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Preface
This report presents the summarizing of experiences and knowledge I have gathered during the
my implant training which consisted of 12 weeks starting from 4th January 2016 to 24th March
2016 at Ceylon Electricity Board. The Report is made up of three chapters including
Introduction, Training Experience, and Conclusion.
Information about the training establishments, main functions, structures of the regarding
organizations, present performance, strengths, weaknesses, usefulness to Sri Lankan society
are discussed in Chapter one. Suggestions to improve the performance of the organizations are
also included in this chapter.
The experience and knowledge I have gained within the period are presented in the second
chapter comprising duties and equipment of particular training establishments.
Last chapter is an evaluation of the current Industrial Training program of the University of
Ruhuna and my opinions about the implant training.
I tried my best to include all important information and experience I gathered during my
training period.
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Acknowledgement
Initially, I would like to give my sincere thanks to all the persons who contributed in various
ways to give me this valuable opportunity of gaining practical knowledge of engineering field
during the training period.
I would like to thank Dr. Keerthi Gunawikrama, Who the Head of the Department of Electrical
and Information Engineering and all other academic staff members of the Department of
Electrical and Information Engineering for giving me this great opportunity of gaining
practical knowledge of Electrical Engineering field. I would like to thank the National
Apprentice and Industrial Training Authority (NAITA) officials for coordination of training.
Then, I would like to thank Deputy General Manager (Training) Ceylon Electricity Board, Mrs.
K.A.C.K Premarathne Electrical Engineer (Internal Training) CEB Training Centre & other
executive staff members of CEB Training Centre, Ceylon Electricity Board for giving me all
the facilities in order to make my training a success.
Sathruwan P.C
Department of Electrical and Information Engineering
Faculty of Engineering
University of Ruhuna
iii
Table of Contents Preface ......................................................................................................................................... i
Acknowledgement ..................................................................................................................... ii
1 Introduction to the Training Establishment ....................................................................... 1
1.1 History of Ceylon Electricity Board ............................................................................ 1
1.2 Vision .......................................................................................................................... 1
1.3 Mission ........................................................................................................................ 1
1.4 Objectives .................................................................................................................... 2
1.5 Organizational Structure of CEB ................................................................................ 3
1.6 Electricity Generation ................................................................................................. 3
1.7 Transmission ............................................................................................................... 5
1.8 Distribution.................................................................................................................. 5
2 Technical Details ............................................................................................................... 6
2.1 Transmission (Operation & Maintenance) Galle Region ............................................ 7
2.1.1 Components of a Grid Substation ........................................................................ 7
2.1.2 Protection schemes in CEB system.................................................................... 13
2.1.3 Distribution Feeder Protection ........................................................................... 13
2.1.4 Transformer Protection ...................................................................................... 14
2.1.5 Transmission line protection .............................................................................. 15
2.2 System Control Centre .............................................................................................. 16
2.2.1 System Stability Limits ...................................................................................... 16
2.2.2 System Operation ............................................................................................... 17
2.2.3 Operational Priorities ......................................................................................... 17
2.2.4 Water Usage Priorities ....................................................................................... 17
2.2.5 Under-Frequency Load Shedding ...................................................................... 18
2.2.6 Economic Dispatch and Unit Commitment ....................................................... 18
2.3 Transmission and Generation Planning ..................................................................... 19
2.3.1 Generation Planning ........................................................................................... 19
iv
2.3.2 Preparation of Demand Forecast methodology .................................................. 20
2.3.3 Generation Expansion Planning Methodology .................................................. 22
2.3.4 Transmission Planning ....................................................................................... 23
2.4 Projects & Heavy Maintenance – DD4 ..................................................................... 25
2.4.1 Tower Line Maintenance ................................................................................... 27
2.4.2 Hot line maintenance ......................................................................................... 28
2.4.3 Cold line maintenance ........................................................................................ 28
2.4.4 Primary Substations (PSS) ................................................................................. 28
2.5 Distribution Division –Southern Province ................................................................ 29
2.5.1 Line Support....................................................................................................... 29
2.5.2 Maintenance Tools and Accessories .................................................................. 30
2.5.3 Transformer maintenance .................................................................................. 32
2.6 Laxapana Hydro Power Complex ............................................................................. 36
2.6.1 Introduction ........................................................................................................ 36
2.6.2 Main components of a typical hydro power plant ............................................. 37
2.6.3 Electrical System of Laxapana Power Station ................................................... 39
2.7 Lakvijaya Power Station ........................................................................................... 46
2.7.1 Coal feeding process .......................................................................................... 46
2.7.2 Coal burning process.......................................................................................... 47
2.7.3 Primary air and secondary air supply in burning process .................................. 47
2.7.4 Air pre heater ..................................................................................................... 47
2.7.5 Boiler of the Lakvijaya power station ................................................................ 47
2.7.6 Bottom ash handling .......................................................................................... 48
2.7.7 Fly ash handling ................................................................................................. 48
2.7.8 SOX and NOX reduction in flue gas ................................................................. 48
2.7.9 Electrical details of the plant .............................................................................. 49
2.7.10 Auxiliary systems............................................................................................... 50
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3 Management Experience .................................................................................................. 51
3.1 Management details ................................................................................................... 51
3.2 Labor Management ................................................................................................... 51
3.3 Safety Management ................................................................................................... 52
4 Summary and Conclusions .............................................................................................. 55
4.1 Summary ................................................................................................................... 55
4.2 Conclusion ................................................................................................................. 56
Abbreviation ............................................................................................................................ 57
References ................................................................................................................................ 59
vi
List of figures
Figure 1:1 Ceylon Electricity Board Logo ................................................................................. 1
Figure 1:2 the Divisions of CEB for Distribution ...................................................................... 2
Figure 1:3 Organizational Structure of CEB ............................................................................. 3
Figure 2:1 Surge arrestor ........................................................................................................... 8
Figure 2:2 Arrangement of a CVT ............................................................................................. 8
Figure 2:3 Current transformer .................................................................................................. 9
Figure 2:4 SF6 circuit breaker ................................................................................................. 10
Figure 2:5 Classification of Circuit Breakers .......................................................................... 10
Figure 2:6 Isolator .................................................................................................................... 11
Figure 2:7 Power transformer of Matara GSS ......................................................................... 12
Figure 2:8 Normal Feeder ........................................................................................................ 13
Figure 2:9 Transformer bay ..................................................................................................... 14
Figure 2:10 132 kV Line feeder ............................................................................................... 15
Figure 2:11 System Control center .......................................................................................... 16
Figure 2:12 schematic representation of the transