CPRI-Training Notes
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Section-2 190482 939975 887050 914992
Section-3 2594144 10794331 7107122 7118707
Section-4 9502 53443 53443 53443
Total 9335762 36752268 25991642 26031169
TABLE 3
TOTAL INPUT ENERGY
Sl. no Section Name Input (KWH), Nov Input (KWH), Dec.
1 Section-1 8560359.899 9481472.406
2 Section-2 1653488.836 1733845.982
3 Section-3 3120751.265 3468311.612
4 Section-4 3785000 4012000
Total 17119600 18695630
3.1.1.3. AT&C Loss:
Using the data tabulated in Table 1, Table 2. The Table 4 below shows the energy status
data of typical Town. The AT&C loss for the month November and December is given in the
Table 4 below
TABLE 4
ENERGY STATUS DATA CALCULATED BY CPRI
Descriptions Nov Dec
1 Input energy(kWh) 17119600 18695630
2 Metered Energy(kWh) 13968704 15305762
3 Billed energy(kWh) 13968704 15305762
4 Revenue billed in Rs 54009326 59652268
5 Revenue collected including arrear (LT) Rs 46637271 48831169
6 Revenue collected excluding arrear HT Rs. 46147824 48791642
1 Energy Loss% 18.41 18.13
2 Collection efficiency 86.35 81.86
3 Metering efficiency 81.59 81.87
4 Billing efficiency 81.59 81.87
5 ARR 2.72 2.61
6 AT&C loss 29.54 32.98
Excluding Arrear of HT
1 Collection efficiency excluding Arrear in HT 85.44 81.79
2 ARR 2.70 2.61
3 AT&C loss 30.28 33.04
CPRI-Training Notes
73
3.2 CASE STUDY -2
TECHNICAL LOSS ESTIMATION OF A FEEDER USING ETAP SOFTWARE
This study deals with Technical and Commercial losses in 11 kV feeder from A College 110
kV Substation which feeds a prominent Section of city in India through underground cables.
There are 12 transformers connected to this feeder. The feeder length is estimated to be 4.5
km.
3.2.1. ESTIMATION OF AT&C LOSSES
For estimation of AT&C losses, the feeder input is considered along with the revenue billed
and the revenue collected. The input energy of feeder is collected directly from feeder meter
available at substation and the output energy is taken directly from the
billed energy of the consumer and the revenue collected. Table 1 shows the list of
transformers and the energy billed for the particular transformer along with the revenue
collected for the study duration which is two months (Dec-06 and Jan-07). Table 2 shows the
results of the study. As shown in the Table AT& C is estimated to around 8.95 %. This feeder
is an urban feeder catering to both commercial and domestic consumers. DT meters have
been installed in this feeder.
TABLE 1
TRANSFORMER WISE ENERGY BILLED AND REVENUE COLLECTED
Sl. no Transformers Consumption in kWh Revenue billed
in Rs
Revenue
Collected in Rs
1 X-1 189942 674048 631583
2 X-2 218249 1180703 1098053
3 X-3 122486 450503 436989
4 X-4 139382 514319 496317
5 X-5 223147 822296 816181
6 X-6 138228 507987 494588
7 X-7 333824 734256 724523
8 X-8 167281 200117 195674
9 X-9 33126 187741 165986
10 X-10 203269 632974 622336
11 X-11 197465 612617 588112
12 X-12 73518 328396 304253
Total 2039917 6845957 6574595
TABLE 2
ESTIMATION OF AT&C LOSSES
Sl. No Particulars Dec-06 & Jan-07
1 Energy Input 2151520
2 Energy Billed 2039917
3 Revenue Billed 6845957
4 Revenue Collected 6574595
5 Collection Efficiency 96.04
6 Metering Efficiency 94.81
7 ARR (Rs/unit) 3.27
8 AT&C Losses % 8.95
CPRI-Training Notes
74
3.2.2 METHODOLOGY FOR TECHNICAL LOSSES
ETAP power system software is used for the load flow study of Kumarapuram feeder. Since
the software requires the exact length of UG cables, the mapping of the Kumarapuram 11 kV
feeder was conducted with the help of Global Positioning System (GPS 12). The distance
between the transformers is mapped to get the exact length of the feeder. Details of each
element in the feeder installed were collected. To run the load flow study, the
ETAP software requires the single line diagram of the feeder. The single line diagram is
drawn, showing Grid, Transformer, load on each transformer and exact length of UG Cable
etc. Following procedure is followed.
1. The load of the feeder is the peak load of the feeder obtained from the data
downloaded from the energy meter installed at this feeder.
2. Transformer data is collected from the name plate of the transformer available at site
and peak load of the transformer is measured during the peak time.
3. Transformer load is assumed as lumped load.
4. The type of cable installed is XLPE of 300mm² cross sectional area.
5. The tapping on secondary side of transformer is given from the data provided by the
utility
3.2.2.1 TECHNICAL LOSSES ESTIMATION
The technical energy losses of the distribution network were estimated by simulating the peak
load conditions on ETAP. The peak power losses for the network were assessed based on
load flow studies. The loss load factor was worked out from the daily load curve. The peak
power loss is converted to average energy loss by applying the loss load factor and the time
period of study. The feeder is simulated in the ETAP software by providing the Cable
lengths, the transformers installed along with their ratings and also the ratings of the
conductors etc. The peak load loss obtained by this simulation is taken to calculate the
average technical loss of the feeder along with Load Factor (LLF).
The Loss Load Factor is defined below
N
iNLLF
1
1Li² /Lmax²
Where N=48*31 = 1488
Li = Energy at Half an hour
Lmax = Maximum energy incident on the feeder / cable during the recording period
Table 3 shows the loss load factor calculation which is found to be around 0.37.
The Average Technical loss is calculated as I²Rt *LLF. The quantity I²R is available from the
load flow report of ETAP. The time parameter is taken as whole duration of study. Here it is
taken for 31 days. i.e. is 31*24 hours. Table 4 shows the technical loss calculations. The
average technical loss is 1.47 % and the peak load technical losses are around 1.54 %.
TABLE 3:
LOAD LOSS FACTOR CALCULATION
LLF Calculation
Lmax 909.94
CPRI-Training Notes
75
Lmax2 827990.8
∑Li2 460658120.7
N 1488
LLF=(∑Li2/Lmax)/N 0.37
TABLE 4
TECHNICAL LOSS CALCULATION
Peak input of feeder, P 2559 kW
Instantaneous peak load loss from ETAP,L1 39.4 kW
Peak technical loss in %=(L1/P)*100 1.54 %
Loss load factor,LLF 0.37
Average technical loss in kWh,L2=L1*31*24*LLF 10846 kWh
Total outgoing energy of feeder, S 737666 kWh
Technical energy loss %=(L2/S)*100 1.47 %
CPRI-Training Notes
76
3.3 CASE STUDY 3
TECHNICAL LOSS ESTIMATION OF A FEEDER USING CYMEDIST SOFTWARE
This study shows the load flow of a feeder carried out using the CYMEDIST software
3.3.1 INITIAL SURVEY:
A Pole to Pole survey of the feeder was carried out along with the GPS survey for HT lines.
The data so collected was digitised using Auto CAD with GPS Co-ordinates. The Auto CAD
drawing is imported through Attach Map Module in CYMEDIST Software and the network
simulated.
3.3.2 INPUTS FOR THE NETWORK
Following data the transformer obtained from the field study is given as an input to the digitised
feeder in the software
Conductors defined (Type of conductor, resistance & reactance, capacity etc.)
Transformers ( kVA rating, %Z, X/R ratio), Tap Position
Source (Zero sequence Impedance [Z0], Positive sequence Impedance [Z1])
Base MVA and base voltage is defined
3.3.3 SIMULATION METHODS
Popular methods of simulation are the kVA-pf and Amp-pf method. Current- power factor
method is used for this feeder and the Peak current on the sample feeder is used as the input
for the analysis for ―ampere-power factor method‖
A snapshot of the feeder is shown in figure below
FIGURE 1: SNAPSHOT OF THE FEEDER
CPRI-Training Notes
77
3.3.4 RESULTS
The results obtained using Amp-pf is tabulated below
4.0 CONCLUSION
Adoption of proper energy accounting and audit facilitates increased revenue realisation,
identification of areas and causes of high energy losses and cutting down on operational
inefficiencies. It also helps in bringing accountability and efficiency to the Utility. This also
helps in pinpointing losses due to technical reason and commercial reasons
Energy accounting and auditing could be carried out either directly with that data available
(viz. Input energy, Billed energy, energy sales etc.) or can be computed with the aid of
software(s) which would not only give the losses figures continually, but also throw up
problem areas in the distribution system like over loaded conductors, Transformers etc.
5.0 REFERENCE
1. Guidelines for development if Sub-Transmission and Distribution System‖ by Central
electricity Authority, Ministry of Power, Govt.Of India.
2. Estimation of Technical and Commercial Losses for Energy Accounting in
Distribution system, M M Babu Narayanan, Proc. of Best Practices in Distribution
Loss Reduction, DRUM Training Program, 2005
3. Estimation of AT&C losses for a typical losses for a typical town in Kerala, R. Sudhir
Kumar, M. M. Babu Narayanan et. al. , 22nd
National Convention Of Electrical
Engineers, Kochi, 2006
Trails Current(A) %Losses %
Loading
1. 120 1.4 17.4
2. 200 2.3 28.8
3. 300 3.4 42.6
4. 400 4.5 56
CPRI-Training Notes
78
Reliability&quality of power supply&reliability indices
P Chandrasekhar
Distribution Systems Division
Central Power Research Institute
Bangalore-India
Abstract--The electrical utilities are facing market conditions and therefore have to plan and operate their distribution systems in a cost effective way. This implies that the customer’s requirement on reliability i.e. availability has to be balanced towards the cost for obtaining the same. An effective way to solving this issue is by the use of quantitative assessment of reliability, i.e. reliability indices, which is based on probability theory. However these methods require input data that defines the condition for the system and its components. is to predict the future behaviour based on collected data and measured performance. The system Average Interruption Frequency Index (SAIFI) for Industrial feeder is 391.470interruptions/cust.yr and the System Average Interruption Duration Index(SAIDI) for Industrial feeder is 757.488 hrs/cust-yr.The system Average Interruption Frequency Index(SAIFI) for urban feeder is 578.761interruptions/cust.yr and the System Average Interruption Duration Index(SAIDI) for urban feeder is 731.342 hrs/cust-yr.The other indices are also evaluated.
The reliability assessment is normally used to evaluate performance of the distribution system network. The reliability of power Distribution system can be calculated by different reliability indices.This paper describes the reliability indices for two feeders of one is an industrial feeder and another one is an urban feeder. A software module (Reliability Assessment Module-RAM) has been used and the results of two practical distribution feeders are compared to benchmark the performance and operation of the power distribution system.
CPRI-Training Notes
INTRODUCTION
The distribution system is an important part of the total electrical supply system, as it is
provides the final link between a utility’s bulk transmission system and its customers. It has
been reported in some literature that more than 80% of all customer interruption s occur due
to the failure in the distribution system Though a single distribution system reinforcement
scheme is relatively inexpensive compared to a generation or a transmission improvement
scheme, an electric utility normally spends large sum of capital and maintenance budget
collectively on a huge number of distribution improvement projects [6].
Directly and indirectly customer satisfaction is concerned with thisImprovement and
modernization schemes of the transmission and distribution network. Reliability assessment
which was rarely an issue some time back is now generating waves in the management of
utilities. The customers who were tolerant earlier has become demanding more. Customers are
becoming conscious about the interruptions free service. They are started realizing that how
should get electricity in which they are also stakeholders of the entire system.
Reliability of a power distribution system is defined as the ability to deliver uninterrupted
service to customer. Distribution system reliability indices can be presented in many ways to
reflect the reliability of individual customers, feeders and system oriented indices related to
substation. To evaluate reliability in distribution system, two different approaches are normally
used; namely, historical assessment and predictive assessment. Historical assessment involves
the collection and analysis of distribution system outage and customer interruption data [4]. It
is essential for electric utilities to measure actual distribution system reliability performance
levels and define performance indicators in order to assess the basic function of providing cost
effective and reliable power supply to all customer types.
Historical assessment generally described as measuring the past performance of a system by
consistently logging the frequency, duration, and causes of system component failure and customer
interruptions. The historical data is very useful when analyzed to ascertain what went wrong in the past
and therefore correct it, and also as input to predict future service reliability [2]. Historical models
summarize the actual performance of a distribution system during some time period, for example,
quarterly, half-yearly or annually. The basic data item in this case is a system failure, which is a
component outage or a customer interruption. Each failure event is taken into consideration and
analyzed according to causes of failure, duration of outage, area of the system affected. A variety of
customer and load oriented system performance indices can be derived by analyzing the recorded data.
The reliability indices are very useful for assessing the severity of interruption events Assessment of
past performance is useful in the sense that it helps to identify weak areas of the system and the need
for reinforcement [6]. It enables previous predictions to be compared with actual field experience as
well as it can serve as a guide for acceptable values in future reliability assessments. The predictive
CPRI-Training Notes
reliability assessment can also help to predict the reliability performance of the system after any
expansion and quantify the impact of adding new components to the system.
The interruptions and duration of data is collected for Complete feeder
RELIABILITY INDICES
The most commonly used system indices
are [1].
System Average Interruption Frequency Index (SAIFI)
SAIFI = Total number of customer interruptions
Total number of customers served
SAIFI is the average number of interruptions
per customer served.
System Average Interruption Duration Index (SAIDI)
SAIDI =Sum of customer interruption duration
Total number of customers served
SAIDI is the average duration of a customer interruption, per customer served.
Customer Average Interruption Duration Index (CAIDI)
CAIDI =Sum of customer interruption durations
Total number of interrupted customers
CAIDI measures the average duration of a customer interruption within the class of customers that
experienced at least one sustained interruption.
Momentary Average Interruption Frequency Index (MAIFI)
MAIFI =Total no. of customer momentary interruptions
Total number of cutomers served
CPRI-Training Notes
Average Service Availability Index
ASAI = 1 − SAIDI
8760 ∗ 100
ASAI is the ratio of total customer hours that service was available, divided by the total customer
hours in the time period for which the index is calculated.
This paper describes the reliability indices SAIFI, SAIDI, CAIDI, MAIFI and ASAI etc., for
two practical feeders (industrial feeder & urban feeder) of an Indian utility.
METHODOLOGY
A. Historial Reliability Assessment
The basic techniques used inpower systemreliabil ityevaluationcanbe dividedinto two types-
analyticaltechniqueand numerical simulation technique. Analyticaltechniquesrepresentthe
systemby a simplifiedmathematicalmodel andevaluatethereliability indicesfrom
thismodelusingdirect mathematicalsolutions. In numerical simulation techniques; i t e s t i m a t e s
thereliabilityindices bysimulatingtheactual processandrandombehaviorofthe system. The
methodthereforetreats the problemas aseries ofrealexperimentsconductedinsimulatedtime.
Itestimates probabilityandotherindicesbycountingthenumberoftimes an eventoccurs. The
solutiontime foranalyticaltechniquesisrelatively short; as c o m p a r e d with numerical
s i m u l a t i o n techniquesthis is usually extensive.This disadvantagehas been partially
overcomebythedevelopmentof recentcomputationalfacilities. To evaluate reliability indices in
power system, some of the following methods are listedbelow
Network reduction
Markov modeling
Cut-Set method
Monte Carlo simulation
In this paper Cut-Set method based on failure modes has been used to evaluate the reliability
indices. The cut-set method is a powerful one evaluating the reliability of a system for two main
reasons.
It can be easilyprogrammed on a digital computer for the fast and efficient solution of any general
network.
The cut-sets are directly related to the models of system failure and therefore identity the distinct
&discreteways in which a system may fail.
CPRI-Training Notes
It can be defined as, a cut-set is a set of system components which, when failed, causes failure of the
system. In terms of reliability network or block diagram, the above definition can be interpreted as a set
of components which must fail in order to disrupt all pathsbetween the input and output of the
reliability network.
Figure.1 Minimal cut set of the system
The minimum subset of any given set of components which causes system failure is known as
a minimal cut-set. It can be defined as, minimal cut-set is a set of system components which,
when failed, causes failure of the system but when any one component of the set has not failed
does not causes system failure. The definition means that all components of a minimal cut-set
must be in the failure state to cause system failure.
TABLE.I MINIMAL CUT-SET OF THE FIG.1
Number of the minimal cut-set
Components of the cut-set
1 AB
2 CD
3 AED
4 BEC
B . Predictive Reliability Assessment
Predicting distribution system reliability performance is normally concerned with the electric supply adequacy at the customer load point. The basic indices used in practice are load point average failure rate (𝜆), average outage duration (r), and the average annual outage time (U). For a radial system, the basic equations for calculating the reliability indices at each load point “p” in a radial circuit are [2]
A C
E
D B
CPRI-Training Notes
𝜆𝑝 = 𝜆𝑖
𝑛
𝑖=1
𝑓𝑎𝑖𝑙𝑢𝑟𝑒𝑠/𝑦𝑒𝑎𝑟
𝑈𝑝 = 𝜆𝑖
𝑛
𝑖=1
× 𝑟𝑖 /𝑦𝑒𝑎𝑟
𝑟𝑝 =
𝑈𝑝
𝜆𝑝 /𝑓𝑎𝑖𝑙𝑢𝑟𝑒
Where n is the number of outage events affecting load point “p.” The steps associated with the predictive reliability calculation approach are summarized as follows.Calculate the reliability of each load point being serviced by a given distribution system configuration considering all interruption events and system constraints contributing to its unreliability for each year of the system.Calculate the system reliability indices with the help of calculated load point average failure rate, average outage duration and the average annual outage duration.
Repeat both the stepsfor all load points of the distribution system configuration under study and obtain the all the system indices SAIFI, SAIDI, CAIDI, ASAI, ENS, AENS etc.
CASE STUDIES
(1) Industrial feeder network
The practical distribution feeder which is taken from one of the Indian utility. This feeder network has
been modeled and simulated using CYMDIST-RAM software. It is an industrial feeder starting from
220/66/11kV substation, consisting of 74 Distribution transformers (DT’s) having 140 number of total
customers served with a total feeder length of 8.64 km.
(2) Urban feeder network
This urban distribution feeder is taken from one of the Indian power distribution utility which is
modeled and simulated using CYMDIST-RAM software.It is an urban feeder starting from 66/11kV
substation, consisting of 118 Distribution transformers (DT’s) having 6966 number of total customers
served with a total feeder length of 17.78 km.
(3) Outage data & Network data collection
Electric utilities have maintained LDC’s (Load Despatch Centre) for schedule & to despatch generated
power to the distribution utilities.The distribution Utilities are maintaining log books to interruption
details for all the feeders which are coming out from a particular substation and LC (Line Clearance)
book to enter the line clearance data.We have verified and collected the interruption details for a period
of one year from respective LDC’s and the substations, which includes the number of interruptions,
duration of the interruptions, cause for interruption, Location of fault in the feeder and equipment’s
failure data for both Industrial and Urban practical distribution feeders.. Feeder network has been
modeled in CYMDIST software module and Interruption details of the components are entered in the
feeder network at appropriate places, simulation carried out successfully and results are obtained.
CPRI-Training Notes
Figure 1 Single line diagram of typical industrial feeder network
Figure 2 Single line diagram of typical urban feeder network
CPRI-Training Notes
RESULTS AND ANALYSIS
The CYMDIST Reliability Assessment Module software is validated with IEEE-RBTS
Bus-Two system network. This is more significant to evaluate the performance of our
practical distribution feeders.
Table. II result shows the reliability indices of practical industrial feeder, urban feeder and describes the performance of the practical distribution networks. These results are helpful to the local utilities to provide quality of power supply at consumer end in reliable and cost effective manner. From fig.6 the SAIFI, SAIDI values give the system frequency and duration of interruptions per year per customer basis.MAIFI gives the momentary average interruptions per year per customer. Average system availability Index (ASAI), Average energy not supplied (AENS) and energy not supplied (ENS) indices will be helpful to the utilities for proper energy and asset management with respective kilowatt hour (kWh) loss. Reliability indices can vary from one place to another place according to the network configuration, geographical and weather conditions [6].
Table. II Historical Reliability Indices of
typical distribution feeders.
Sl.
No
Historical Reliability Indices
Industrial Feeder
Urban Feeder
1 SAIFI
(Intr/cust.yr) 403.430 757.441
2 SAIDI
(hr/cust-yr) 375.159 587.148
3 CAIDI
(hr/cust.Intr) 0.930 0.775
4 MAIFI
(Intr/cust.yr) 119.238 612.739
5 ASAI 0.9572 0.93302
6 ENS( kWh/yr) 816178.9 704517.0
7 AENS
(kWh/cust-yr) 5834.016 101.137
8 No.of Customers 140 6966
9 Line Length(km) 8.64 17.78
Table III shows the Predictive reliability indices for the Industrial and Urban feeder with the help of the historical data. One year historialinterruption data is used here to get the prédictive indices.
CPRI-Training Notes
Table III Predictive Reliability Indices of
typical distribution feeders.
Sl. No
Predictive Reliability Indices
Industrial Feeder
Urban Feeder
1 SAIFI
(Intr/cust.yr) 391.470 757.488
2 SAIDI
(hr/cust-yr) 578.761 731.342
3 CAIDI
(hr/cust.Intr) 1.479 0.965
4 MAIFI
(Intr/cust.yr) 48.064 612.723
5 ASAI 0.933398 0.91657
6 ENS( kWh/yr) 1259125.4 877447.1
7 AENS
(kWh/cust-yr) 9000.181 125.961
8 No.of Customers 140 6966
9 Line Length
(km) 8.64 17.78
Fig.3 indicates the comparison of SAIFI and SAIDI ofHistorical and Predictive Reliability assessment
for Industrial feeder.
Figure 3 Comparison of SAIFI and SAIDI for Industrial feeder.
0
100
200
300
400
500
600
700
Historical Predictive
SAIFI SAIDI
CPRI-Training Notes
Fig.4 indicates the comparison of SAIFI and SAIDI of Historical and Predictive Reliability assessment for Urban feeder.
Figure 4Comparison of SAIFI and SAIDI for Urban feeder
Fig. 5 shows the Energy Not Supplied (ENS) of both the Industrial and Urban feeders in Historical and Predictive assessment. The results shows that the value of ENS in Industrial Feeder is higher than those of Urban feeder due to the higher MW rating of Industrial feeder even though the SAIFI and SAIDI of Industrial feeder is low when compared to the Urban feeder.
Figure 5 Comparison of ENS in Historical and Predictive Reliability Assessment.
0
100
200
300
400
500
600
700
800
Historical Predictive
SAIFI
SAIDI
0
200000
400000
600000
800000
1000000
1200000
1400000
Industrial Feeder Urban Feeder
ENS
(MW
h/y
r)
Historical Predictive
CPRI-Training Notes
Conclusion
The out put of the results will be useful for planners of utility to decide whether new technologies or automation to be introduced for improving reliability system.
The results will be useful to keep the track of reliability indices for future expansion.
The results shows that it needs attention for the both industrial and urban feeders to improve reliability indices in future expansion of network.
The performance can be improved by proper system planning and analysis studies to
provide switches, sectionalizers and other protective devices at appropriate places.
Acknowledgment The authors are very grateful to the organization (CPRI) for permitted to do this research
work. The authors thankful officers and associates of the Distribution Systems Division
(DSD)who are directly or indirectly helped in execution of this project.
The authors also thankful to the local utilities for their cooperation and help to get
valuabledata and information in the field for the practical distribution network.
References [1] IEEE Guide for Electric Power Distribution Reliability Indices, IEEE Std 1366, 2011Edition. [2] A.A.Chowdhury, D.O.Koval, and S.M.Islam”Areliabilitybased model for electricitypricing” 2008
AustralasianUniversities Power Engineering Conference (AUPEC’08). [3] R.N.Allan, R.Billinton, I.Sjarief, L.Goel, and K.S.So “A reliability test system for
educationalpurposes-basic distribution system data and results”IEEE Transactions on Power Systems, Vol.6, No.2, May 1991.
[4] O.Shavuka,K.OAwodele,S.P.Chowdhury and S.Chowdhury “Reliabilityanalysis of distribution network” 2010 International Conference on Power System Technology.
[5] T.K.Vrana, Johansson, “Overview of power system reliabilityassessment Techniques”21, rue d’artois, F-75008 PARIS, Cigre-RECIFE2011.
[6] V Ashok, Harikrishna K V, P.Chandrasheksr, T.Raghunatha, ‘Performance Assessment in Power Distribution System based on ReliabilityIndices’, ICPES, Kaulampur-Malaysia 2013.
CPRI-Training Notes
ROCUREMENT POLICIES AND PROCEDURES
By: Praveen Shrivastava, Joint Director (Purchase), CPRI
1. Introduction:
Procurement is defined as the acquisition of appropriate goods in relation to goods /
services at the best possible total cost of ownership. The factors of quality and quantity
are taken into account in the act of procurement. Procurement is done to meet the
needs of the owner in terms of time and location.
2. Procurement Policies:
Policy is a statement of those principles and rules that are set by management as guides.
These are the general principles laid down for the guidance of executives who are
responsible for the procurement.
3. Procurement procedures:
3.1 Procedures is a series of steps to be followed during the process of procurement. The
procurement procedure to be followed plays vital role in reducing the financial outlay
of an organization or a company. It should be economically viable, with defined
period and with high level of transparency.
3.2 The procurement involves well defined procedure such as to collect technical
information from proper sources, to collect details pertaining to the manufacturer and
supplier with their back ground and to indenting, estimation of budgetary sanction and
estimated cost to identify goods according to the end use and application, to prepare
technical specifications, floating of NIQ/NIT.
4. Procurement Manual:
4.1 Organization policies and procedures are spelt out in the form of manual. It makes
policies and procedures authoritative and free from ambiguity. It defines
responsibilities and authorities and standardizes procurement procedures.
4.2 The procurement is broadly categorized as follows:
1) Indigenous procurement (in Indian rupees)
2) Import procurement (in Foreign currency)
4.3 The indigenous procurement is done within India and all the payments is done in Indian
rupees. An import is goods procured from foreign countries and the payments are
generally made through a letter of credit under various foreign currencies.
5. Import Procedure :
5.1 All goods are imported to India through air / sea transport.
5.2 All goods imported to India have to pass through procedures of customs department for
proper examination, appraisal, assessment and evaluation. This helps the custom
authorities to charge the proper duties, taxesand also to check the goods against illegal
import. Also, it is important to note that no import to India is allowed if the importer
CPRI-Training Notes
does not have the IEC Number issued by the DGFT (Directorate General of Foreign
Trade).
6. Types of contracts:
6.1 Project management contracts : The project management contracts are mainly divided
into two types viz., Rigid contracts and Flexible contracts.
The rigid contract is the type of contract most widely used by project management
consultants. This concept identifies a clear set of deliverables that the project manager
is expected to complete and submit to the client. These deliverables have a set time
table for when they must be completed. Using rigid contracts requires the ability to
accurately forecast the cost of project, as well as the ability to make sure the project
comes in under budget allocated.
The flexible contract offers a significant degree of flexibility on part of the client and
project manager alike. Flexible contracts are largely used by start-up companies which
try to cut costs where ever applicable as well as by companies who have projects that
involve a number of unknown and / or unpredictable variables. The below mentioned
contracts may be rigid or flexible.
6.1.1 Lump sum contract: When scope of work can be estimated in full detail.
6.1.2 Unit price contract: Where either contract or quantity is not clear or volume of work
cannot be precisely estimated.
6.1.3 Turn-key contract: A turnkey contract is a contract in which one party takes full
responsibility for the construction and commissioning of a plant. This also includes
the delivering of the plant in full working condition. The contractor assumes
responsibility from beginning to the end.On completion of the contract, the complete
system is handed over to the owner as per the terms and conditions of the contract.
In turn-key project, price adjustment clause is applicable because during this period the
commodity cycle may change due to National and International economical situation
such as fall and rise in Purchase Manager‘s Index (PMI),Core inflation, consumer
inflation growth cycle, labour consumption, variation in price for ferrous and non-
ferrous metal etc.. Price adjustment is eligible if the goods are delivered within the
scheduled delivery period. The price adjustment amount can be positive or negative.
If it works to be positive, the same is payable to the contractor by the owner. If it
works to be negative, the same is recovered by owner from the contractor.
7. Work schedule:
It should be given by the contractor in the form of bar chart for theentire period of
contract. The progress can be monitored accordingly. The bar chart should be self-
explanatory about the difference phases or area of work. The beginning of the work
schedule should be from the date of award of contract.
8. Quantity variation:
Generally 10 to 20% of quantity variation is permitted in turn-key projects due to
change in price of commodities.
9. Payment terms in turn-key projects:
CPRI-Training Notes
Generally the payment in the turn-key project is made in several stages depending on
the terms and conditions of the contract and progress of the work as per the bar chart
appended with the contract. The general stages of payment remitted is as follows:
a) Advance payment:10% against bank guarantee for the equivalent amount.
b) On shipment: 70% ex-works value of goods on proof of shipment.
c) Payment after commissioning: 10% after satisfactory installation and
commissioning.
d) Balance 10% after satisfactory and successful handing over of the system and
submission of performance bank guarantee to cover the guarantee / warranty
period.
10. Value of the contract:
The large contracts should be ordered preferably to single entity in order to avoid co-
ordination among different agencies which could cause time and cost over run.
11. Advertising:
Invitation to bid shall be advertised at least in one newspaper of general circulation.
The copies of such invitations or advertisement shall be sent to the local
representative of the eligible source countries .Advertisement should include all
necessary information such as subject matter of the bid, contract address, schedules,
funding source etc. It is essentially required to advertise in the following:
a) National news paper with high circulation in English.
b) National news paper with high circulation in Hindi.
c) Local news paper with high circulation
d) On website of organization, on the portal of Ministry of Power and Ministry of
State Government.
e) Information to all the Embassies which are widely participating in the tender.
f) Physical information and sending e-mails to all the known prospective bidders.
12. Qualification requirement to participate in bidding process:
12.1 The qualification requirement is an eligibility criteria to take part in the bidding
process such as to have the Company Registration, Sales Tax / VAT / CST number,
TIN Number, PAN Number, Service Tax Number, Registered Office, License of
import etc..
12.2 This also helps to assess the financial condition of the supplier so as to avoid delay in
supplies and other hurdles that may come. In view of the non-availability of the
above documents, the firm is not allowed to participate in the bidding process.
13. Pre-qualification requirement of Bids:
The Pre-qualification requirements are stipulated so as to get competitive bids from
experienced bidders for sophisticated and high value procurements. The pre-
qualification conditions are generally as follows:
a) Turnover of the company and number of similar orders that have been executed
in last three years or so.
CPRI-Training Notes
b) Strength of Organization set-up in case of contracts for services.
c) Branches / Service Centres in the country
d) Income tax returns for last three years or so to ensure healthy regular business.
e) Excise Duty / Sales Tax paid during last three years or so to the concerned
authoritiesetc, to assess volume growth of the company and to know
continuation of the business.
f) Performance Certificate of atleast few companies for last three years or so for the
similar contracts. Any additional conditions if deemed necessary may be
included.
14. Vendors qualification and development :
14.1 The organization with a sound vendor data base is successful in identifying the
appropriate vendor to procure the specific goods at a competitive price. The data
base is prepared with the help of web search, company profiles received from
various vendors, industrial product finders etc..
14.2 To create a data base, the organization can also publish advertisement inviting for
registration. The list of vendors can also be obtained from commercial department
and DGS&D. The introduction letters, mails, visiting / business cards, personal
interaction also helps to upkeep the records.
15. Preparation of Bid Documents:
15.1 The preparation of bid documents is an essential task to compile the documents viz.,
description of equipment, its technical specifications along with relevant drawings if
required, the general terms & conditions, commercial terms & conditions, special
conditions if any, bid security form, format for Performance Bank Guarantee,
Government taxes, duties, incidentals etc..
15.2 The correct sequence of preparing the bid document will result in getting the
competitive offers avoiding the ambiguity as far as possible thereby comparing the
techno-commercial bids becomes easy for evaluation.
16. Tendering / Bidding:
16.1 Single Envelope Bidding:
16.1.1 Generally, for NIQ also called Limited Tender Enquiry, Single envelope bidding is
invited for certain defined value of procurement, generally low which depends on
procurement procedure of an organization.
16.2 Two envelope bidding:
For works, machinery and equipment for which complete technical specifications
are prepared in advance this type of bidding is adopted. Under this procedure,
bidders will be invited to submit technical and price proposals simultaneously in
two separate envelopes.The technical proposals are opened first and reviewed to
determine that they confirm to the specifications. After technical evaluation the bids
of only technical suitable offers will be opened publicly with bidders or their
CPRI-Training Notes
representatives allowed to be present. Price proposals of technically non suitable
offers shall promptly returned un opened.
16.3 Three Envelop Bidding:
The three envelope bidding is similar to the two envelope bidding except that the
first envelop consisting of Tender Fee and EMD is opened. Subsequently, the
technical proposals of only such tenderers will be opened who have submitted the
requisite tender fee and EMD.
16.4 Two stage bidding:
16.4.1 This type of bidding is adopted in the case of turnkey contracts for large and
complex plants or procurement of equipment which is subject to rapid technological
advances for which it may be impractical to prepare complete technical
specifications.
16.4.2 Under this procedure, technical bids will be first invited without prices on the basis
of the minimum operating and performance requirements. After commercial and
technical clarifications and adjustments followed by amended bidding documents
the bidder will be invited to submit final technical proposals and price bid in the
second stage.
17. Earnest Money Deposit (EMD):
EMD will usually be required, but they shall not be set to so high as to discourage
suitable bidders. EMD shall be released to unsuccessful bidders as soon as possible
after the bids have been opened. The internationally accepted amount of bid security
is around 2% of the estimated cost.
18. Requirement of Addendum:
In case where there is a need to change the specification due to some technical
reason by bid issuing authority, then these modifications are necessarily be sent to
all those bidders who have bought the tender and are requested to sendthe addendum
to the main bids before due date of opening or extended date of opening.
19. Bid Opening and Evaluation:
19.1 Duration to submit Bids:
19.1.1 The time allowed for preparation of bids shall be determined with due consideration
of the circumstances of the project and the size and complexity of the contract.
Generally, not less than 45 days shall be allowed for any type of NIT and for NIQ
minimum 15 to 30 days shall be allowed.
19.1.2 For Open Tender (Worldwide Publicity) where large civil works or complex items of
equipment are involved, generally not less than 90 days shall be allowed to enable
bidders to investigate at the site before submitting their bids.
19.2 Procedure to open bids:
19.2.1 The date, time and place of receipt and opening of bids shall be indicated in the
invitations to bids. All the bids shall be opened publicly at the stipulated time and
place by tender opening committee in the presence of representative of the bidders.
CPRI-Training Notes
Bids received after the time shall be returned unopened. The name of the bidder and
total amount of each bid should be read and recorded.This record shall be confirmed
and signed by all bidders or their representatives present at the time of opening of
bids.
19.2.2 No bidders shall be permitted to alter his bid after the bids have been opened. Only
clarifications not changing the substance of the bids are acceptable as and when
required.
19.2.3 Except as may be required by a law, no information relating to the evaluation of bids
and recommendation concerning awards shall be communicated to any persons until
a contract has been awarded to a bidder.
20. Examination of bids:
20.1 Examination shall be made in respect to formality, in areas such as material errors in
computation; conformity to specifications required in the bidding documents, proper
signatures and required EMDs. If any deviation from the above requirements or
when large discrepancies are found the bid concerned should be rejected in light of
the fundamental rules of bidding.
21. Rejection of Bids:
21.1 Rejection of all bids may be justified when (a) no bid is substantially responsive to
the bidding documents or (b) there is a lack of competition.
21.2 If all bids are rejected, buyer shall review factors that made such rejection necessary
and consider either revision of the specifications or modification of the project.
23. Evaluation and Comparison of Bids:
23.1 Among the bids which confirms to the technical specifications, the bid with the
lowest evaluated cost , not necessarily the lowest submitted price, shall be selected
for award.
23.2 Bids evaluation should be consistent with the terms and conditions set forth in the
bidding documents. Factors which may be taken into consideration include, inland
transportation, payment schedule, time of completion, operating costs, compatibility
of the equipment, availability of service and spare parts,safety,environmental
benefits etc.Provisions for price adjustment included in a bid shall not be taken in to
consideration, particularly for the procurements pertaining to non-works items.
23.3 Bidders will be required to state in their bids the CIF port of entry price for imported
gods or the Ex-factory price for other goods.
Customs duties and import taxes and similar taxes shall be taken in to account in the
evaluation of the bid.
The cost of inland freight and other expenditures incidental to the transportation and
delivery of the goods shall be included if this is specified in the bidding document.
23.4 An inspection of bidder‘s factories during the bid evaluation is acceptable provided
the buyer pays the entire cost of such inspection or as agreed between the buyer and
the bidder.
CPRI-Training Notes
24. Award of contract:
The contact is to be awarded to the bidder whose bid has been determined to be
technically meeting the requirement of specification and also to be the lowest
evaluated bid and who meets appropriate standards of capability and financial
resources.An example of factors constituting a contract is: Contract agreement,
Letter of Acceptance, Bid and Appendix to bid, conditions of contract,
Specifications, Drawings, Bill of Quantities.The award of a contract is notified to the
successful bidder by a Notice of Award, Letter of Intent, or Letter of Acceptance.
25. Currency conversion for Bid comparison:
For the purpose of comparing prices, all bid prices shall be converted to a single
currency selected by the buyer and stated in the bidding documents. The buyer shall
effect this conversion by using the exchange rate (selling) quoted by an official
source (such as the central Bank). The date prescribed in the bidding documents
should be used to prevent an arbitrary decision.
26. Currency of payment in case of imported goods:
Payment of the contract price shall be made in the currency is expressed in the bid of
of the successful bidder. The exchange rate to be usedfor the purpose of payment
shall be that specified by the bidder in the bid.
27. Price Adjustment clauses:
Is generally applicable in turn-key project whose Bidding documents shall clearly
state whether firm prices are required or adjustment of bid price is acceptable.
Specific formula for price adjustment shall be clearly stated in the bidding
documents. There should normally be no price adjustment provision for goods
pertaining to supply of non-works items. The bid with price variation clause when a
fixed price was called, may be treated as disqualified and rejected.
28. Guarantees, Performance Bank Guarantee and Retention money:
Bidding documents shall insist a performance security in the form of Bank
Guarantees to protect the buyer from default by the supplier. The amount may vary
depending on the case and is between 5 and 15% of the contract price and the
validity period normally about one year after completion of work and
commissioning or may be more as mentioned in the Bid document.
29. Liquidated damages:
Liquidated damages clause shall be included in the bidding documents for delays in
completion of delivery resulting in extra cost, loss of revenue etc.The percentage of
liquidated damages should be about 0.5% per week to a maximum of 5% of the
contract price.
30. Closing of contracts:
The contract is considered as closed when it is handed over to the owner after
successful installation and commissioning of the complete project. However, the
contractor shall furnish the Performance Bank Guarantee for the period defined in
the contract so as to cover the guarantee / warranty of the project.
CPRI-Training Notes
31. Force Majeure:
The conditions of contract included in the bidding document shall contain clauses
stipulating that failure on the part of supplier to perform their obligations under the
contract will not be considered as default if such failure is the result of force majeure
in the conditions of the contract.
32. Language:
Bidding documents should be prepared in English for International contracts and
Bilingual for Indian contracts. If another language is useda full English text shall be
incorporated in those documents.
33. Settlement of disputes:
Provision dealing with the settlement of disputes shall be included in the conditions
of contract. It is advisable that the provision be based on the ―Rules of Conciliation
and Arbitration‖ prepared by the International Chamber of Commerce. The contract
shall stipulate which laws shall govern its interpretation and performance.
CPRI-Training Notes
Distribution Reforms in India: APDRP, R-APDRP &RGGVY
Viji Bharathi, Engineering Officer, Distribution Systems Division, CPRI
1.0 Introduction
In India, restructuring of the power sector was felt due to the scarcity of financial resources
available with Central and State Governments and the necessity of improving the technical
and commercial efficiency of the Electricity distribution. Due to lack of adequate
investment on Transmission and Distribution (T&D) works, the T&D losses had been
consistently on the higher side. To lead the reforms the Regulatory Commissions were
formed in 1998 under the Electricity Regulatory Commissions Act 1998 (Central Law) to
promote competition, efficiency and economy in the activities of the electricity industry.
Ministry of Power, Government of India has undertaken reforms in power sector with a step
by the Electricity Act 2003 and then during the X five year plan, the ―Accelerated Power
Development Programme‖ (APDP) was launched in 2001-02 and was renamed as
―Accelerated Power Development and Reforms Programme (APDRP)‖ was launched in
2002-03. Another scheme,―Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY)‖ was
launched during April 2005. The main aim of APDRP was restoring the economic viability
of the state utilities and that of RGGVY is to provide Rural Electrification Infrastructure and
Household electrification.
2.0 Overview
The objective of reforms is to bring in commercial viability in the power sector so as to
ensure power supply on demand to all consumers at reasonable rates. The main features of
the reforms strategy involve [2]:
i) Functioning of Regulatory commissions in the states. A credible independent
Regulatory commission is a primary requisite for generating confidence for private
investment on a significant scale.
ii) Full audit of energy flow at all levels so as to accurately identify where the energy is
being consumed or lost. This would require metering at all substations and feeders.
iii) Effective elimination of power thefts. All consumers of power need to be metered in a
time bound programme.
iv) Tariffs which provide for commercial viability. The state governments would need to
provide explicit subsidies for large groups as cross subsidy beyond a point is not
sustainable.
v) Design and implementation of cost-effective investment for improving the sub
transmission and Distribution network to reduce avoidable technical losses.
CPRI-Training Notes
3.0 Accelerated Power Development and Reforms Programme (APDRP)
The Accelerated Power Development Reforms Programme (APDRP) was launched in 2002-
03 with additional central financial assistance to the states to strengthen and upgrade the
sub-transmission and distribution systems of high-density load centres like towns and
industrial areas with main objectives of reduction in AT& C losses; improve quality and
reliability of power supply. Total 574 projects at the cost of Rs.17329.07 Crore were
sanctioned in 10th Plan APDRP. On implementation of APDRP, the AT & C losses could
be brought down below 20% in 215 towns (163 towns less than 15% & 52 towns between
15-20%) in the country.
3.1 Main Objectives
The main objective of APDRP was to bring down the AT&C losses to below 15% in urban
and high density areas.The other objectives being: improving customer satisfaction,
increasing reliability of power supply, improving quality of supply, adopting systems
approach with MIS, and bringing transparency through computerisation.
The concept of Aggregate Technical and Commercial (AT&C) losses was introduced as the
T&D loss was not able to capture all the losses in the network.
3.2 Initiatives/ Inventions for achieving the objectives:
Commercial: Commercial activities target reduction of commercial losses and
improvement of revenue through Indexing of consumers to distribution transformers,
installation of tamper proof meters at all levels of transformation of electricity and for all
consumers, Operationalizing energy audit & accounting up to LT feeder level by index
linking, de-centralized billing & collection.
Technical: Technical activities required detailed system analysis to evaluate cost-effective
options for system up gradation and improvement, technical loss reduction and voltage
profile improvements. This involved augmenting/ upgrading over loaded/ failure prone
network elements like transformer, feeder, capacitor etc., to minimize interruptions, moving
towards LT less system with the object of progressively achieving high voltage distribution
system (HVDS), installation of small capacity energy efficient distribution transformers, re-
conductoring of over loaded lines, power factor correction, IT aided monitoring and control
(MIS), GIS mapping etc.
Organizational: This involved reorganizing the manpower at the circle level from the
Superintending Engineer to Junior Engineer and fixing duties, responsibilities and
accountability at each level with a clear line of command. It also involved the activities like
integration of technical, commercial and administrative functions at the circle and 11kV
feeder level to enable circles and feeders to operate as profit centres and business units
CPRI-Training Notes
respectively. The billing collection mechanism was to be decentralized to the feeder level
with a system of incentives for the staff at the circle and the feeder level for efficiency in
billing and collection targets.
Capacity Building:To assist the State Electricity Boards (SEBs)/ Utilities in technical and
management skills to enable them to formulate and implement circle level distribution
projects, Ministry of Power had appointed National Thermal Power Corporation Ltd.,
(NTPC) and Power Grid Corporation of India Ltd., (PGCIL) as lead Advisor-cum-
Consultants (AcCs). Their responsibilities were to assist in capacity building in the SEBs
by focusing on the activities required for undertaking the commercial, technical &
organizational measures required in the short terms and long terms in addition to
supervising the project implementation.
3.3 Projects sanctioned under APDRP
Projects included major towns and industrial areas across the country including various
states in addition to the 63 circles which were originally identified in 2000-01 to be
developed as centres of excellence. These circles had certain short & long term measures to
be considered essential to meet the objectives of the programme. These are to be developed
as pilot projects and made suitable for replication in the other parts of the country.
During 2002-03, projects involving major towns and industrial areas were sanctioned to
fulfil the short-term objectives i.e., revenue increase and outage reduction.
3.4 Steps for implementation of APDRP
The following steps were involved the following through Memorandum of Understanding
(MoU) and Memorandum of Agreement (MoA):
(i) Setting up of State Electricity Regulatory Commission (SERC)
(ii) Restructuring of State Electricity Boards (SEB)
(iii) Administrative measures for improvement
(iv) Delegation of powers & duties
(v) Metering up to 11 kV feeder level and energy accounting
(vi) 100% Metering of all consumers
(vii) Computerisation of SEB commercial and technical functions
(viii) Adoption of turnkey contracts for APDRP implementation
(ix) Agricultural tariff policy and subsidy by State Government and
(x) Adoption of unit wise commercial accounting practices.
Preparation of DPR: The Detailed Project Report (DPR) was prepared containing the data
in accordance with the ―Guidelines for strengthening of sub-transmission & distribution
system‖ issued by the Committee of experts. The DPR included the methodology and time
schedule for execution of the works, fund flow requirements, prevailing benchmark
parameters for assessing the performance etc. The DPR was to show the cost benefit
CPRI-Training Notes
analysis and sensitivity analysis on critical parameters assumed for financial viability of the
project. The same approved by MoP and checked by the Financial Institutions was
forwarded to Ministry of Finance (MoF) for release of the sanctioned funds based on the
MoA.
3.5 Funding Mechanism
Projects worth Rs.15,642Cr approximately were sanctioned initially which were to be
implemented within 2-3 years. The APDRP investment component was estimated to be
around Rs.20,000 Cr. Additional Rs.20,000 Cr was considered for incentive for cash loss
reduction to encourage the State Utilities and disbursed pro-rata based on actual
performance on ground.
The funding modalities were:
Sl.No. Category of States % of Projects/ Scheme Cost
from APDRP as
% of Projects Scheme
Cost from PFC/ REC/
Own/Other Sources Grant Loan
1 Special Category States 90 10 -
2 Non-special Category
States 25 25 50
APDRP was used as an instrument to leverage reforms in the State power sector. Thus the
funds under APDRP were released only to those States which had executed a MoU with the
Ministry of Power (MoP) committing to a time-bound reforms and restructuring process in
the State power sector.
3.6 Advisor cum Consultants
In the first phase AcCs were appointed to assist States in formulation of DPR and oversee
the implementation of the project. During November 2001, NTPC and Power Grid were
identified as the lead AcCs where CPRI, MECON, WAPCOS, NPC and ERDA were
brought under them as AcCs.
3.7 Status of APDRP
The APDRP scheme fell short of expectations, with the result of over Rs.176.12 billion
worth of projects sanctioned till March 2005, total investment was only Rs.57.68 billion or
just 32.75 per cent. Also, it was seen that while the target of reducing AT&C losses was
CPRI-Training Notes
from around 40 per cent to 15 per cent over five years, the actual reduction was not more
than 5 per cent, that is 35 per cent. Even then, the AT&C losses varied widely between
states from 18 per cent to as much as 60 per cent.
It was because of this that the Central Government came out with the R-APDRP scheme,
with the aim of restoring the commercial viability of the distribution sector by putting in
place mechanisms that lead to a substantial reduction in Aggregate Technical and
Commercial (AT&C) losses on a sustainable basis.
3.8. Conclusions
The success of APDRP in establishing the financial viability of the distribution system can
be improved depending on the choice of elements to be funded, speed of execution,
organizational commitment and public, political as well as administrative support. A
scientific result oriented approach is to be adopted while formulation of the schemes for
funding. Since the programme is result oriented, necessity for setting up of the bench marks
to be achieved and the mechanism for achieving the same arises. The six level interventions
for implementation were not really successful at all levels. There was a delay in release of
funds from the states to the utilities. The results of the programme could not be measured to
a reliable extent due to lack of baseline data. Realizing the shortcomings of APDRP, the
Government came up with another programme, the ―R-APDRP‖ to overcome the
shortcomings of APDRP.
4.0 Restructured APDRP (R-APDRP)
The Govt. of India proposed to continue R-APDRP during the XI Plan with revised terms
and conditions as a Central Sector Scheme. The Programme started during 2008-09 with the
main objective of reducing the Aggregate Technical and Commercial (AT&C) losses with a
focus on actual, demonstrable performance in terms of sustained loss
reduction.Establishment of reliable and automated systems for sustained collection of
accurate base line data and the adoption of Information Technology in the areas of energy
accounting will be essential before taking up the regular distribution strengthening projects.
4.1Programme Coverage
It is proposed to cover urban areas - towns and cities with population of more than 30,000
(10,000 in case of special category states). In addition, in certain high-load density rural
areas with significant loads, works of separation of agricultural feeders from domestic and
industrial ones and of High Voltage Distribution System (11kV) will also be taken up.
Further, towns / areas for which projects have been sanctioned in X Plan R-APDRP shall be
considered for the XI Plan only after either completion or short closure of the earlier
sanctioned projects.
4.2Proposed Scheme
CPRI-Training Notes
Projects under the scheme shall be taken up in Two Partsi.e. Part-A and Part-B. Part-A shall
include the projects for establishment of baseline data and IT applications for energy
accounting/auditing & IT based consumer service centres. Part-B shall include regular
distribution strengthening projects. The activities to be covered under each part are as
follows:
Part - A: Preparation of Base-line data for the project area covering Consumer Indexing,
GIS Mapping, Metering of Distribution Transformers and Feeders, and Automatic Data
Logging for all Distribution Transformers and Feeders and SCADA / DMS system (only in
the project area having more than 4lakhs population and annual input energy of the order of
350 MU). It would include Asset mapping of the entire distribution network at and below
the 11kV transformers and include the Distribution Transformers and Feeders, Low Tension
lines, poles and other distribution network equipment. It will also include adoption of IT
applications for meter reading, billing & collection; energy accounting & auditing; MIS;
redressal of consumer grievances; establishment of IT enabled consumer service centres etc.
The base line data and required system shall be verified by an independent agency
appointed by the Ministry of Power.
Part- B: Renovation, modernization and strengthening of 11 kV level Substations,
Transformers/Transformer Centres, Re-conductoring of lines at 11kV level and below, Load
Bifurcation, feeder separation, Load Balancing, HVDS (11kV), Aerial Bunched
Conductoring in dense areas, replacement of electromagnetic energy meters with tamper
proof electronic meters, installation of capacitor banks and mobile service centres etc. In
exceptional cases, where sub-transmission system is weak, strengthening at 33 kV or 66 kV
levels may also be considered.
Part - C: An enabling component for the implementation of APDRP and for facilitating the
process of reforms in the power sector. This part, to be implemented by Ministry of Power/
PFC, will include:
Preparation of a template for System Requirement Specifications for sub-division
automation and for customer relations management module, as well as for automated
baseline data collection systems.
Validation of the Baseline Data System to be done by independent agencies identified
through bidding process by the Ministry or its nominee. Independent agencies will also
verify the AT&C losses and monitor quality of works to be executed under Part-B.
Project Advisors and Project Management Consultants – Project advisor and project
management consultants will be appointed to assist the Ministry in monitoring of
APDRP and to validate the project proposals submitted by the Distribution companies.
They will also facilitate in standardisation of bidding/contract documents, monitoring of
progress, quality assurance etc. They will also facilitate the Management Information
System.
CPRI-Training Notes
Project Evaluation by Third Part Introduced in the X Plan will continue and will be the
basis of computation of the extent of conversion of loan into grant for the specific
project. A panel of Project evaluators will be finalized through a bidding process.
Capacity Building and development of franchisees in Distribution sector will be a major
focus area to provide training to employees of the Distribution companies and existing
&prospective franchisees in management, technical, commercial and consumer related
areas, exposure to latest developments in electricity distribution, loss reduction, theft and
pilferage control within India and abroad, dissemination of knowledge through Best
Practice Workshops and Conferences, standardization of specifications of equipment
required in electricity distribution network, standardisation of contractual documents for
outsourcing project management, turnkey jobs, franchising etc.
Consumer Attitude Survey will be carried out to assess the impact of the measures taken
in the distribution sector towards improving of services, improving the reliability and
quality of power supply.
4.3Eligibility Criteria for R-APDRP assistance
The States / Utilities will be required to:
1) Constitute the State Electricity Regulatory Commission for availing assistance under re-
structured APDRP.
2) Achieve the following target of AT&C loss reduction at utility level:
a) Utilities having AT&C loss above 30%: Reduction by 3% per year
b) Utilities having AT&C loss below 30%: Reduction by 1.5% per year
3) Commit a time frame for introduction of measures for better accountability at all levels
in the project area
4) Submit previous year's AT&C loss figures of identified project area as verified by an
independent agency appointed by Ministry of Power (MoP).The independent agency
would verify that:
a) All input points are identified and metered with downloadable meters for energy
inflow accounting in scheme area
b) All outgoing feeders are to be metered in substation with downloadable meters
c) Scheme area should be ring fenced i.e. export and import meters for energy
accounting shall be ensured besides segregating the rural load of the scheme area by
ring fencing if not on separate feeder
CPRI-Training Notes
d) The above shall provide the input energy and corresponding cash collected for
calculating AT&C losses. The same shall be carried out for at least for three billing
cycles and got verified by the independent agency. This loss level will be the
baseline for considering conversion of loan into grant for Part B projects
5) Devise a suitable incentive scheme for staff in the project area linked to achievements of
milestones.
4.4Funding Mechanism
Part – A: Initially 100% funds for the approved projects shall be provided through loan
from the Government of India on the terms decided by Ministry of Finance. The loan shall
be converted into grant once the establishment of the required system is achieved and
verified by an Independent agency.The interest on the converted loan shall be capitalised.
No conversion to grant will be made in case Part A is not completed within 3 years from the
date of sanctioning of the project. The project will be deemed to be completed on the
establishment of the required system duly verified by an independent agency appointed by
Ministry of Power(MoP).
Part – B: Initially upto 25% funds for the projects shall be provided through loan from the
Government of India (GoI) on the terms decided by Ministry of Finance. For special
category States, GoI loan would be 90%. However, the project-wise requirement of Gross
Budgetary Support will be decided by the Steering Committee. The balance funds shall be
raised from Financial Institutions (FIs). All other conditions/ methodology applicable to
non-special category states shall also be applicable to the special category states. If
distribution Utilities achieve the target of 15% AT&C loss on a sustained basis for a period
of 5 years in the project area and the project is completed within the time schedule fixed by
the Steering Committee, which shall in no case exceed five years from the date of project
approval upto 50% (90% for special category states) loan against Part B projects will be
convertible into grant in equal tranches, every year for 5 years starting at the latest one year
after the year in which the Part A of the project area concerned is established and verified
by the Independent Agency appointed by MoP. If the Utility fails to achieve or sustain the
15% AT&C loss target in a particular year, that year‘s tranche of conversion of loan to grant
will be reduced in proportion to the short fall in achieving 15% Aggregate Technical and
Commercial (AT&C) loss target from the starting baseline assessed figure. The interest on
the converted loan from GoI and FIs will be capitalized on an annual basis. Illustration is
given through a typical example as shown below:
Typical Example:
Take the example of a distribution utility from a non –special category state whose starting
AT & C loss figure is 60% in the year 2008-09, the year in which the base line data system (
Part A ) is established and verified by the independent agency appointed by MoP .If this
distribution utility archives and sustains the 15% AT & C loss level for a period of 5 years
after the grace period of one year i.e. 2009-10,one fifth of the 50% loan shall be converted
into grant each year from the year 2010-11 onwards. However, if this distribution utility
CPRI-Training Notes
could only achieve AT & C loss figures of 30%, 40%, 30%, 15% and 20% in 1st, 2
nd, 3
rd,
4th
& 5th
year respectively of the period in question, the year wise loan conversion into grant
shall be as follows:
2010-11 1st year: (60-30)/60-15) i.e 2/3 of annual tranche (1/5 of 50% loan i.e
10% of project cost) shall be converted into grant.
2011-12 2nd
year:(60-40)/(60-15) i.e. 4/9 of annual tranche (1/5 of 50% loan i.e. 10%
of project cost)shall be converted into grant.
2012-13 3rdyear: (60-30)/(60-15) i.e. 2/3 of annual tranche (1/5 of50% loani.e.10% of
project cost) shall be converted intogrant.
2013-14 4th
year: (60-15)/(60-15) i.e.full annual tranche (1/5 of 50% loan i.e.
10% of project cost) shall be converted into grant.
2014-15 5th
year : ( 60-20)/(60-15) i.e. 8/9 of annual tranche ( 1/5 of 50% loan i.e.
10% of project cost ) shall be converted into grant.
4.5Sanction Process
The sanction process and other formalities for execution of Part A and Part B components
can be taken up simultaneously except that Part B activities are likely to start 3-6 months
after the start of Part A for making arrangements of ring fencing for the project area and
verification of the starting figure of AT&C loss of the project area by Independent Agency
appointed by MoP with three billing cycle data. This may not be necessary where ring
fencing of the project area has already been done by the state utilities except for the time
required for verification of the starting figure of AT&C loss of the project area. This would
help the utilities to reduce the overall project execution cycle.
Conversion into grant will take place annually based on AT&C loss figures of the project
area as on 31st Mar duly verified by the Independent Agency appointed by MoP.
Incentive Scheme for Utility Staff: Scheme also envisages incentive for Utility staff in
towns where AT&C loss levels are brought below 15%. Each Distribution company will be
required to implement an incentive programme for utility employees of the specific project
area. Details of the incentive scheme and the milestones/achievements that trigger incentive
payments shall be agreed to project proposals presented by each utility. A maximum
amount equivalent to 2% of the grant for Part B project is allocated for this purpose. The
utility is expected to match these funds and disburse the total amount among its employees
according to a suitably devised incentive scheme. Each utility must submit a duly approved
incentive scheme prior to seeking disbursements under Part-B. State Governments and
distribution companies will work with the concerned regulator to ensure that a part of the
financial benefits arising out of the AT&C loss reduction are also passed on to the
consumers of the project area.
CPRI-Training Notes
4.6The modalities of formulating / implementing projects under the
programme are as under:
1. Project Formulation: The utilities shall prepare Detailed Project Reports (DPRs) in two
parts (i.e. Part –A & Part-B) for each of the project areas and while forwarding the DPRs
to the Nodal Agency indicate the order of priority of the projects. Utilities may appoint
IT Consultants through bidding from an open bidding process from the panel of IT
consultants prepared by the Nodal Agency for preparing DPRs of Part-A projects. IT
consultants shall be empanelled by the Nodal Agency / MoP after observing formalities.
Utilities may also prepare DPRs for Part-A on their own in case they feel that they have
the skill and expertise to do so. Hiring charges of the IT Consultant may be included in
the project cost of Part-A only if an IT consultant is appointed from the panel prepared
by the Nodal Agency and same is appointed through competitive bidding. DPRs for Part-
A shall be submitted by utilities along with an undertaking indicating that the DPR is
duly verified either by the IT Consultant so appointed or else by the utility itself. These
DPRs shall be submitted to PFC, the Nodal Agency. These DPRs will be validated and
appraised techno- commercially by PFC and will then be submitted to the APDRP
Steering Committee for approval. Further guidelines as required for formulation of
projects would be issued by Ministry of Power from time to time.
2. Implementation: SEBs / State utilities shall implement projects sanctioned under this
programme on a turnkey basis by appointing the IT Implementing Agencythrough a
bidding process only from the Panel of IT implementing Agenciesnotified by the Nodal
Agency to ensure quality and expeditious implementation. IT implementing agencies
shall be empanelled by the Nodal Agency / MoP after observing nodal formalities.
Further guidelines as required for implementation of projects would be issued by
Ministry of Power from time to time.
3. Quadripartite Agreement: A Quadripartite Agreement will be entered into between
SEBs / Utilities, GoI, PFC and the State Government to implement the re-structured
APDRP. Signing of Quadripartite Agreement is a prerequisite for release of funds under
re-structured APDRP. The Ministry of Power / PFC will monitor implementation of
precedent conditions agreed to in the Quadripartite Agreement before releasing funds. If
considered necessary, Ministry of Power may impose such conditional ties as it deems fit
for the implementation of re-structured APDRP from time to time.
The programme would be of the size of Rs.51,577Crores under Central Sector Scheme.
Initially Rs.50,000Crores will be provided / arranged as loan from GoI/ FI‘s out of which as
estimated amount of Rs.30,000 Crores would be converted into grant. The total grant from
GoI is estimated as Rs.31,577 Crores. However the actual requirement would depend on the
achievements of targets by the utilities.
a) Rs.50,000 Crore for Part A and Part B of the projects.
Rs.10,000 Crore for Part A activities
CPRI-Training Notes
Rs.40,000 Crore for Part B activities
b) Rs.1,177 Crore for enabling activities to be implemented by MoP (Part-C)
Rs.850 Crore for the services rendered by the Nodal agency
Rs.200 Crore for capacity building and franchisee development exposure to latest
developments in electricity distribution within India and abroad
Rs.50 Crore for few pilots for adopting new innovations
Rs.77 Crore for miscellaneous activities such as ―Best Practices‖ workshops and
conferences; Consumer Attitude survey, Project Specific Evaluation; Standardisation of
specifications of equipment and contractual documents
c) Rs.400 Crore for incentive to Utility Staff of the project areas for establishment of
baseline data and for achieving targeted reduction in AT&C loss.
4.7General terms and conditions for utilisation of funds
The funds under the programme will be provided to the State Power Utility/Distribution
Company through PFC, the Nodal Agency. Budget provision for the funds shall be made
annually.
State Power Utility/Distribution Company receiving APDRP assistance will have to open a
separate account/ sub account head immediately, for separate accounting classification, both
on the receipt and expenditure side for enabling proper Audit Certification, including
escrow account in the bank.
The reduction of T&D losses as part of overall AT&C losses would also enable the utilities
to claim carbon credits for avoiding power generation under CDM mechanism subject to
necessary approvals. The state utilities will be encouraged to take advantage of CDM
benefits for reducing the cost of the scheme and making it financially viable. A cell for
facilitating the same shall be created in the Nodal Agency.
The loan under the programme through GBS from GoI shall be subject to the terms and
conditions laid down by the Ministry of Finance/ GoI at the time of release.
Funds provided to the State Power Utility/ Distribution Company under APDRP cannot be
diverted to any other scheme or used for any other purpose.
The State Governments/ State Power Utilities would be required to submit to PFC/MoP
monthly progress report in respect of the progress of execution of project, fund Utilization
by the State Power Utility/Distribution Company etc.
CPRI-Training Notes
4.8 Status of R-APDRP
A total of 30 projects (States & Union territories) with 1412 towns costing
Rs.5347.38Crores have been sanctioned and Rs.2527.30Crores of loan is disbursed under R-
APDRP Part A.
A total of 19 projects (States & Union territories) with 72towns costing Rs.1601.28Crores
have been sanctioned and Rs.424.17Crores of loan is disbursed under R-APDRP SCADA.
A total of 26 projects (States & Union territories) with 1244 towns costing
Rs.31139.48Crores have been approved and Rs.4311.58Crores of loan is disbursed under R-
APDRP Part B.
5.0 Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY)
RGGVY is a scheme of Rural Electricity Infrastructure and Household Electrification for
the attainment of the National Common Minimum Programme (NCMP) goal of providing
access to electricity to all households in five years. Rural Electrification Corporation (REC)
is the nodal agency for the programme. RGGVY was launched in April-05 by merging all
on-going schemes. Under the programme, 90% grant is provided by Government of India
and 10% as loan by REC to the State Governments.
Under the 10th
plan, a capital subsidy of Rs.5000Cr is approved for Phase I of the scheme.
5.1 RGGVY aims at: Electrifying all villages and habitations as per new definition
Providing access to electricity to all rural households
Providing electricity connection to Below Poverty Line (BPL) families free of charge.
5.2 Scope of RGGVY
Under the scheme, projects could be financed with capital subsidy for provision of:
Rural Electricity Distribution Backbone (REDB) with 33/11 KV or 66/11 KV sub-
stations of adequate capacity and lines in blocks where these do not exist
Creation of Village Electrification Infrastructure (VEI) with provision of distribution
transformers of appropriate capacity in electrified villages / habitation(s). (Habitations with
a population of above 100 for XI-Plan)
Decentralised Distributed Generation (DDG) system based on conventional&non-
conventional energy sources where grid supply is not feasible or cost-effective.
CPRI-Training Notes
5.3 Implementation Methodology and conditions:
Preparation of District based detailed project reports for execution on turnkey basis.
Involvement of central public sector undertakings of power ministry in implementation
of some projects.
Certification of electrified village by the concerned Gram Panchayat.
Deployment of franchisee for the management of rural distribution for better consumer
service and reduction in losses.
Undertaking by States for supply of electricity with minimum daily supply of 6-8 hours
of electricity in RGGVY network.
Making provision of requisite revenue subsidy by the state.
Determination of Bulk Supply Tariff (BST) for franchisee in a manner that ensures
commercial viability.
Three tier quality monitoring Mechanism for XI plan Schemes made mandatory.
Web based monitoring of progress
Release of funds linked to achievement of pre-determined milestones
Electronic transfer of funds right upto the contractor level
Notification of Rural Electrification Plans by the state governments
REDB, VEI and DDG would also cater to the requirement of agriculture and other
activities including
• irrigation pumpsets
• small and medium industries
• khadi and village industries
• cold chains
• healthcare
• education and IT
This would facilitate overall rural development, employment generation and poverty
alleviation.
5.4 Rural Household Electrification of Below Poverty Line Households:
Electrification of un-electrified Below Poverty Line (BPL) households would be financed
with 100% capital subsidy as per norms of Kutir JyothiProgramme in all rural habitations.
Households above poverty line would be paying for their connections at prescribed
connection charges and no subsidy would be available for this purpose.
CPRI-Training Notes
The over-all subsidy should be kept within 90% of the over-all project cost.
In the management of rural distribution through franchisees who could be Non-
Governmental Organisations (NGOs), Users Association, Cooperatives or individual
entrepreneurs, the Panchayat institutions would be associated. The franchisees arrangement
could be for system beyond and including feeders from substation or from and including
Distribution Transformer(s).
5.5 Franchisees :
In the management of rural distribution through franchisees who could be Non-Governmental Organisations (NGOs), Users Association, Cooperatives or individual entrepreneurs, the Panchayat institutions would be associated. The franchisees arrangement could be for system beyond and including feeders from substation or from and including Distribution Transformer(s).
5.6 Revenue Sustainability
Based on the consumer mix and the prevailing consumer tariff and likely load, the Bulk
Supply Tariff (BST) for the franchisee would be determined after ensuring commercial
viability of the franchisee. Wherever feasible, bidding may be attempted for determining the
BST. This Bulk Supply Tariff would be fully factored into the submissions of the State
Utilities to the State Electricity Regulatory Commissions (SERCs) for their revenue
requirements and tariff determination. The State Government under the Electricity Act is
required to provide the requisite revenue subsidies to the State Utilities if it would like tariff
for any category of consumers to be lower that the tariff determined by the SERC. While
administering the scheme, prior commitments may be taken from the State Government
regarding –
a) Determination of bulk supply tariff for franchisees in a manner that ensures their
commercial viability.
b) Provision of requisite revenue subsidy by the State Government to the State Utilities as
required under the Electricity Act.
5.7 The capital subsidy for eligible projects under the scheme would be given through
REC. These eligible projects shall be implemented fulfilling the conditionality‘s
indicated above. In the event the projects are not implemented satisfactorily in
accordance with the conditionality‘s indicated above, the capital subsidy could be
converted into interest bearing loans.
CPRI-Training Notes
5.8 The services of Central Public Sector Undertakings (CPSUs) have been offered to the
states for assisting them in the execution of Rural Electrification Projects as per their
willingness and requirement. With a view to augment the implementation capacities for
the programme, REC has entered into Memorandum of Understanding (MOUs) with
NTPC, POWERGRID, NHPC AND DVC to make available CPSUs‘ project
management expertise and capabilities to states wishing to use their services. This is
being operationalised through a suitable Tripartite Agreement.
5.9 Upto 1 per cent of the total subsidy under the scheme would be used for associated
works / efforts of the programme linked to research, technology development, capacity
building, information system development, awareness and other administrative and
associated expenses and undertaking of pilot studies and projects complimentary to this
rural electrification scheme.
5.91 This scheme merges the existing ―Accelerated Electrification of one lakh Villages and
one crore Households‖ and the Minimum Needs Programme for rural electrification.
6.0 RGGVY in the XI plan
Continuation of RGGVY- Scheme of Rural Electricity Infrastructure and Rural Household
Electrification has been sanctioned in the XI-Plan for attaining the goal of providing access
to electricity to all households, electrification of about 1.15lakh un-electrified villages and
electricity connections to 2.34 crore BPL households by 2009. The approval has been
accorded for capital subsidy of Rs.28000 crores during the XI-Plan period.
Unlike the RGGVY of the X-Plan where the scope of the scheme remains, the funding
mechanism will be on same pattern for 90% subsidy while 10% can be from REC or from
own funds of the state/loan from financial institutions. The Monitoring committee on
RGGVY, while sanctioning DDG projects shall coordinate with MNRE to avoid any
overlap. The provision for subsidy requirement for DDG is Rs.540crores.
REDB, VEI and DDG would indirectly facilitate power requirement of agriculture and other
activities including irrigation pump sets, small and medium industries, khadi and village
industries, cold chains, health care, education and IT etc. This would facilitate overall rural
development, employment generation and poverty alleviation.
The rate of reimbursement for providing free connections to BPL households would be
Rs.2200 per household. Households above poverty line are to pay for their connections at
prescribed connection charges and no subsidy would be available for this purpose.
Wherever SC/ST population exists among BPL households and subject to being eligible
otherwise, they will be provided connection free of cost and a separate record will be kept
CPRI-Training Notes
for such connection.
Three-Tier Monitoring Mechanism: The Quality Control Mechanism would be governed by
the Quality Control Manual prepared by REC for the Scheme.
7.0RGGVY in the XII & XIII plan
Continuation of RGGVY - Scheme of Rural Electricity Infrastructure and Rural Household
Electrification in the 12th
& 13th
plan for:
Completing spillover works of projects sanctioned in the 10th
& 11th
plan
Continuing the scheme for covering all remaining census villages and habitations
with population of above 100
Providing free electricity connections to BPL households at the rate of Rs.3000 per
connection in villages and habitations with population of above 100
Extending DDG to grid connected areas to supplement the availability of power in
areas where power supply is less than six hours a day.
The villages and habitations which have not been covered under RGGVY in 10th
& 11th
plan
projects would be eligible for consideration in 12th
plan. Besides these, villages and
habitations covered in 10th
& 11th
plan projects would also be eligible for the purpose of
covering the remaining BPL households.
CPRI-Training Notes
Progress report of village electrification as on 31.05.2014 as per 2011
Sl. No
States/ UTs
Total in habited
villages as per 2011 census
villages electrification as
on 31.03.2014 (provisional)(#)
Cumulative achieve-
ment as on 31.05.2014
%age of villages
electrified as on
31.05.2014
Un-electrified villages as
on 31.05.2014
Numbers %age
1 Andhra Pradesh 26286 26286 100 26286 100 0
2 Arunachal Pradesh 5258 3586 68.2 3586 68.2 1672
3 Assam 25372 24404 96.2 24404 96.2 968
4 Bihar 39073 37002 94.7 37316 95.5 1757
5 Chattisgarh 19567 19055 97.4 19055 97.4 512
6 Goa 320 320 100 320 100 0
7 Gujarat 17843 17843 100 17843 100 0
8 Haryana 6642 6642 100 6642 100 0
9 Himachal Pradesh 17882 17880 99.9 17880 99.99 2
10 Jammu & Kashmir 6337 6224 98.2 6224 98.2 113
11 Jharkhand 29492 27142 92 27142 92 2350
12 Karnataka 27397 26704 97.47 26704 97.5 693
13 Kerala 1017 1017 100 1017 100 0
14 Madhya Pradesh 51929 50381 97 50394 97 1535
15 Maharashtra 40956 40920 99.9 40920 99.9 36
16 Manipur 2379 2061 86.6 2061 86.6 318
17 Meghalaya 6459 5132 79.5 5132 79.5 1327
18 Mizoram 704 650 92.3 650 92.3 54
19 Nagaland 1400 1261 90.1 1261 90.1 139
20 Odisha 47677 38920 81.6 38920 81.06 8757
21 Punjab 12168 12168 100 12168 100 0
22 Rajasthan 43264 39036 90.2 39036 90.2 4228
23 Sikkim 425 425 100 425 100 0
24 Tamil Nadu 15049 15049 100 15049 100 0
25 Tripura 863 837 97 837 97 26
26 Uttar Pradesh 97813 96515 98.7 96515 98.7 1298
CPRI-Training Notes
Annexure-I
Sl. No
States/UTs
Total in habited
villages as per 2011 census
villages electrification as
on 31.03.2014 (provisional)(#)
Cumulative achieve-
ment as on 31.05.2014
%age if villages
electrified as on
31.05.2014
Un-electrified villages as
on 31.05.2014
Numbers %age
Union Territories
1 A&N Island 396 308 77.8 308 77.8 88
2 Chandigarh 5 5 100 5 100 0
3 D&N Haveli 65 65 100 65 100 0
4 Daman & Diu 19 19 100 19 100 0
5 Delhi 103 103 100 103 100 0
6 Lakshadweep 6 6 100 6 100 0
7 Pondicherry 90 90 100 90 100 0
Total (UTs) 684 596 87.1 596 87.1 88
Total 597464 571155 95.6 571482 95.7 25982
(^) villages in forest area
(#) The figures are provisional and subject to confirmation from States.
27 Uttarkhand 15745 15638 99.3 15638 99.3 107
28 West Bengal 37463 37461 99.99 37461 99.99 2
Total (States) 596780 570559 95.6 570886 95.7 25894
CPRI-Training Notes
Annexure-II
SCHEME ON RURAL ELECTRICITY INFRASTRUCTURE
AND VILLAGE ELECTRIFICATION
COST ESTIMATES OF THE SCHEME
Rs. In crore
1. Electrification of 125,000 un-electrified villages
which includes interalia development of backbone
networkcomprising Rural Electricity Distribution
Backbone (REDB)and Village Electrification
Infrastructure (VEI) and last mileservice connectivity
to 10% Households in the village @Rs. 6.50
lakh/village
8,125
2. Rural Households Electrification (RHE) of
populationunder BPL i.e. 30% of 7.8 crore. Un-
electrifiedHouseholds/ i.e. 2.34 crore households @
Rs.1500/H/H asper Kutir Jyothi dispensation
3,510
3. Augmentation of backbone network in already
electrifiedvillages having un-electrified inhabitations @
Rs./1 lakh/village for 4.62 lakh villages
4,620
Total (1 + 2 + 3) 16,255
Outlay for the scheme 16,000
Subsidy component @ 90% for items 1 & 3 and 100%
foritem 2
14,750
CPRI-Training Notes
Component of subsidy to be set aside for enabling
activities including technology development @ 1%
ofoutlay
160
Annexure -III
Status of Village Electrification as on 31.3.2004
Sl. State Total No. of Total No. of Balanc % age of
No.
inhabited villages Balance electrified
villages as per electrified
unelectifie
d villages
1991 census Unelec
villages
1 Andhra Pradesh 26586 26565 $ 100
2. Arunachal Pradesh 3649 2335 1314 64
3. Assam 24685 19081 5604 77.30
4. Bihar 38475 19251 19224 50
5. Jharkhand 29336 7641 21695 26
6. Goa 360 360 - 100
7. Gujarat 18028 17940 $ 100
8. Haryana 6759 6759 - 100
9. Himachal Pradesh 16997 16891 106 99.38
10 J&K 6477 6301 176 97.28
11. Karnataka 27066 26771 295 98.91
12. Kerala 1384 1384 - 100
13. Madhya Pradesh 51806 50474 1332 97.43
14. Chattisgarh 19720 18532 1188 94
15. Maharashtra 40412 40351 - 100
16. Manipur 2182 2043 139 93.63
17. Meghalaya 5484 3016 2468 55
18. Mizoram 698 691 7 99
CPRI-Training Notes
19. Nagaland 1216 1216 - 100
20. Orissa 46989 37663 9326 80.15
21. Punjab 12428 12428 - 100
22. Rajasthan 37889 37276 613 98.38
23. Sikkim 447 405 42 90.60
24. Tamil Nadu 15822 15822 - 100
25. Tripura 855 818 37 95.67
26. Uttar Pradesh 97122 57042 40080 58.73
27. Uttaranchal 15681 13131 2550 83.73
28. West Bengal 37910 31705 6205 83.63
Total (States) 586463 47382 11241 80.80
Total UTs 1093 1090 $ 100%
All India 587556 474982 112401 80.80%
$ Balance villages are not feasible for electrification. * As per the new definition of village electrification (effective from 2004-05) total number
of unelectrified villages is estimated to be around 1,25,000.
CPRI-Training Notes
RURAL HOUSEHOLDS ELECTRIFICATION - 2001 CENSUS
Annexure -IV
S.
No. S t a t e
Total no. Of
Rural
Households
Households
Having
Electricity
% electrified
House-holds
% un-electrified
Households
1 Andhra Pradesh 12,676,218 7,561,733 59.65 40.35
2
Arunachal
Pradesh 164,501 73,250 44.53 55.47
3 Assam 4,220,173 697,842 16.54 83.46
4 Bihar 12,660,007 649,503 5.13 94.87
5 Chhattisgarh 3,359,078 1,548,926 46.11 53.89
6 Delhi 169,528 144,948 85.50 14.50
7 Goa 140,755 130,105 92.43 7.57
8 Gujarat 5,885,961 4,244,758 72.12 27.88
9 Haryana 2,454,463 1,926,814 78.50 21.50
10 Himachal Pradesh 1,097,520 1,036,969 94.48 5.52
11
Jammu &
Kashmir 1,161,357 868,341 74.77 25.23
12 Jharkhand 3,802,412 379,987 9.99 90.01
13 Karnataka 6,675,173 4,816,913 72.16 27.84
14 Kerala 4,942,550 3,238,899 65.53 34.47
15 Madhya Pradesh 8,124,795 5,063,424 62.32 37.68
16 Maharashtra 10,993,623 7,164,057 65.17 34.83
17 Manipur 296,354 155,679 52.53 47.47
18 Meghalaya 329,678 99,762 30.26 69.74
19 Mizoram 79,362 35,028 44.14 55.86
20 Nagaland 265,334 150,929 56.88 43.12
21 Orissa 6,782,879 1,312,744 19.35 80.65
22 Punjab 2,775,462 2,482,925 89.46 10.54
23 Rajasthan 7,156,703 3,150,556 44.02 55.98
24 Sikkim 91,723 68,808 75.02 24.98
CPRI-Training Notes
Union Territories
S.
No.
Union Territory
Total no. of
Rural
Households
Households
Having
Electricity
% electrified
House-holds
% un-electrified
Households
1
A.& Nicobar
Islands 49,653 33,807 68.09 31.91
2 Chandigarh 21,302 20,750 97.41 2.59
3
D.& Nagar
Haveli 32,783 27,088 82.63 17.37
4 Daman & Diu 22,091 21,529 97.46 2.54
5 Lakshadeep 5,351 5,337 99.74 0.26
6 Pondicerry 72,199 58,486 81.01 18.99
ALL INDIA 138,271,559 60,180,685 43.52 56.48
12.0 References
[1] Ministry of Power, Government of India Website
(www.powermin.nic.in)
[2] Central Electricity Regulatory Commission Website:
(http://www.cercind.gov.in) [3] ‗Indian Power Sector: Challenge and response‘ (Book), R.V. Shahi,
25 Tamil Nadu 8,274,790 5,890,371 71.18 28.82
26 Tripura 539,680 171,357 31.75 68.25
27 Uttar Pradesh 20,590,074 4,084,288 19.84 80.16
28 Uttaranchal 1,196,157 602,255 50.35 49.65
29 West Bengal 11,161,870 2,262,517 20.27 79.73
CPRI-Training Notes
Excel Books, New Delhi, 2005
[4] Published in Gazette of India The Electricity Act, 2003. India:
Universal Law Publication Company Pvt. Ltd.
[5] ‗National Training policy for power sector’, Ministry of Power,
Government of India, New Delhi, June 2002.
[6] Central Electricity Authority of India Website (http://www.cea.nic.in). [7] ‗Modernization of power Distribution’, (Book), M.V.S. Birinchi,
National Power Training Institute, New Delhi, March 2004.
[8] Ministry of Power, APDRP website: ‗http://www.apdrp.gov.in‘
CPRI-Training Notes
BASIC PRINCIPLES OF ELECTRICAL SAFTEY & RULES
Rajashekar P. Mandi, Engineering Officer
Energy Efficiency & Renewable Energy Division, Central Power Research Institute, Bangalore, India, E-
mail:[email protected]
1.0 INTRODUCTION
Safety means the state or condition of freedom from danger or risk. Safety can also be termed as freedom of persons from injury and of property from damage. The year 1789 is of great historical importance. It saw the outbreak of French Revolution and also ushered in the era of Industrial Revolution. The philosophy of that time was that accidents are an inevitable by-product of industrialization and that worker is responsible for his own safety. However, in the year 1833, world’s first Factory’s Act was enacted in UK. It was an important milestone in the evolution of the safety. The first successful Workmen’s Compensation Law was enacted in the USA in 1911 which was another leap forward for mankind. The Factory’s Act and Workmen’s Compensation Act constitute the first phase of safety.
2.0 ELECTRICAL SAFETY
Electrical Safety is essential tools for day to day life of human beings. The electrical safety can
be ensured by conducting electrical safety audit and implementation of electrical safety audit
measures.
The Electrical safety audit (ESA) is a systematic approach to evaluate potential hazards and to
recommend suggestions for improvement. ESA is an important tool for identifying deterioration
of standards, areas of risks or vulnerability, hazards and potential accidents in plants for
determining necessary action to / minimize hazards and for ensuring that the whole safety effort
is effective & meaningful.
Although electrical hazards will be identified and assessed in general safety audits,
comprehensive electrical safety audits can provide a thorough review of the electrical system.
This could identify potential electrical hazards, flaws in design system, maintenance system, etc.
3.0 HAZARDS OF ELECTRICITY
The primary hazards associated with electricity and its use are:
a) Shock: Electric shock occurs when the human body becomes part of a path through which electrons can flow. The resulting effect on the body can be either direct or indirect.
Direct. Injury or death can occur whenever electric current flows through the human body. Currents of less than 30 mA can result in death.
CPRI-Training Notes
Indirect. Although the electric current through the human body may be well below the values required to cause noticeable injury, human reaction can result in falls from ladders or scaffolds, or movement into operating machinery. Such reaction can result in serious injury or death.
b) Burns: Burns can result when a person touches electrical wiring or equipment that is improperly used or maintained. Typically, such burn injuries occur on the hands.
c) Arc Blast: Arc-blasts occur from high-amperage currents arcing through air. This abnormal current flow (arc-blast) is initiated by contact between two energized points. This contact can be caused by persons who have an accident while working on energized components, or by equipment failure due to fatigue or abuse. Temperatures as high as 35,000 o F have been recorded in arc-blast research. The three primary hazards associated with an arc-blast are:
d) Thermal Radiation. In most cases, the radiated thermal energy is only part of the total energy available from the arc. Numerous factors, including skin color, area of skin exposed, type of clothing have an effect on the degree of injury. Proper clothing, work distances and overcurrent protection can improve the chances of curable burns.
4.0 EFFECTS OF ELECTRICITY ON THE HUMAN BODY
The effects of electric shock on the human body depend on several factors. The major factors are:
1. Current and Voltage
2. Resistance
3. Path through body
4. Duration of shock
The muscular structure of the body is also a factor in that people having less musculature and more fat typically show similar effects at lesser current values.
4.1 Current and Voltage
Although high voltage often produces massive destruction of tissue at contact locations, it is generally believed that the detrimental effects of electric shock are due to the current actually flowing through the body. Even though Ohm's law (I=E/R) applies, it is often difficult to correlate voltage with damage to the body because of the large variations in contact resistance usually present in accidents. Any electrical device used on a house wiring circuit can, under certain conditions, transmit a fatal current. Although currents greater than 10 mA are capable of producing painful to severe shock, currents between 100 and 200 mA can be lethal.
With increasing alternating current, the sensations of tingling give way to contractions of the muscles. The muscular contractions and accompanying sensations of heat increase as the current is increased. Sensations of pain develop, and voluntary control of the muscles that lie in the current pathway becomes increasingly difficult. As current approaches 15 mA, the victim cannot let go of the conductive surface being grasped. At this point, the individual is said to "freeze" to the circuit. This is frequently
CPRI-Training Notes
referred to as the "let-go" threshold. As current approaches 100 mA, ventricular fibrillation of the heart occurs. Ventricular fibrillation is defined as "very rapid uncoordinated contractions of the ventricles of the heart resulting in loss of synchronization between heartbeat and pulse beat." Once ventricular fibrillation occurs, it will continue and death will ensue within a few minutes. Use of a special device called a de-fibrillator is required to save the victim. Heavy current flow can result in severe burns and heart paralysis. If shock is of short duration, the heart stops during current passage and usually re-starts normally on current interruption, improving the victim's chances for survival.
4.2 Resistance
Studies have shown that the electrical resistance of the human body varies with the amount of moisture on the skin, the pressure applied to the contact point, and the contact area. The outer layer of skin, the epidermis, has very high resistance when dry. Wet conditions, a cut or other break in the skin will drastically reduce resistance. Shock severity increases with an increase in pressure of contact. Also, the larger the contact area, the lower the resistance.
4.3 Path through Body
The path the current takes through the body affects the degree of injury. A small current that passes from one extremity through the heart to the other extremity is capable of causing severe injury or electrocution. There have been many cases where an arm or leg was almost burned off when the extremity came in contact with electrical current and the current only flowed through a portion of the limb before it went out into the other conductor without going through the trunk of the body. Had the current gone through the trunk of the body, the person would almost surely have been electrocuted. A large number of serious electrical accidents in industry involve current flow from hands to feet. Since such a path involves both the heart and the lungs, results can be fatal.
4.4 Duration of Shock
The duration of the shock has a great bearing on the final outcome. If the shock is of short duration, it may only be a painful experience for the person. If the level of current flow reaches the approximate ventricular fibrillation threshold of 100 mA, a shock duration of a few seconds could be fatal. This is not much current when you consider that a small light duty portable electric drill draws about 30 times as much. At relatively high currents, death is inevitable if the shock is of appreciable duration; however, if the shock is of short duration, and if the heart has not been damaged, interruption of the current may be followed by a spontaneous resumption of its normal rhythmic contractions.
CPRI-Training Notes
8.0 ELECTRICAL SAFETY RULES
Some of the electrical safety rules are as follows:
1. Do not renew a blown fuse until you are satisfied as to the cause and have rectified the
irregularity.
2. Do not close any switch unless you are familiar with the circuit which it controls and know
the reason for its being open.
3. Do not work on the live circuit without the express orders of the supervisor. Make sure that
all safety precautions have been taken and you are accompanied by a second person
competent to render First Aid and Artificial Respiration.
4. Do not touch or tamper with any electrical gear or conductor unless you have made sure that
it is DEAD and EARTHED.
5. Do not disconnect earthing connections or render ineffective the safety gadgets installed on
mains and apparatus.
6. Do not open or close switch or fuse slowly or hesitatingly. Do it quickly and positively.
7. Do not use wires with poor insulation.
8. Do not touch any electrical circuit when your hands are wet or bleeding from a cut or an
abrasion
9. Do not work on energized circuit without taking extra precaution such as the use of rubber
gloves.
10. Do not disconnect a plug by pulling a flexible cable when the switch is on.
11. Do not use fire extinguisher on electrical equipment unless it is clearly marked for that
purpose. Use sand and blanket instead.
12. Do not throw water on live electrical equipment in cases of fire.
13. Do not attempt to disengage a person in contact with a live apparatus, which you cannot
switch off immediately. Insulate yourself from earth by standing on rubber mat or dry board,
before attempting to get him clear. Do not touch his body; push him clear with a piece of dry
wood.
14. Do continue artificial respiration until recovery or death certified by doctor.
15. Do not allow visitors and unauthorized person to touch or handle electrical apparatus or come
within the danger zone of HV apparatus.
16. Do not test circuit with bare fingers
17. Do not make any temporary joints in the wiring without proper insulation.
18. Do not provide fuse on neutral circuit.
19. Do not allow children to play with sockets, plugs, wires and other electrical appliances.
20. Keep all switches OFF even when no lamps are installed in the holders.
21. Fused bulb may be replaced only when switch is OFF.
22. Treat all circuits alive until they are proved to be dead.
23. All wiring works should be done through licensed wiring contractor only.
24. Take proper permit from authorized official and provide earth discharge rods on H.T. lines
before commencing work.
25. Place rubber mats in from of electrical switch boards.
CPRI-Training Notes
26. Use safety appliances, like insulated pliers, rubber hand gloves, insulated screw drivers while
working on live L.T. lines.
27. Clear all persons working, remove all earth discharge rods, before charging any L.T./H.T.
lines.
9.0 INDIAN ELECTRICITY RULES 1956
The IE Rules initially framed during 1922 and amended in 1956. This rule consists of 11 chapters and 143 rules. The extracts of IE rules are discussed below:
Rule 1: Short title and commencement
Rule 2: Definitions of the terms used in the rules
Rule 3: No person shall be authorized to operate or under take maintenance of any part or whole of a generating station of capacity 100 MW and above together with the associated sub-station unless he is adequately qualified and has successfully undergone the type of training specified in Annexure XIV of IE Rules, 1956.
Rule 4: Refers to the qualification of Inspector.
Rule 4A – Refers to appointment of officers to assist an Electrical Inspector.
Rule 4B – Refers to the qualification of the officers appointed.
Rule 5: Entry & Inspection:
Where EI has reason to believe that there is any appliance / apparatus used in generation, transformation, conversion, distribution or use of energy.
Every supplier, consumer, owner or occupier to afford all reasonable facilities. E.I. to serve any order for any test.
Rule 6: An appeal against the order of E.I. is produced under Rule 6.
Rule 7: Fee towards inspection as specified by the court.
Rule 8: In case of dispute or difference is required to be decided by an E.I., he should decide who has to remit the fee.
CPRI-Training Notes
Rules 11 to 28 pertains to License. The procedure for applying and obtaining licenses are explained in these rules
Rule 29: All electric supply lines and apparatus shall be constructed, installed, worked and maintained in such a manner as to ensure safety of personnel and property.
Rule 30: Service lines and apparatus on consumer’s premises; must be owned by the consumer and provide necessary protection.
Rule 31: Cut-out on consumer’s premises; individual cut-out for more than one consumers.
Rule 32: Identification of earthed and earthed neutral conductors and position of switches and cut outs. In the double pole switches, link should be provided instead of fuse carrier on the neutral conductor.
Rule 33: Earthed terminal on consumer's premises. Earth pits should be constructed and maintained strictly as per IS:732. The earth resistance of earth electrodes shall not exceed 5 ohms.
Rule 34: Accessibility of bare conductors; safety measures for bare conductors.
Rule 35: Danger Boards as per IS:2551 should be affixed permanently in conspicuous position on every motor, generator, transformer and other electrical equipment.
Rule 36: Handling of lines & equipments: Before handling, the same to be discharged & to ensure use of gloves, etc.
Rule 37: Supply to vehicles, cranes, etc.-
Rule 38: Cables for portable or transportable apparatus-
Rule 39: Cables protected by bituminous materials
Rule 40: Street boxes: Street boxes shall not contain gas pipes, and precautions shall be taken to prevent, as far as reasonably possible, any influx of water or gas.
Rule 41: Distinction of different circuits- The owner of every generating station, sub-station, junction-box or pillar in which there are any circuits or apparatus, whether intended for operation at different
CPRI-Training Notes
voltages or at the same voltage, shall ensure by means of indication of a permanent nature that the respective circuits are readily distinguishable from one another.
Rule 42: Accidental charge- AC & DC circuits should be charged separately and no mixing of two or more supplies.
Rule 43: Provisions applicable to protective equipment-
a) Fire protection equipment
b) First aid box
c) Gas masks
Rule 44: Refers to the instructions for restoration of persons suffering from shock. Page 4 of 18
Rule 44 A - refers to the requirement by any person to intimate the occurrence of an electrical accident within 24 hours of the knowledge of the accident and within 48 hours in writing.
First Aid and Fire Safety
Authorized person appointed under Rule 3 shall be conversant with first aid measures restoration / resuscitation etc.,
Fire buckets filled with sand shall be maintained Fire extinguishers shall be maintained and tested once in a year First aid boxes must be replenished periodically. Gas masks: 2 Nos. for every 5 MW enclosed generating station and substation transforming 5 MVA
above for use in case of fire smoke. If more than one Generator of 5 MW, two gas masks each / generator.
Rule 45: This rule requires that every person intending execution of electrical work shall have it carried out only by a licensed Electrical contractor.
Rule 46: Periodical inspection and testing of consumer's installation: Every 5 years by E.I. or any officer appointed by Govt.
Rule 47: Supplier to test the installations before connection or reconnecting. If unsatisfied, he has to serve notice to the consumer & not service it until the defects are rectified.
Rule 47: Generators
CPRI-Training Notes
A generator shall be installed with a minimum all ground clearance of 750 mm. 4 pole Change over switch (COS); with provision to break neutral. When two generators are installed clearance between two shall be min. 1.8 m Frames of generators shall be earthed. Neutral to be provided with an isolator Neutral to be earthed with two separate & distinct earth connections HV generator (above 650 V) neutral earthing by NGR or an earthing transformer. When parallel operation & neutral switches is adopted interlock to be provided. All HV generators of 100 KVA & above shall have earth fault protection. Generators of 1000 KVA & above shall be protected again E.F. or diff Cable generator to panel in conduct and the conduct earthing. Control panel earthing With clearance of 1 M in-front and 750 mm all around Provision for metering Switch fuse / breaker for control of generator First aid and fire buckets. If sub switch boards, distributions transformers fuse boards are at a distance more than 3 M
another incoming MCB control or switch fuse. Each outgoing feeder enter MCB / cut out If higher rating board is used, interlock arrangement to isolate supply to the distribution fuse board
before renewing the fuses shall be provided. Distribution fuse boards shall be from main switchboard only. Lighting and power shall be distinct. Labeling / identification marks / danger boards shall be provided. ELCB above 5 KW
DG Sets under Rate 47 A
Prior approval of E.I. Minimum ground clearance of 750 mm & 1.8 m between
> 100 KVA , Earth fault protection
> 1000 KVA REF / Diff protection or both
COS of 4 pole Neutral Isolator & Earthing
Rule 48: Precaution against leakage before serving. Supplier to check the I.R. values. For LV & MV if 500
V DC (Megger) is applied between live card and earth for 1 minute min. 1 M . If 2.5 KV supply is applied
for 1 min. the IR shall be minimum 5 M in case of HV equipment.
Rule 49: After servicing of E.I. / supplier has reason to believe the installation earth leakage which could be dangerous, he may direct the consumer to provide facility for inspection, who shall provide the facility. The installations may be disconnected on direction from E I until the leakage is plugged.
Rule 50: Supply and use of energy
CPRI-Training Notes
Transformer Installation
HT up to 999 KVA – switch with fuse. 1000 & > 1000 kVA at 11 KV - breaker. 2500 kVA at 33 KV – Breaker All EHT installation – Breaker
Down stream transformers
< 1000 KVA – Linked switch / fuse
1000 KVA & > 1000 KVA - Breaker
All transformers of 1000 KVA & above installed shall be with breaker.
All Transformers secondary with LT breaker.
Only supplier transformer < 630 KVA linked switch and fuse
> 630 breaker
Rule 50 A: M.S. Buildings – Addnl. Provision
a) All buildings which are in height of 15 M are MSB covered under R 50A b) Electrical duct –2 rising main with COS & sealing between ducts. c) 3rd point earthing. d) Fire alarm 15 M e) Fire hydrant above 24 M. f) LD Protection g) Essential load on DG h) Location of transformer in GF outside i) Main incoming at GF at conspicuous place at a height not more than 2.75 M above ground level. j) No service pipes in ducts for power. k) Fire barrier between alternate floors.
Rule 51: Provisions applicable to medium, high or extra-high voltage installations
A. Provisions applicable to medium / high / EHV installations.
a) Space of 1 M for the board in front. b) Less than 200 mm or more than 750 mm behind. c) If 750 mm behind, passage way of 1.8 Mtrs ht.
B. Supplier to ensure compliance of Rule 50, 63 & 64 before servicing any installation.
C. If supplier proposes to connect a MV installation he shall give notice of his intention to E.I
CPRI-Training Notes
D. If supplier finds any defect he shall intimate to the consumer and E.I. with reasonable time. If consumer fails – disconnection, unless inspector directs otherwise.
Rule 52: Appeal to Inspector in regard to defects
Provision for consumer to appeal against the direction of disconnection of defeat by the supplier. Supplier shall not disconnect if directed by E.I. Reconnection within 24 hrs if disconnected.
Rule 53: Cost of inspection and test of consumer’s installation
Rule 54: Declared voltage of supply to consumer
Voltage Variation
LV ±6 %, HV + 6 % and – 9 %,
EHV + 10 % & - 12.5 %
Rule 55: Declared frequency of supply to consumer Frequency Variation: ±3%,
Rule 56: Supplier to provide seal and no one to break it
Rule 57: Meters in consumers premises :
a) All meters shall be within ±3 % accuracy b) EHV ±1 % c) Supplier to maintain equipments as approved by E.I. d) Supplier shall test all meters at intervals as directed by the Govt. e) Maintain the results of tests for examination by E.I. f) When supplier fails to test or keep records E.I. to test & seal the meters.
Rule 58: Point of commencement of supply
Rule 59: Precautions against failure of supply: Notice of failures:
a) Supplier to send notice of failure of supply. b) If the consumer not able to rectify the defects, E.I. directs disconnection
Rule 60: Test for resistance of insulation
Rule 61: a) Earthing of Neutral and body.
CPRI-Training Notes
b) Frame of motor generator to be provided earth.
Rule 61 A: Above 5 KW load, all installation with ELCB
Rule 62: System at medium voltage; earth to any conductor voltage must be less than low voltage
Rule 63: Supplier to await approvals of E.I. before putting HT/EHT into service.
Rule 64: Requirements of HT / EHT
All equipment in a separate room and inaccessible except to authorised person. All operations to be carried out by D.P
* Highest system voltage Safe working clearance
12 KV 2.6 Mtrs
36 KV 2.8 Mtrs
72.5 KV 3.1 Mtrs
145 KV 3.7 Mtrs
245 KV 4.5 Mtrs
420 KV 6.4 Mtrs
800 KV 10.3 Mtrs
Rule 64: Requirements of HT / EHT
Substation or switch station with more than 2000 ltrs (oil capacity) shall not be located in the basement.
Where sub station or switch station having more than 2000 lts either indoor or outdoor, following :
a) Baffle wall of 4 hours fire rating b/w apparatus b) Provision for soak pit
If more than 9000 lts
Draining arrangement. Authorised person to maintain records Only dry type transformer to be used inside the residential / Commercial building. Adequate fire protection arrangement to quench fuel.
If substation / switch station is in the basement , following :
Room to be at 1st basement at periphery of basement Entrance to room with fire resisting door of 2 Hr rating.
CPRI-Training Notes
Curb (sill) to prevent the flow of oil Direct access to the transformer room from outside Fire fighters BCF / BTN Oil filled transformers not above ground or below 1st basement Cable trenches to be filled with pebbles non inflammable material etc., EHV apparatus to be provided with LA protection as well as switching over voltages
Rule 64A: Additional provisions for use of energy at HV / EHV
Interlocks b/w isolators and circuit breakers. Earthing switches to be closed only when isolator is open Parallel transformer to have facility of tripping of secondary breaker when primary breaker trips Capacitor Bank doors to have interlock Protective device of C./E.F/Prot > 1000 KV Diff. protection above 10 MVA
Rule 65: Testing, Operation and Maintenance
Manufacturer’s test certificates shall be produced for all the routine tests as per ISI. No new HV or EHV apparatus, cable or supply line shall be commissioned with relevant standards All apparatus, cables and supply lines shall be maintained in healthy conditions , tests shall be
carried out and records keeping Responsibility of the owner of all HV and EHV installations
Rule 66: Metal sheathed electric supply lines. Precautions against excess leakage
Rule 67: Connection with earth – proper connection and resistance values. Neutral earthing and voltage between neutral and earth conductors
Rule 68: General conditions as to transformation and control of energy
Voltage step down sub-station where energy at high or extra-high voltage is transformed, converted, regulated or otherwise controlled in sub-stations or switch-stations
Rule 69: Pole type sub-stations- Where platform type construction is used for a pole type sub-station and sufficient space for a person to stand on the platform is provided a substantial hand rail shall be built around the said platform and if the hand rail is of metal, it shall be connected with earth.
Rule 70: Condensers- Suitable provision shall be made for immediate and automatic discharge of every static condenser on disconnection of supply.
Rule 71: Additional provisions for supply to high voltage luminous tube sign installation (Neon signs)
All live parts of the installation shall be inaccessible to unauthorised persons
CPRI-Training Notes
No part of any conductor of such circuit shall be in metallic connection with any conductor of the supply system or with the primary winding of the transformer.
All live parts of an exterior installation shall be so disposed as to protect them against the effects of the weather and fire.
The secondary circuit shall be permanently earthed at the transformer and the core of every transformer shall be earthed.
A special “caution” notice shall be affixed in a conspicuous place on the door of every high voltage enclosure
When static condenser is used the same shall be used on low voltage side and provision to discharge when supply in cut off.
Rule 72: Additional provisions for supply to high voltage electrode boilers:
Earthing of metal sheathing and metallic armouring (if any) of the high voltage boiler. Shall be controlled by a suitable circuit-breaker with an inverse time element device The owner or user of any high or extra-high voltage electrode boiler shall not bring the same into
use without giving the Inspector not less than 14 days’ notice in writing of his intention so to do.
Rule 73: Supply to X-ray and high frequency installation-
Mechanical barrier to prevent access to HV parts X-Ray tubes shall be mounted in metal enclosure which is earthed ELCB on low voltage side to detect leakage Railing platform earthing EHV generator operating at 300 KV or more shall be in a separate room, with door interlock to be
open unless the door is locked.
Rule 74: Material and strength
All OH Conductor shall have breaking strength if not less than 350 Kgs. In a low voltage consumer installations outer 15 Mtrs span length, the breaking strength could be
not less than 150 Kgs.
Rule 75:
Not more than 2 joints in a span Joints to have 95 % of the strength of a conductor
Rule 76: Maximum stresses: Factors of safety-
Owner of every OH line shall ensure the following factor of safety :
For metal – support : 1.5 For Mechanical processed concrete support : 2.0 For hand mould concrete support : 2.5 For wood support : 3.0
CPRI-Training Notes
Rule 77: Clearance above ground of the lowest conductor-
Sl. No.
Clearances Low & MV
HV Above 11 kV
1 Anywhere other than along or across
4.6 4.6 5.2
2 Along 5.5 5.8 -
3 Across 5.8 6.1 -
For EHV lines – 0.3 Mtrs for every 33 KV & Part there off.
Rule 78: Clearance between conductors and trolley wires-
Low and medium voltage lines : 1.2 m High voltage lines up to and including 11 kV : 1.8 m High voltage lines above 11 kV: 2.5 m Extra-high voltage lines: 3.0 m
Rule 79: Clearances from buildings of low and medium voltage lines and service lines-
For any flat roof, open balcony, verandah roof and lean-to-roof-
When the line passes above the building a vertical clearance of 2.5 m from the highest point When the line passes adjacent to the building a horizontal clearance of 1.2 m from the nearest point
For patched roof-
When the line passes above the building a vertical clearance of 2.5 m immediately under the lines When the line passes adjacent to the building a horizontal clearance of 1.2 m.
Rule 80: Clearances from buildings of high and extra-high voltage lines-
Where a high or extra-high voltage overhead line passes above or adjacent to any building or part of a building
(a) For high voltage lines upto and including 33 kV: 3.7 m (b) For extra-high voltage lines: 3.7 m plus 0.30 m for every additional 33 kV or part thereof.
The horizontal clearance between the nearest conductor and any part of such building shall
CPRI-Training Notes
(a) For high voltage lines upto and including 11 kV: 1.2 m (b) For high voltage lines above 11 kV – 33 kV: 2.0 m (c) For extra-high voltage lines: 2.0 m plus 0.30 m for every additional 33 kV or part thereof.
Rule 81: Conductors at different voltages on same supports-
Rule 82: Erection of / alteration of buildings.
Structures flood banks and elevation of roads. Any person / contractor is to give notice to the supplier and E.I. with drawings. Supplier has to verify and estimate. Person to remit the estimate amount Dispute regarding estimate or cost to E.I. for decision. No further work until E.I. certifies. Supplier to execute within one month from the date of deposit or as allowed by the E.I.
Rule 84: Routes: Proximity to aerodromes- Overhead lines shall not be erected in the vicinity of aerodromes until the aerodrome authorities have approved in writing the route of the proposed lines.
Rule 85: Maximum interval between supports- All conductors shall be attached to supports at intervals not exceeding the safe limits based on the ultimate tensile strength of the conductor and the factor of safety prescribed in Rule 76.
Rule 86: Conditions to apply where telecommunication lines and power lines are carried on same supports-
Every overhead telecommunication line erected on supports carrying a power line shall consist of conductors and proper guard wire.
Where a telecommunication line is erected on supports carrying a high or extra-high voltage power line arrangement shall be made to safeguard persons.
Rule 87: Lines crossing or approaching each other-
Minimum clearances in metre between lines crossing each other
Sl. No.
Nominal System Voltage
11 – 66 kV
110 –
132 kV
220 kV
400 kV
800 kV
1 Low & Medium
2.44 3.05 4.58 5.49 7.94
2 11 – 66 2.44 3.05 4.58 5.49 7.94
CPRI-Training Notes
kV
3 110 – 132 kV
3.05 3.05 4.58 5.49 7.94
4 220 kV 4.58 4.58 4.58 5.49 7.94
5 400 kV 5.49 5.49 5.49 5.49 7.94
6 800 kV 7.94 7.94 7.94 7.94 7.94
Rule 88: Guarding-
Every guard-wire shall be connected with earth at each point at which its electrical continuity is broken.
Rule 89: Service-lines from Overhead lines- No Service-line or tapping shall be taken off an overhead line except at a point of support.
Rule 90: Earthing-
Rule 91: Safety and protective devices-
Rule 92: Protection against lightning-
Rule 93: Unused overhead lines-
Rules 94 – 108: Electric traction
Rules 109 – 132: Additional Precautions to be adopted in mines and oil fields
Rule 133: Relaxation by Government-
Rule 134: Relaxation by Inspector
Rule 135: Supply and use of energy by non-licensees and others-
Rule 136: Responsibility of Agents and Managers
CPRI-Training Notes
Rule 137: Mode of entry-
Rule 138: Penalty for breaking seal- Rs. 200/- as penalty
Rule 139: Penalty for breach of Rule 45-
Rule 140: Penalty for breach of Rule 82- Person / Contractor deemed to have committed the breach.
Rule 141: Penalty for breach of Rules- Any person other than an Inspector or any officer appointed to assist the Inspector who being responsible for the observance of any of these rules commits a breach thereof, shall be punishable for every such breach with fine which may extend to Rs. 300/-
Rule 142: Application of rules- these rules shall be binding on all persons, companies and undertakings to whom licenses have been granted or with whom agreements have been made with the sanction of Govt. supply or use of electricity.
Rule 143: Repeal- The Indian Electricity Rules, 1937, are hereby repealed.
10.0 CONCLUSIONS
The electrical safety is very essential in work every part of life. Safety is team work and is every ones responsibility. The organization or employer will provide the facilities to the employees but responsibility of safety lies with individual. The overconfidence will kill the people. Use of proper insulated tools, proper joints, use of appropriate MCBs, RCCBs, Fuses, Relays, standard electrical appliances, following the safety norms, working with the presence of mind will help in reducing the accidents.
CPRI-Training Notes
ELECTRICAL SAFTEY EQUIPMENTS, PROCEDURES FOR
LINE CLEARANCE AND SAFE WORKING PROCEDURES
Rajashekar P. Mandi, Engineering Officer
Energy Efficiency & Renewable Energy Division,
Central Power Research Institute, Bangalore, India,
E-mail:[email protected]
1.0 INTRODUCTION
Electrical energy is the most commonly used form of energy because it is a rich form of energy. One cannot imagine the life without electricity in modern society. Using electricity is very simple, but, little does one know about how electricity really works. Such a situation is not good because electricity is a good servant but a very bad master. It can cause instantaneous death, lifelong disability due to severe burns or devastating fires turning crores of rupees worth assets to ashes.
It is, therefore, absolutely essential that one should know what precautions to take while using electricity.
To overcome all these safety problems, Indian Government, introduced lot of electrical safety norms in Indian Electricity Rule 1956 and amended in the Indian Electricity Act 2003.
The major objective of a safety audit / procedure is to determine the effectiveness of the company‘s
safety and loss prevention measures. It is an essential requirement of an audit system that it should
originate with the policy-making executive and a consensus should be arrived at regarding the safety
audit and its objectives.
Factories Act, 1948 (Section 7A) makes the occupier responsible for providing a safe working
environment for the employees. Safety audit is one method of evaluating the safe environment provided
in the plant, although safety audit is not a direct requirement by Factories Act. Considering the changing
international legislature trends, safety audits could become mandatory in India too in the near future.
Our experience shows that either the top management or the electrical department initiates ESAs and not
the safety department. The reason could be the lack of in depth knowledge of safety officers in electrical
aspects coupled with their limited involvement in electrical department‘s day-to-day functions.
Although electrical hazards will be identified and assessed in general safety audits, comprehensive
electrical safety audits can provide a thorough review of the electrical system. This could identify
potential electrical hazards, flaws in design system, maintenance system, etc.
CPRI-Training Notes
2.0 ELECTRICAL SAFETY EQUIPMENT
The following items of Personnel Protective Equipment (PPE) are to be worn by all personnel, at all times whilst working in on power station sites, irrespective of whether electrical related hazards are present in the tasks that are being undertaken:
safety helmet,
long sleeved high visibility (day visibility) shirt (100% cotton – 185 g/m2 ),
long pants (100 % cotton - 185 g/m2),
safety footwear,
safety glasses in and around plant, and designated workshop areas,
ear plugs/muffs in designated hearing protection areas.
Personal protective equipment (PPE) additional to the items listed above is to be used and selected in accordance for the activity. Working near energized exposed parts requires specialized PPE to be worn. Protective clothing worn by electrical workers when working live and/or others in proximity to exposed energized conductors shall be appropriate for the purpose, fit correctly and be in good condition while the work is being performed. To protect personnel from electrical hazards, each Power Station is to provide a supply of personal protective equipment that is maintained and tested in accordance with the National Standards.
Personnel required to wear items of PPE are not to modify, damage or use PPE in a way contrary to manufacturer’s instructions or the training provided for that particular item of PPE. Items of PPE that are defective or out of test date are to be immediately withdrawn from service and tagged as out of service, until repaired and/or tested by a competent person. During the performance of live electrical work, testing de-energized, fault finding or when in close proximity to energized exposed parts, personnel are not to wear or carry conductive items such as pens, mobile phones, radios, tools (unless suitably insulated), metal belt buckles, buttons, chains, studs, jewelry, body piercing, metal rimmed glasses, bracelets, rings, neck chains, exposed metal zips, watches, etc.
When working live, testing to prove de-energized, fault finding, commissioning, as a safety observer or in proximity to energized conductors electrical workers and others are to wear suitable flame retardant/arc flash protective clothing.
Arc flash energies are to be managed for electrical work and the selection of correct PPE is to be addressed based on the identified arc flash energies (ATPV) for the electrical equipment being isolated, tested or worked on. Other measures to control the risk may include working at a greater distance from the incident arc source, using longer handles to rack out equipment, using remote isolation or test equipment and modifying protection settings by engineering to reduce the arc flash potential energy.
CPRI-Training Notes
3.0 SAFETY PROCEDURES AND ACCIDENT PREVENTION
Accident can be defined as an unexpected or unforeseen occurrence and course of employment of a person resulting in an injury/damage to the persons/equipment or may not cause any such damage.
3.1 Earthing
Majority of electrical accidents are electrocution. One of the main causes of electrocution is improper earthing. Therefore, a proper attention to earthing can help in preventing majority of electrical accidents. Most of the fatal accidents are also due to electrocution.
Proper earthing is necessary to ensure safety of personnel as well as equipment.
3.2 Causes of Accidents
The causes of accidents may be broadly divided into following two categories:
3.2.1 Direct causes.
a) Unsafe Act: Violation from the commonly accepted safe procedures of the work is called Unsafe Act. b) Unsafe condition: The conditions with potential of causing injury to a person or damage to equipment are
called Unsafe Conditions.
3.2.2 Indirect Causes.
a) Lack of knowledge and skill. Incorrect knowledge Incomplete knowledge. Unskilled/low degree of skill. Misunderstanding job instructions.
b) Improper Physiological/ Anatomical characteristics. This relates to persons of:- Poor eye-sight. Hard of hearing. Over-age. Ill Allergic.
c) Improper Psychological Characteristics. Persons who are: Arrogant.
CPRI-Training Notes
Lazy. Fearful. Nervous. Egoistical. Absent-minded. Over-confident.
4.0 UNSAFE ACTS
Generally there are two types of unsafe acts
1. Know better with over confident 2. Without knowing
4.1 Some of the unsafe acts are
1. Failure to de-energize the circuit or switch off the circuit, 2. Lockout & tag out hazardous during maintenance, repair or inspection work may be due to over confident or
due to urgency. 3. Use of defective and unsafe tools. 4. Use of tools or equipment too close to energized parts or live parts. 5. Not discharging stored energy in capacitors while doing maintenance. This may give high electrical shock
due to charge stored in capacitor banks. 6. Using 3-wire cord with a 2-wire plug without using earth. 7. Using the jointed electrical cord to raise or lower equipment. 8. Overloading outlets with too many appliances. 9. Not verifying or ensuring power is put-off while taking of maintenance work. 10. Removing the third pin (ground pin) to make a 3-pin plug fit a 2-pin outlet. 11. Working in an elevated position near overhead live lines.
4.2 Hazardous environment
1. Flammable vapours, liquids and gasses 2. Combustible dusts or cotton waste 3. Poor housekeeping: blocked electrical boxes, flammable materials stored in equipment rooms, lack of
proper hazard signs 4. Corrosive atmospheres 5. Explosive environments 6. Special care is also need in wet or damp locations – water and electricity are a bad combination. If the wire
is frayed or damaged, a fatal electrical shock can result.
CPRI-Training Notes
4.3 Some common causes of unsafe equipment
1. Loose connection 2. Faulty insulation 3. Improper grounding (removal of 3rd pin) 4. Use of “homemade” extension cords 5. Defective parts 6. Unguarded love parts- -for example: 7. Bare conductors or exposed terminals
4.4 Risk Assessment
1. Identification and location of hazardous 2. Whether the Hazardous is harmful to any body 3. Assess the risk arising from Hazards 4. Decide whether the precautions are alright 5. Record the significant findings 6. Review the situation periodically and necessary action
4.5 Aggravating the risk of hazards
1. Wet surrounding 2. Water clogging 3. Grass around the electrical equipments in Sub-station 4. Water leakages on equipments 5. Cramped spaces
5.0 BEST PRACTICES
Some of the best practices to minimize the hazards are
1. Provide better illumination and ventilation system 2. Use of copper lugs for end terminations and cable glands for the cable terminations. 3. All the cable glands and panel boards have to be provided with earths. 4. Transformer must be provided with two separate earths for body and two earths for neutral grounding.
The earth pits must be monitored on regular basis. The char coal & salt are to be put on bi-annually basis. 5. The lightning arrestor of appropriate size may be installed for transformers. 6. The over current relay (OCR), under voltage relay (UVR) and earth fault relay are to be provided and are to
be tested annually. 7. The load factor of transformer must be maintained within 40 – 60 % and not to overload the transformers 8. The transformer winding temperature must be maintained below 55oC over the ambient and oil
temperature less than 50oC over ambient temperature. 9. The transformer oil is to be tested annually for healthiness of transformer.
CPRI-Training Notes
10. The condition of silica gel must be blue in colour. 11. The grass in transformer yard and sub-station must be cleared and stone jellies have to be spread in yard. 12. Maintaining earth resistance to minimum (i.e., 2 – 10 ohm) 13. Providing earthing to all equipment 14. Use of standard Electrical equipments confirming to IS standards 15. Periodic preventive maintenance 16. The cables must be laid in the cable trays or trench with proper identification. 17. The safety chart must displayed at the main entrance. 18. First aid box must be provided at main electrical room. 19. The list of operators may be displayed at the electrical room. 20. The log books for main incoming, DG sets and UPS are to be maintained. 21. At all the LDBs, UDBs, AC panels and UPS panels have to be provided with Danger Notice Board as per IE
rule 35. 22. Panel board identification name boards must be provided on all the panels. 23. For DG sets two separate earths must be provided for body and neutral. 24. For DG sets, the sound proof enclosures are to be provided. 25. Earth fault protections as per IE Rule 47 A are to be provided. 26. Use of separate 3-pin sockets of appropriate rating for individual appliances 27. Avoid use of multi point sockets for electrical appliance. 28. Use of proper sized MCBs or fuses in the circuit. 29. Proper end terminations 30. Use of lock out tags during maintenance work 31. Removing fuse and keeping safely during maintenance work. 32. Safety Chart in sub-station and at important places 33. Single line diagram of electrical system 34. Identification of feeders including cable size, MCB rating, etc. 35. Rubber mats in-front of panels 36. Earthing of all electrical panels and cable glands 37. Maintaining the proper clearances in-front and back of panels as per IE rule 38. Updating the drawings periodically 39. Use of correct size fuse and record keeping 40. Display of names of maintenance staff at sub-station or electrical room
6.0 ELECTRICAL SAFETY GUIDELINES
6.1 Transformers
Some of the safety guidelines for transformers are:
a) The transformers must be provided with two separate earths for transformer body and two earths for neutral grounding. The earth pits must be marked, clean all the earth pits regularly. The sand and char coal must be filled till the cup of earth pipe. The cup should be visible and the joint also should be visible. The water has to be put in pipe to reduce the earth resistance.
b) Lightning arrestors of appropriate size may be installed for transformers. c) The over current relay (OCR), under voltage relay (UVR) and earth fault relay are to be installed and
monitored regularly.
CPRI-Training Notes
d) Sharp edged blue jelly or pebbles may be spread at transformer bottom. e) The load factor of transformers must be maintained in the range of 40 – 60 % for better operation. f) The cables must be laid properly in the cable trench and markings must be made. g) The transformer body temperatures must be monitored at regular intervals and maintained in the range of
40 – 60 oC. h) The transformer winding and oil temperature gauges must be maintained in good condition. i) The transformer oil has to be got tested from a standard lab to ascertain the oil quality. j) The condition of silica gel must be blue in colour. If it becomes white, it has to be replaced.
6.2 Cables, panel boards and electrical room
Some of the safety guidelines for cables, panel boards & electrical room are:
a) All the cables must be terminated with proper lugs and cable glands. b) The cable glands and panel boards have to be properly earthed. c) At all panels, the cable identification, size, number of runs, etc must be marked for easy identification. d) The end termination joint temperature must be measured by using noncontact type temperature
indicators. e) The cable loading must be maintained below 60 % for better operation. Refer Table 1 for cable rating.
Table 2 gives rating of Electrical equipment and its accessories. Table 3 gives the selection of tinned copper fuse wire (as per IEE Regulations 12th Edition 1950 table 21). Table 4 gives the current ratings of rectangular copper bus bars.
f) The cables must be laid in the cable trays. g) The safety chart is to be displayed at the main entrance. h) First aid box is to be provided at main electrical room. i) The list of operators, linemen, supervisor, etc must be displayed at the electrical room. j) The log books have to be maintained at main electrical room. The log book can contain incoming voltage,
current, power factor and energy meter reading for both the incomings. k) At all the LDBs, UDBs, AC panels and UPS panels have to be provided with Danger Notice Board as per IE
rule 35. l) Panel board identification name boards must be provided on all the panels.
6.3 Diesel Generator Sets
Some of the safety guidelines for DG sets are:
a) For each DG set two separate earths must be provided for body and neutral. b) For both the DG sets, the sound proof enclosures must be provided. c) These DG sets must start automatically whenever the power failure through AMF panels. d) The sufficient illumination level and ventilation must be provided in DG room. e) Earth fault protections as per IE Rule 47 A are provided but are bypassed. These earth fault relays have to
be taken in the circuit.
CPRI-Training Notes
6.4 Motors and lift
Some of the safety guidelines for motors & lifts are:
a) The lift motor body must be earthed. b) Limit switches must be in service in the lift. c) Telephone must be provided inside the lift and important five emergency numbers must be displayed. d) Power and lighting circuits must be maintained separately. e) Buffers springs must be in good condition. f) Lighting level must be good inside the lift. g) Exhaust fan must be provided in the lift. h) Earthing must be provided for all DBs.
7.0 PERMIT SYSTEM IN SUB-STATION
7.1 Procedure for permit to work (line clear)
Line clear is a permit to work Issued by a authorized person to a authorized person only. More than one gang under the same supervisor working simultaneously – separate line clear for each gang Line clear is required by self, he can take selfline clear by following the same procedure & precautions. Line clear book is very important document. Pages must be numbered and pages should not be used for other purpose or teared-off If any page is missing, the custodian will be responsible and attest his signature with date and reason of
missing of page. Line clear book shall be reviewed by the Higher officials like Asstt. Executive Engineer or equivalent Line clear can also be issued / received over telephone. But it is desirable that the issuer / receiver recognizes each other’s voice. A secret code number shall be followed in such cases
7.2 Procedure before issue of line clear
Approval of the competent authority for shut-down of line/equipment should be verified Line/equipment shall be switched off No back feed certificates, wherever necessary shall be obtained The issuer must be ensured that the breaker / GOS are opened and breaker panel is locked The line/equipment is earthed by discharge rods A ‘Danger Do not operate’ or ‘ Men on line’ board shall be exhibited All operations for issue of line clear shall be done personally by the issuer or it shall be done under his
personal supervision. After following all the precautions the line clear book shall be filled up and signed with date & time by the
issuer and receiver.
7.3 Responsibilities of receiver
Receiver should indicate the specific equipment/line which he wants to work when requisitioning for L.C.
CPRI-Training Notes
If the receiver is at the same place as that of the issuer he shall follow all the operations being conducted so as to ensure that line clears are being issued on the correct line/equipment.
At the work spot, after receiving line clear, he shall earth the line/equipment on either side of the workspot ( in case of line sending end & receiving end)
In case if any other power lines are crossing near to work spot of the line on which LC is received he shall also obtain LCs on all such lines to avoid induction.
He shall write down on the duplicate form the number of persons engaged on the work.
7.4 Rules followed while returning LC
Persons who have received the LC only return it. He shall personally ensure that there are no men, material or earth on the line He shall inform all the workmen that it is no longer safer to work on the line as the line clear is being
returned Line/equipment shall not be charged until the LC is cancelled
7.5 Precautions before cancel LC
Returned LC shall be carefully examined. It shall be ensured that all the certificates required are furnished ‘Men on line’ or ‘Danger do not operate’ boards shall be removed It shall be ensured that no other LC is pending. All men material removed.
Earthing is removed All no back fed certificates shall be returned After charging the line/equipment check should be made for unusual sound/noise All the workmen/supervisor shall be permitted to leave the work spot only after the normalcy is restored.
8.0 RECOVERY AND RESUSCITATION
There are scientifically approved methods to resurrect a person who met with an electrical accident.
8.1 Neilsen’s Method
Position 1
Place the victim face downwards with his arms folded one over the other and the head resting on them.
Kneel at the victim’s head on one or both knees. Place your hands on the back of the victim away from the armpits with your fingers spread out downwards and thumbs touching each other.
CPRI-Training Notes
Position 2
As you count one, two, three, rock forward, keeping arms straight until they are nearly vertical thus steadily pressing the victim’s back. This completes expiration.
Position 3
As you proceed to count four, rock backwards releasing pressure and slide your hands downwards along the victim’s arms and grasp his upper arm just above the elbows. Continue to rock backwards.
Position 4
As you rock back counting five, six, seven, raise and pull the victim’s arm towards you until you feel tension in his shoulders. This expands his chest and results in inspiration.
CPRI-Training Notes
As you count eight, lower the victim’s arms and move your hands up for the initial position. Repeat this cycle twelve times a minute. When the victim starts breathing, synchronize your steps with his breathing until he breathes strongly. Then stop.
8.2 Schafer’s Method
Lay the patient on his stomach one arm extended directly overhead the other arm bent at elbow and with the face turned outward and resting on hand and forearm so that the nose and mouth are free for breathing. Kneel over the patient, rest the hands flat on the small of his back with fingers resting on the ribs, the little finger just touching the lowest rib with the thumb and other fingers in a natural position and the tips of the fingers just out of sight.
With arms straight swing forward slowly and gently over the patient so that the weight of your body is gradually brought to bear on the patient exerting a steady pressure downward. The shoulder should be directly over the heel of the hand at the end of the forward swing. Do not bend your elbows.
yourself gently backwards so as to completely remove the pressure
After two seconds, swing forward again. Continue these two movements twelve to fifteen times a minute. The object is to keep expanding and contracting the casualty’s lungs so as to initiate slow breathing.
8.3 Silvester‟s Method
CPRI-Training Notes
The patient is laid on his back. His arms are grasped above the wrists and drawn first upward and then above the head until they touch the floor.
Bring back the arms to the chest and exert pressure in a downward direction.
The tongue is to be pulled out and held in that position so that it does not obstruct the throat. Otherwise a large thick pad may be placed behind the shoulders, so that the head lies dangling downwards and the tongue does not obstruct.
8.4 Artificial Respiration
9.0REPORTING
The procedure for reporting an occurrence of accidents shall be laid down. Example…
• Dept. / Non dept.
• Fatal / non fatal
• Preliminary investigation report – 5 days (DE)
• Detailed investigation report – 15 days (DE)
• Remarks on investigation report – 30 days (SE)
Immediate to superior
next higher superior
CPRI-Training Notes
• Compensation payable
There shall be standard formats for reporting, guidelines for investigation and fixing responsibility for accident. The investigation reports shall clearly indicate the measures for avoiding recurrence of such accidents.
10.0 CONCLUSIONS
The electrical safety is very essential in work every part of life. Safety is team work and is every ones responsibility. The organization or employer will provide the facilities to the employees but responsibility of safety lies with individual. The overconfidence will kill the people. Use of proper insulated tools, proper joints, use of appropriate MCBs, RCCBs, Fuses, Relays, standard electrical appliances, following the safety norms, working with the presence of mind will help in reducing the accidents.
CPRI-Training Notes
POWER QUALITY ISSUES, MEASUREMENTS AND MITIGATION
Rajashekar P. Mandi, Engineering Officer
Energy Efficiency & Renewable Energy Division,
Central Power Research Institute, Bangalore, India,
E-mail:[email protected]
1.0 INTRODUCTION
With the use of modern high-tech microprocessor based technology in industries for various applications, the power quality is being polluted. To produce the quality of products, the power supply should be of high quality. The power electronic based equipment will present a non-linear load characteristic to the network and producing the harmonics in the system. The harmonic currents increase the RMS value of the current and create the neutral current to circulate in the distribution network. The presence of harmonics decrease the distribution capacity and increase the losses.
The voltage sags, swells and surges affect the performance of the equipment. Voltage unbalance between three phases created by the unbalanced loading on 3-phases will reduce the motor efficiency and rating.
The use of power conditioning equipment will reduce the harmonic distortions, voltage unbalance, power factor corrections, etc..
This paper presents the affect of power quality on the equipment and increased losses in the distribution system. The power quality issues are discussed in detail.
2.0 POWER SUPPLY ISSUES
The utility had to supply the good quality of power supply to the consumer with allowable limits of voltage and frequency variation, voltage harmonics, etc. But due to the increased gap between supply and demand and more and more usage of power electronic equipment, the power quality is being polluted. Various power quality issues are discussed below.
2.1 Voltage variation
In industries, the incoming voltage variation band is very high compared to the developed countries. Since the transformers in industries are of off-load tap changers, the required voltage cannot be met adequately.
CPRI-Training Notes
To overcome the voltage variation, on-load tap changers for transformers may be used for incoming voltage levels above 66 kV. For the voltage below 66 kV, the OLTC is not economically feasible. The use of regulating transformers will improve the voltage quality, the techno-economics are attractive for large scale industries. The use of voltage stabilizers in LT side is also proves to be economical in some instances where the voltage dip is more than 10 % of rated voltage. The use of captive generation (DG sets) during peak hours (for low voltage) also proves to be economical.
2.2 Voltage sags and swells
The voltage sags are being created by switching transient of heavy loads. The voltage sag can occur in one phase or in all the 3-phases based on the switching and type of the equipment. Generally, the voltage sags will last for 100 to 500 ms and dip by about 30 % [1]. If the sag sustains more than this values corrective action may be taken.
When the capacitor banks are directly charged, the inrush current will be in the range between 7 to 9 times of the normal current which will create the transients. This can be avoided by installing the series reactor in phase or in neutral conductor.
The voltage surge and swells are being created by switching off certain heavy equipment.
The voltage sags, swells and surges can be mitigated by the use of surge arrestors and uninterrupted power supply units which will inject the voltage whenever voltage sag takes place and control the voltage during surge and swell.
The earth current developed in the equipment due to the voltage drop between the equipment and true earth. This noise voltage will be significant compared with the signal voltages. The computer hardware is designed to minimize sensitivity to this kind of disturbance but it cannot be eliminated entirely. The earth reference plane of different computers on different floors will be no longer at the same potential. Currents will flow along the shields of data cables connected to earth at both ends for EMC compliance.
Short duration voltage changes, resulting from switching, short-circuits and load changing can result in light flicker. The excessive flicker can cause migraine and is responsible for some instances of the so called ‘sick building syndrome’.
2.3 Voltage unbalance
The voltage unbalance between 3-phases is caused by load unbalance, dissimilar voltage drops in distribution equipment and different power factors in three phases. The voltage unbalance will cause negative sequence current in the motor winding which will increase the motor loss and the negative sequence current will create the
CPRI-Training Notes
negative sequence torque which will oppose the normal torque. This negative sequence torque will reduce the motor capacity. Figure 1 gives the variation of computed increased losses for 18.5 kW motor. The total losses are as high as 33 % at voltage unbalance of 5 %. The motor capacity will reduce 75 % at a voltage unbalance of 5 % as per the IEEE standard.
The voltage unbalance at the motor terminal can be overcome by the use of active line conditioner [2]. In this case voltage unbalance is achieved by injecting a correcting voltage in the phases. The magnitude of the injecting voltage is computed by evaluating the negative sequence voltage, which will become the input to the PWM inverter.
2.4 Harmonics Distortion
The power electronics
technology
based equipment
like compu
ters, electr
onic ballast
s, variabl
e speed
drives, arc
furnaces
etc., draw the non-sinusoidal current from the utility and distort the utility voltage waveforms, which will break the empirical relationship between the peak and Root Mean Square (RMS) value (i.e. RMS value of pure sine wave is
1/2 times of its peak value). The distorted non-sinusoidal currents are built up of sinusoidal currents of different frequencies and of various magnitudes. These currents are termed as harmonics. These harmonics are expressed as Total harmonic distortion (THD). The THD is the ratio of the root mean square of the harmonic contents to the root mean square value of the fundamental 50 Hz signal. THD is expressed as a percentage and is computed as:
100*lfundamentaofamplitudeofSquare
harmonicsofamplitudesofsquaresofSumTHD
Figure 1: Variation of motor current and losses with
voltage unbalance at motor terminals.
0
5
10
15
20
25
30
35
0.0 1.0 2.0 3.0 4.0 5.0
Voltage unbalance, %
Incre
ased
un
bala
nced
cu
rren
ts &
losses in
mo
tors
, %
NO LOAD CURRENT
FULL LOAD CURRENT
LOSS
CPRI-Training Notes
100*.............
)(2
1
22
5
2
4
2
3
2
2
I
IIIIIcurrentTHD n
100*.............
)(2
1
22
5
2
4
2
3
2
2
V
VVVVVvoltageTHD n
The harmonics are classified according their frequencies.
The THD in industries are vary in the range of 5 % and 35 % whereas the individual voltage and current harmonics are (especially odd harmonics i.e., 3rd, 5th, 7th, etc.,) measured as high as 59 %. As per the IEEE-519-1992, the THD be limited to a maximum value of 5 % with no individual voltage or current harmonic to exceed 3 %, for the voltage level up to 69 kV. In different countries the harmonic limits have been specified . Similar guide lines may be introduced in India also.
The effects of harmonics are :
1. Flickering screens: Triple-N harmonic currents sum in the neutral conductor. The neutral and protective conductor are combined and connected to the structure of the building. As a result, neutral return currents can flow anywhere in the metal structure of the building and create controllable magnetic fields. These fields can result in flicker of computer screens. Neutral current always needs to be returned to the point of common coupling using a separate conductor.
2. Overheating of transformers: Transformers are affected in two ways. Firstly, the eddy current losses which are about 10 % at full load are being increased with the square of the harmonic number. These eddy current losses will double for the transformer which are catering the power supply to power electronic equipment loads. This will increase the operating temperature much higher and a shorter life. Secondly, the triple-N harmonic currents in delta winding will circulate in the winding. The circulating current increase winding loss. The triple-N harmonics are absorbed in the winding of delta connected transformer and do not propagate onto the supply but non-triple-N harmonics pass through.
3. Induction motors: Voltage harmonics cause extra losses in induction motors. The 5th, 11th, 17th,….. harmonics create a counter-rotating field [4], whereas the 7th harmonic creates a rotating field beyond the motor’s synchronous speed. The resulting torque pulsing causes wear and tear on couplings and bearings. Since the speed is fixed, the energy contained in these harmonics is dissipated as extra heat, resulting in premature ageing. Harmonic currents are also induced into the rotor causing further excess heating. The additional heat reduces the rotor/stator air gap, reducing efficiency even further. Variable speed devices cause their own range of problems. They tend to be sensitive to dips, causing disruption of synchronised manufacturing lines. They are often installed some distance from the motor and cause voltage spikes due to the sharp voltage rise times. Special care has to be taken at start-up of motors after a voltage dip when the motor is normally operating at close to full load. The extra heat from the inrush current at start-up may cause the motor to fail.
4. Overheating of conductors due to skin effect: The alternating current tends to flow on the outer surface of a conductor. This is known as skin effect and is more pronounced at high frequencies. Skin effect is normally
CPRI-Training Notes
ignored because it has very little effect at power supply frequencies but above 350 Hz, i.e. the 7th harmonic and above, skin effect will become significant, causing additional loss and heating. Where harmonic currents are present, designers should take skin effect into account and de-rate the cables accordingly. Multiple cable cores or laminated busbars can be used to overcome this problem.
5. Correct functioning of process control equipment: Severe harmonic distortion can create additional zero -
crossings within a cycle of the sine wave, affecting sensitive measurement equipment. Synchronisation of
process control equipment in continuous manufacturing may be disturbed and PLC devices may lock up.
6. Problems with power factor correction equipment: Power factor correction capacitors are generally used to
draw the current with leading power factor to offset lagging current of inductive load. The impedance of PFC
capacitor reduces as the frequency increases, while the source impedance is generally inductive and increases
with frequency. The capacitor is therefore likely to carry a quite high harmonic currents and, unless it has
been specifically designed to handle them, damage can result. A potentially more serious problem is that the
capacitor and the stray inductance of the supply system can resonate at or near one of the harmonic
frequencies (which, of course, occur at 100 Hz intervals). When this happens very large voltages and currents
will be generated, often leading to the catastrophic failure of the capacitor system. Harmonic frequencies may
coincide with resonant frequencies of the combined stray inductance and power factor correction (PFC)
equipment, creating excessive voltage or current and leading to premature failure. Moreover, as a general
problem, measurement devices may not correctly measure the loading of the PFC, as they incorrectly measure
the harmonic content in the current.
7. Overloaded neutrals: In a 3-phase 4 wire system, there are 3-phase conductors and a neutral conductor,
which carries the unbalance between the 3-phases. When there are harmonics in the system and the loads on
all phases are equal, the fundamental currents cancel out, but the harmonic currents do not cancel out,
especially triple-N harmonics add together. The effective third harmonic neutral current will increase. For
example 70 % third harmonic current in each phase increases the neutral current by 210 %. In most of the
installations, 3½ core cables are used. This half sized neutral is getting overloaded due to the presence of
triple-N harmonics and getting burnt. At many places the neutral currents were measured in the range of 150 –
180 %. In order to avoid the failure of neutral conductor, the de-rating of cable can be adopted based on the
IEC 60364-5-523 standard. At 70 % of 3rd
harmonics the cable de-rating factor will be 0.6.
8. Nuisance tripping of protective relays: Residual current circuit breakers (RCCB) operate by summing the
current in the phase and neutral conductors and, if the result is not within the rated limit, disconnecting the
power from the load. Nuisance tripping can occur in the presence of harmonics for two reasons. Firstly, the
RCCB, being an electromechanical device, may not sum the higher frequency components correctly and
therefore trips erroneously. Secondly, the kind of equipment that generates harmonics also generates
switching noise that must be filtered at the equipment power connection. The filters normally used for this
purpose have a capacitor from line and neutral to ground, and so leak a small current to earth. This current is
limited by standards to less than 3.5 mA, and is usually much lower, but when equipment is connected to one
circuit the leakage current can be sufficient to trip the RCCB. Nuisance tripping of miniature circuit breakers
(MCB) is usually caused because the current flowing in the circuit will be higher than that expected from
calculation or simple measurement due to the presence of harmonic currents. Most portable measuring
instruments do not measure true RMS values and can underestimate non-sinusoidal currents by 40 %.
9. The flow of harmonic current in the network system increases the distribution network I2R losses and increase the voltage drop at the farthest end by increasing distribution circuit impedance.
CPRI-Training Notes
The harmonics can be suppressed by the use of filters as discussed below [5] :
i. Incorporation of current waveshaping circuits within the equipment to draw the sinusoidal line currents from the supply will suppress the harmonics.
ii. Installation of filters to clean the distorted current waveforms drawn by the loads.
The filters are of three type:
a. Active filters which can be connected either in series or in shunt mode. This technique is well suited for low and medium power levels. These filters are compact. The load current is flowing from load in to the network is separated in to fundamental (50 Hz) and harmonic components. The filter prevents an undesired flow of harmonic current into the network by injecting the required current portions.
b. Passive filter can also be connected either in series or shunt mode. Shunt filter will serve as a short circuit for load harmonic current where as series filter consists of an impedance connected in series with the utility and acts as an open circuit to load harmonic currents. The passive filters are bulky.
c. Hybrid filters combine the passive filter with active filters. In this scheme, the active portion of the filter is connected in series with a passive impedance which is used to block the utility [6].
3.0 MEASUREMENT OF TRUE RMS COMPONENTS
The Root Mean Square is the magnitude of an alternating current which is equivalent to the direct current that
would produce the same amount of heat in a fixed resistive load. The amount of heat produced in a resistor by an
alternating current is proportional to the square of the current averaged over a full cycle of the waveform. In other
words, the heat produced is proportional to the mean of the square, so the current value is proportional to the root of
the mean of the square or RMS. For a perfect sinewave, the RMS value is 0.707 times the peak value (or the peak
value is 2 or 1.414 times the RMS value. If the magnitude of the waveform is simply averaged (inverting the
negative half cycle), the mean value is 0.636 times the peak or 0.9 times the RMS value.
When measuring a pure sinewave, a simple measurement of the mean value (0.636 x peak) and multiply the result by the form factor i.e., 1.11 (form factor=RMS value / mean value = 1.11) making 0.707 times peak and call it the RMS value. This is the approach taken in all analogue meters (where the averaging is performed by the inertia and damping of the coil movement) and in all older and most current, digital multimeters. This technique is described as ‘mean reading, RMS calibrated’ measurement.
CPRI-Training Notes
Figure 2: Waveform of current drawn by computer
This techniqu
e only
works for pure sine
waves and most
of the
places
pure sine
waves do not exist in the real world of an electrical installation. The waveform in Figure 2 is typical of the current waveform drawn by a personal computer. The true RMS value is still 1 A, but the peak value is much higher, at 2.6 A and the average value is much lower, at 0.55 A.
If this waveform is measured with a mean reading, RMS calibrated meter, it would read 0.61 A, rather than the true value of 1 A, nearly 40 % too low. A true RMS meter works by taking the square of the instantaneous value of the input current, averaging over time and then displaying the square root of this average. Perfectly implemented, this is absolutely accurate whatever the waveform. Implementation is, of course, never perfect and there are two limiting factors to be taken into account: frequency response and crest factor.
For the industrial power systems, it is usually sufficient to measure up to the 50th harmonic, i.e., up to a frequency of about 2500 Hz. The crest factor, the ratio between the peak value and the RMS value, is important; a higher crest factor requires a meter with a greater dynamic range and therefore higher precision in the conversion circuitry. A crest factor capability of at least three is required. It is worth noting that, despite giving different readings when used to measure distorted waveforms, meters of both types would agree if used to measure a perfect sinewave. This is the condition under which they are calibrated, so each meter could be certified as calibrated – but only for use on sinewaves.
True RMS meters features are available in many of the multimeters, power analysers, clamp on meters, but these meters are costly.
4.0 CASE STUDIES
4.1 Single phase loads
CPRI-Training Notes
The generally used single equipment that are producing the harmonic distortion are:
1. Switched mode power supply units (SMPS) 2. Electronic ballasts 3. Small UPS or inverters
4.1.1 Switched Mode Power Supply Units
Most of the modern power electronic equipments use SMPS. The SMPS draws pulses of current which contain large amounts of third & higher harmonics and significant high frequency components. A simple filter is fitted at the supply input to bypass the high frequency components from line and neutral to ground but it has no effect on the harmonic currents that flow back to the supply.
The personal computers (PC) are fitted with SMPS and generate current harmonics. Figure 3 gives the measured current harmonics for PCs. The odd current harmonics are on higher side. The current 3rd harmonics are measured in the range of 63.9 - 89.5 %, followed by 5th harmonics 63.4 - 65.7 %, 7th harmonics 39.5 – 43.5 %, 9th harmonics 19.3 - 21.7 % and so on. Because of this increased 3rd harmonics cause overheating of neutral conductors of the feeders connecting to the computers. At many installations, the neutral conductors are being burnt because the cables used are of 3½ core cables. In order to overcome this problem the neutral conductor must be of higher size.
4.1.2 Electronic ballasts
The increased awareness of conservation of energy in lighting sector, the electronic ballasts are being used for
fluorescent lamps. A fluorescent lamp operates much more effectively at a frequency above 10 kHz as compared to
its operation at 50 Hz. Moreover, an electronic ballast has fewer Watt losses and needs no capacitor for power
factor correction. As the losses in electronic ballast are less, it reduces the temperature of the air circulating around
the lamp which decreases the ambient temperature of the lamp and thereby increases the efficiency of both the lamp
and luminaire. These ballasts generate higher frequency voltage in the range of 20 – 25 kHz to ballast the
fluorescent lamp. This will cause the harmonics in the system. The conventional coil wound ballasts consume about
12 – 14 W per 40 W lamp whereas electronic ballast will consume only 0.5 – 1 W per 40 W lamp. But these ballasts
generate harmonics in the system. Figure 4 gives the measured harmonics of typical electronic ballasts without and
with harmonic filters for fluorescent lamps and compact fluorescent lamps (CFL). It can be seen from the Figure 4
that the 3rd
current harmonics of CFL are measured as high as 75.6 %, 5th harmonics 46.5 %, 7
th harmonics 39.5 %,
9th 37.6 % and so on. The current harmonics of electronic ballasts without harmonic filters (low cost) are measured
in the range of 34.2 – 56.5 %, followed by 5th harmonics 22.7 – 34.5 %, 7
th harmonics 15.9 – 24.5 %, 9
th harmonics
13.2 – 18.7 % and so on. Some manufacturers are manufacturing the electronic ballasts with harmonic filter which
are reducing the harmonic distortions but the cost of these ballasts increase by about 60 – 70 %.
CPRI-Training Notes
4.2 Three phase
loads
In 3-phase loads
like Variab
le speed
drives, UPS
units and DC
converter
s in general are usuall
y base
d on the 3-
phase
bridge,
also known as
the six-
pulse bridge because there are six pulses per cycle (one per half cycle per phase) on the DC output. The six pulse bridge produces harmonics at 6n ±1, i.e. at one more and one less than each multiple of six. The magnitude of the harmonics is significantly reduced by the use of a twelve-pulse bridge. This is two six-pulse bridges, fed from a star and a delta transformer winding, providing a 30 degrees phase shift between them. The 6n harmonics are theoretically removed, but in practice, the amount of reduction depends on the matching of the converters and is typically by a factor between 20 and 50. The 12n harmonics remain unchanged. Not only is the total harmonic current reduced, but also those that remain are of a higher order making the design of the filter much easier. Often the equipment manufacturer will have to take some steps to reduce the magnitudes of the harmonic currents, perhaps by the addition of a filter or series inductors. A further increase in the number of pulses to 24,
0
10
20
30
40
50
60
70
80
90
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Cu
rre
nt
harm
on
ics
, %
Harmonic number
Figure 3: Measurement of current harmonics at Computer (PC).
PC 1
PC 2
PC 3
PC 4
0
10
20
30
40
50
60
70
80
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Cu
rre
nt
harm
on
ics
, %
Harmonic number
Figure 4: Measurement of current harmonics at CFL, Electronic ballasts with and without filter.
CFL
Ballast 1
Ballast 2
Ballast 3 (with filter)
CPRI-Training Notes
achieved by using two parallel twelve-pulse units with a phase shift of 15 degrees, reduces the total harmonic current to about 4.5 %. The extra sophistication increases cost, of course, so this type of controller would be used only when absolutely necessary to comply with the electricity suppliers’ limits.
4.2.1 Variable speed drives
In many industries, the fluid flow elements (i.e., pumps and fans) are driven by induction motors because of their robustness, easy maintenance, less cost, etc. The speed of these induction motors will be constant. To control the fluid flow, various control devices like guide vane control, dampers, throttle valve and hydraulic couplings are being used. The efficiency of these control devices at partial flow will be very poor. In order to improve the efficiency of control at partial load and to reduce the power consumption at partial flow, the variable frequency drives are being used to control the speed of the induction motors. These controls are more efficient at partial flow. These controllers convert the 50 Hz AC power to DC and invert back to AC with variable frequency to regulate the speed of the motors. While converting and inverting the power supply, these equipment generate the harmonics in the system. The use of variable frequency drives reduce the energy consumption by 15 – 25 % for the varying flow applications. Figure 5 shows the measured current harmonics of variable frequency drives. It can be seen from the Figure 5 that the 3rd current harmonics are varying between 6.5 – 8.5 %, followed by 5th harmonics 35.6 – 76.5 %, 7th harmonics 31.4 – 63.4 %, 9th harmonics 5.4 – 11.4 %, 11th harmonics 17.8 – 35.4 %, 13th harmonics 14.5 – 24.2 % and so on.
4.2.2 Un-interrupted Power Supply (UPS) units
To cater the need of un-interrupted power supply to the equipment, UPS systems are being used. Most of the places, the grid interactive UPS are being used. Whenever the grid power supply will be there, UPS will take the grid supply as incoming and supply the power to the load by converting and inverting. Whenever the grid supply is not there, it will draw the DC power from battery bank and supply the power to load by inverting. Most of the places, the UPS power supply is being used for power electronic equipment like PCs, controllers, etc. These loads generate lot of harmonics. The good design UPS has to filter the harmonics. In many cases, it was observed that instead of filtering the harmonics the UPS generate the harmonics. Figure 6 gives the measured voltage harmonics at UPS input and output. The UPS has filtered the 5th voltage harmonics from 0.6 % to 0.4 %, 7th voltage harmonics from 2.7 % to 0.2 %. Figure 7 gives the measured current harmonics at UPS input and output. The 3rd current harmonics are reduced from 32.8 % to 6.4 %, 5th current harmonics are reduced from 25 % to 22.4 %, 7th harmonics are increased from 11.1 % to 18.4 %, 9th harmonics are reduced from 4.8 % to 0.6 %, 11th harmonics are increased from 0.8 % to 5.2 %, 13th harmonics are increased from 1 % to 6.3 % and 17th harmonics are increased from 0.2 – 5.7 %.
CPRI-Training Notes
5.0 CONCLUSIO
NS
The use of
more and
more power electr
onic equipment
in the distribution
network, the power quality
is being pollut
ed. The
polluted
power supply influe
nce more
losses in the
system,
reduction in the quality of the products and reliability of power supply.
The use of power conditioners will suppress the harmonics, control the voltage unbalance, improve the power factor, etc.. The incorporation of power conditioners in the system proves to be economically viable.
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
2 3 4 5 6 7 8 9 10 11 12 13
Vo
ltag
e h
arm
on
ics
, %
Harmonic number
Figure 6: Harmonic voltage measurement at UPS input and output
Input THD = 3.0 %
Output THD = 0.7 %
Figure 5: Measurement of current harmonics at variable
frequency vdrives.
0
10
20
30
40
50
60
70
80
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Harmonic number
Cu
rren
t h
arm
on
ics,
%
VFD 1
VFD 2
VFD 3
VFD 4
CPRI-Training Notes
REFERENCES
1. R . K. Aggar
wal, M.
Weinhold and
R. Zurowski, “Pow
er qualit
y impr
ovement in distribution systems”, Proc. of International Conference on power generation, system planning and operation, at IIT, New Delhi, 12 -13, Dec., 1997, pp. 28 - 38.
2. Vijay B. Bhavaraju and Prasad N. Enjeti, “An active line conditioner to balance voltages in a three phase system,” IEEE Transactions on Industry applications, Vol.32, No. 2, March/April, 1996, pp. 287 - 292.
3. Rajanbabu, P. C. 1999. Harmonics, Proc. Training Programme on Conducting Energy Audit, Central Power
Research Institute, Energy Research Centre, Trivandrum-695017, 105-110.
4. Ramakrishnaiah R. , “ Impact of harmonics and voltage fluctuation in reactive power problems”, Electrical India, 15th Oct. 1996, pp. 25 - 27.
5. Ned mohan and Girish R Kamath , “Active power filters-Recent advance”, Sadhana, Vol.22, Part 6, Dec. 1997, pp. 723 - 732.
6. Abraham, P. 1990. Strategies for improving the quality of power supply, Proc. Conf. on Role of Innovative Technologies and Approaches for India’s power sector, PACER-TERI, 7 Jorbagh, New Delhi-110003, I ,1-9.
Figure 7: Harmonic current measurement at UPS input and
output
0
5
10
15
20
25
30
35
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Harmonic number
Cu
rren
t h
arm
on
ics,
%
Input THD = 28.8 %
Output THD = 46.5 %
CPRI-Training Notes
FIRE FIGHTING
ELECTRICAL FIRES
Any fire started by electrical equipment must be a class A, B, C or D fire. Normal procedure is to cut off
the supply of electricity and use an extinguishing method appropriate to burning material.
Special agents which are non-conductors of electricity and non-damaging to equipment should be used in
case of any doubt about positive isolation of electric supply.
FIRE- ITS ANATOMY & CLASSIFICATION
Nature of Fire
Fire is as old as human civilisation. Fire of controlled nature has been part and parcel of day to day life.
As the proverb goes ―FIRE IS A GOOD SERVANT BUT BAD MASTER‖, fire plays only constructive
role in generating electricity.
What is Fire?
Fire is an exothermic chemical reaction resulting from combination fuel, heat and oxygen.
CLASSIFICATION OF FIRES and EXTINGUISHING MEDIA FOR PARTICULAR CLASS
Classification of Fires
Fires are classified on the basis of type of fuel involved. Method of extinguishment & type of
extinguishing media depends upon the class of fire.
As per Indian Standards : IS : 2190 - 1979, fires are classified as follows :
Class
of
Fire
Type of fuel / material
involved
Method of
extinguishment
Extinguishing
Media to be used
A Ordinary Solid
Combustibles
e.g. Wood, Paper, Grass,
Plastics
Cooling fuel below
its ignition point.
Water
B Flammable Liquids,
Liquefiable solids
e.g. Fuel Oil, LSHS,
Diesel, Gasoline (Petrol),
Paints, Petrochemicals.
Blanketing fuel
surface in the bulk
fire.
Protein Foam AFFF,
Alcohol Resistant Foam
Flame Suppression
in the spillage fire.
CO2, D.C.P., Halon
C Flammable Gases
e.g. Acetylene,
Hydrogen,LPG,
Associated Gas, Natural
Gas
Starvation by the
control of fuel
supply.
No medium is required
Inhibition of the
burning fuel at fast
rate with an inert gas.
CO2, D.C.P., Halon
CPRI-Training Notes
D Combustible Metals
e.g. Magnesium,
Aluminium, Zinc, Sodium,
Potassium, etc.
Inhibition of the
chain reactions of
combustion process
Special D.C.P.
II. Smothering:
In very simple word it can be understand as cutting of O2 (air) supply.
This method can be accomplished by covering a burning surface with blanket, sand, DCP, foam,
etc.
III. Cooling:
If heat generated during combustion can be dissipated at footer rate than generation by some
means, the combustion can not sustained by proper cooling, the heat lost will be more than the
production and fire will die down.
IV. Chain Inhibition:
Fire Triangle
Fuel O2
Oxygen Heat
Heat
Fuel
Basic need of fire is these three elements in proper proportion without which fire can not
involve.With removing any of the side of fire triangle, we can extinguish fire. Depending upon
these three parts of fire triangle, there are three extinguishing methods.
V. Chemical chain inhibition combustion consists of repaid chain reactions involving hydrogen atom
and other active species and free oxygen atom. By applying proper chemicals, these chain reactions
can be arrested e.g. D.C.P.
FIRE PREVENTION
Fire safety has four legs as shown below :
1. Fire Protection : Elimination of contribution
2. Fire Prevention : Elimination of causes
3. Quality control
4. Preventive maintenance
The best way of fire safety is to eliminate the cause of fire i.e. fire prevention.
I) Good Housekeeping
II) No smoking (or separate preparation of smoking zone)
III) Use of fire resistant paint
IV) Electrical safety
V) Fire check doors
CPRI-Training Notes
VI) Compartmentalisation
VII) Separate storage of Hazardous chemicals
VIII) Naked Flame safety
IX) Use of earth leakage and current balance relays and thermostat, fireproof chokes.
Do‘s and Don‘ts for Prevention of Electrical Fire
1) Ensure that current ratings of wires, cables and accessories are equal to or higher than
maximum possible loads.
2) Ensure that all electrical wires and cables are protected by fuses.
3) Use of MCBs or cartridge fuses instead of wire fuses.
4) Ensure switch boards, terminal boards, joints etc. are not fixed close to combustible
material.
Use only those electrical equipment, cables/wires and accessories which comply with relevant I.S.
NOTE:
All portable fire extinguishers should be wall mounted (1000 mm above ground/floor level).
Types of fires are:
Class A: Wood,paper,cloth, trash,plastics—solidsthatarenot metals.
ClassB:Flammableliquids—gasoline,oil,grease,acetone.Includesflammable gases.
Class C: Electrical—energizedelectricalequipment. As long asit‘s―pluggedin.‖
Class D:Metals—potassium,sodium,aluminum, magnesium. RequiresMetal-X,foam, andother
specialextinguishingagents.
Differenttypesof fire extinguishersare designedto fight differentclassesof fire.
The three most common types of fire extinguishersare:
1. Water(APW)
2. CarbonDioxide(CO2)
3. DryChemical(ABC,BC,DC)
Howto Use aFire Extinguisher: It‘seasytorememberhowtousea fire
extinguisherifyouremembertheacronym PASS:
Pull
Aim
Squeeze
CLEANING OF PARTS
With flammable solvents
(1) Adequate ventilation must be available to avoid fire, explosion and health hazards.
(2) Avoid breathing solvent vapours.
(3) Keep open flames and sparks away from flammable liquids and their vapours.
(4) Metal nozzle of a hose for spraying flammable solvents shall be grounded.
CPRI-Training Notes
With compressed air
(5) Goggles shall be used when blowing out dust with compressed air.
PREVENTING FIRES AND EXPLOSIONS
(1) Waste paper, rags and other combustible material should not be allowed to accumulate.
(2) Flammable liquids shall be kept in approved safety cans and identified by proper labels.
(3) Varnish, paints, lacquers and thinners are highly flammable and should be stored away from all-
open flames or possible sources of ignition. Matches and open flames should not be used where
varnish, paint or lacquer is being applied with a spray gun.
(4) Open flames and smoking are prohibited in all areas where flammable liquids or gases are stored
or being used. Such areas shall be posted with appropriate warning signs.
(5) All employees should be familiar with the location and proper use of fire extinguishers in their
work area.
(6) No employee should smoke or use matches or open flames on customer‘s premises
FIRE SAFETY & EXTINGUISHER USE
OBJECTIVE
1. Understand the combustion process and different fire classes.
2. Understand fire extinguisher types, operating procedures.
3. Understand basic fire fighting concept.
THE COMBUSTION PROCESS
CPRI-Training Notes
1. Three components
2. Need all three components to start a fire
3. Fire extinguishers remove one or more of the components
FIRE CLASSES
A – Wood, Paper, Cloth, etc.
B - Liquids, Grease
C – Electrical Equipments
D – Combustible Metals
FIREEXTINGUISHER TYPES
Class “A” Fires only
2.5 gal, water (up to 1 minute discharge time)
Has pressure gauge to allow visual capacity check.
30-40 ft maximum effective range
Can be started and stopped as necessary
Extinguishes by Cooling Burning material below the ignition point.
Class “B” –Carbon Dioxide (Co2)
2.5 -100 lb of CO2 (8-30 seconds discharge time)
Has no pressure gauge, capacity verified by weight
3-8 ft maximum effective range
Extinguishes by smothering burning materials.
Effectiveness decreases as temperature of burning material increases
Class ―A‖ ―B‖ OR ―C‖ fires
1. 2.5-20 lb. dry chemical (ammoniumphosphate)
2. 8-25 seconds discharge time
3. Has pressure gauge to allow visual capacity check
4. 5-20 ft maximum effective range
5. Extinguishes by smothering burning materials
RESSURIZED
WATER COOLING CLASS ―A‖
CPRI-Training Notes
CARBON DIOXIDE SMOTHERING CLASS ―B‖ & ―C‖
MULTIPURPOSE
DRY CHEMICAL SMOTHERING CLASS ―A‖ ―B‖& ―C
SUMMARY
1. Combustion process ( Fire Triangle)
2. Class A, B, C, D, Fires
3. Types of portable fire extinguishers
4. A, B, & C,
5. Operating procedures
6. Capacity and limitations
7. Basic firefighting concepts R.A.C.E. P.A.S.S.
CPRI-Training Notes
Legal Issues of Contracts & CVC guidelines
Dr. H. N.Nagamani, CVO/ Joint Director, CPRI, Bangalore
1.0 Introduction
Corruption has become the bane of our society. It has assumed alarming proportions and encompasses all spheres of
life. There was a time when socially, a corrupt person was not considered a desirable person. But today we have
reached such a cynical stage that corruption is not only taken for granted but people with money, however ill gotten
it may be are respected by the society. The spreading cult of consumerism and a desire for an ostentatious life style
tempts many to make money by hook or crook. This not only results in vicious cycle of corruption but also
increased criminalization of the society. The recent exposes, disclosures and a spate of financial scams have very
dramatically highlighted the extent of corruption in high places, in public life.
Corruption can be tackled only by sustained and coordinated effort. In the context of Government organizations and
PSUs it is imperative and there is transparency and accountability in governance. The root cause of poor governance
lies in corruption. The poor governance in turn, affects the productivity, efficiency, image and the profitability of
the organization. One area which not only affects the bottom line of the organization considerably but is also
corruption prone is the area of contract management. Any mismanagement in the award and execution of contracts
may result in heavy leakages of revenue and adversely affect the image and profitability of the organization.
Keeping this perspective in view, the Chief Technical Examiner‘s (CTE) Organization of Chief Vigilance
Commission (CVC) has published a booklet titled as ―Common irregularities / Lapses observed in Stores / Purchase
contracts and Guidelines for improvement in procurement system‖. The booklet highlights the lapses/irregularities
in the award and execution of electrical, mechanical and other allied contracts is being issued. The lapses have been
explained and discussed with illustrations as far as possible. The aim of the booklet is not to indulge in fault finding
exercise but to help improve the systems and procedures in the organizations so that the project/contract
management is more objective, transparent and professional.
The course material covers the salient features of CVC guidelines for procurement.
2.0 Purchase Manual
The cardinal principle of any public buying is to procure the materials / services of the ‗specified‘ quality, at the
most competitive prices and in a fair, just, transparent manner and shall promote competition. To achieve this end, it
is essential to have uniform and well documented policy guidelines in the organization so that this vital activity is
executed in a well-coordinated manner with least time and cost overruns. A codified purchase manual containing
the detailed purchase procedures, guidelines and also proper delegation of powers, wherever required needs to be
made by all the organizations so that there is systematic and uniform approach in the decision-making. Such an
integrated approach is likely to put a cap on the corruption and would also ensure smoother and faster decision-
making.
3.0 Filing System
The procurement files are very important and sensitive documents and thus there is a need to have a single file
system with proper page numbering. In case of urgency, if opening of the part files is unavoidable, the same should
CPRI-Training Notes
thereafter be merged with the main file. The decisions and deliberations of the individuals or the Tender
Committees also need to be properly recorded and well documented.
4.0 Provisioning
It has been noticed that in certain cases excessive, fraudulent andinfructuous purchases were made without taking
into consideration theimportant aspects like available stocks, outstanding dues / supplies, pastconsumption pattern
and average life of the equipment / items etc.
The provisioning of the stores needs to be done with utmost care takinginto account the available stock, outstanding
dues / supplies, the pastconsumption pattern, average life of the equipment / spares. The requirementsalso need to
be properly clubbed so as to get the most competitive and bestprices. The requirements should not be intentionally
bifurcated / split so as toavoid approval from higher authorities.
5.0 Estimated Rates
As the estimated rate is a vital element in establishing the reasonableness of prices, it is important that the same is
worked out in a realistic and objective manner on the basis of prevailing market rates, last purchase prices,
economic indices for the raw material/labour, other input costs, IEEMA formula, wherever applicable and
assessment based on intrinsic value etc.
6.0 Notice Inviting Tender
Against the most preferred and transparent mode of Global tender enquiry/Advertised tender enquiry, some of the
Organizations are generally issuing limited tender inquiry to select venders, irrespective of the value of purchase. In
order to give wide publicity, generate enough competition and to avoid favoritism, as far as possible, issue of
Advertised/Global tender inquiries should be resorted to and published in ITJ and select National Newspapers. The
copies of the tender notices should be sent to all the registered/past/likely suppliers by UPC and also to the Indian
Missions /Embassies of major trading countries in case of imported stores.
7.0 Tender / Bid Document
The terms and conditions being stipulated in the bid documents by some of the Organizations are quite insufficient
and sketchy. Sometimes, the bid document contain obsolete, unwanted matter and conflicting and vague provisions,
resulting in wrong interpretation, disputes and time & cost overruns. The important clauses relating to Earnest
money, Delivery Schedule, Payment terms, Performance/Warrantee Bank Guarantee, Pre-despatch inspection,
Arbitration, Liquidated Damages/Penalty for the delayed supplies and Risk-purchase etc. are not being incorporated
in the bid documents. All these clauses are important for safeguarding the interest of the purchaser and also have
indirect financial implications in the evaluation of offers and execution of the contracts.
A proper arrangement for receipt of tenders at scheduled date and time through tender box needs to be adopted.
In order to give equal opportunity to all the bidders and to maintain sanctity of tendering system, it is of paramount
importance that any change in the tender terms & conditions, specifications and tender opening date etc. be notified
to all the bidders, sufficiently in advance of the revisedtender opening date.
Tenders shall be opened in public in the presence of bidders.
CPRI-Training Notes
8.0 Post Tender Negotiations
As post tender negotiations could often be a source of corruption, it is directed that there should be no post-tender
negotiations except with L-1, in certain exceptional situations. Such exceptional situations would include
procurement of proprietary items, items with limited sources of supply and items where there is suspicion of a cartel
formation. The justification and details of such negotiations should be duly recorded and documented without any
loss of time.
9.0 Technical Evaluation of Tenders
Once it has been established that the offers meet the laid down specifications, the question of ‗grading‘ as well as
any ‗pick and choose‘ should not arise. The contract needs to be awarded to the lowest bidder meeting the laid down
specifications.
10.0Purchase Preference to Public Sector Enterprises
The instructions / guidelines circulated by Department of Public Enterprises for granting purchase preference to the
Central Govt., Public Sector Enterprises / Joint Ventures need to be scrupulously followed as also brought out by
CVC in the instructions circulated vide letter No. 98 / Ord. / 1 dtd. 15.03.99.
11.0Consideration of Indian Agents
It is essential to verify the genuineness of the prices quoted by the Indian Agent, the nature of services which would
be available from Indian Agent and compliance of Tax Laws by the Indian Agent and, to prevent leakage of foreign
exchange. In view of this, the following aspects shall be examined:-
a. Foreign Principal‘s proforma invoice indicating the Commission payable to the Indian Agent,
nature of after sales service to be rendered by the Indian Agent.
b. Copy of the agency agreement with the foreign principal and the precise relationship between
them and their mutual interest in the business.
c. The enlistment of the Indian Agent with Director General of Supplies & Disposals under the
Compulsory Registration Scheme of Ministry of Finance.
12.0Reasonableness of Prices
It is very important to establish the reasonableness of prices on the basis of estimated rates, prevailing market rates,
last purchase prices, economic indices of the raw material / labour, other input costs and intrinsic value etc., before
award of the contract.
13.0Advance Payment & Bank Guarantee
The advance payments need to be generally discouraged except in specific cases. Wherever payment of advance is
considered unavoidable, the sameshould be interest bearing as per CVC guidelines and be allowed after getting an
acceptable Bank Guarantee for an equivalent amount with sufficient validity so as to fully protect the Govt. interest.
Some reasonable time should be stipulated for submission of Bank Guarantee so that contractual remedies could be
enforced, if required.
CPRI-Training Notes
14.0Performance Bank Guarantee
In order to safeguard the Govt. interest, it would be appropriate to take reasonable amount of Performance Bank
Guarantee valid upto warranty period for due performance of the contract. The validity of the Bank Guarantees
needs to be carefully monitored and whenever extension in the delivery period is granted, the validity of Bank
Guarantee should also be appropriately extended so as to protect the Govt. interest. The genuineness of the BGs
should be checked from the issuing bank.
15.0Stipulation of delivery period in the contract
Delivery period is the essence of any contract. The specific delivery period for supply as per the terms of delivery
such as station of dispatch / destination and completion of installation with the necessary provision for Liquidated
damages / Penalty clause in the event of delay in supplies/ installation needs to be incorporated in the contract.
16.0Guarantee / Warranty Terms
Detailed guarantee/warranty clause embodying all the safeguards be incorporated in the tender enquiry and the
resultant contract. It also needs to be ensured that in installation/commissioning contracts, the guarantee/ warranty
should reckon only from the date of installation/commissioning.
17.0Post-contract Management
After conclusion of the contract, any relaxation in the contract terms / specifications should be severely
discouraged. However, in exceptional cases where the modifications/amendments are considered to be absolutely
essential, the same should be allowed after taking into account the financial implications for the same.
It is essential to accord priority to the post contract follow up. The delivery period should be extended on bonafide
request and not in a routine and casual manner. After expiry of delivery period, the consignees should be refrained
from exchanging correspondence with the supplier. In case of delay in supplies by the supplier, the liquidated
damages to the extent possible need to be recovered. Also in case of delay attributable on the part of the supplier,
the L/C extension charges should be to supplier‘s account. In nutshell, there is a need to discipline the suppliers so
that the non-performers could be weeded out and the suppliers which can be relied upon with consistent
performance, in terms of quality and delivery schedule are encouraged.
Reference
1. Common irregularities / lapses observed in stores / purchase contracts and guidelines for improvement in the
procurement system – by Chief Technical Examiner Organization of Central Vigilance Commission, Government
of India. Year 2002.
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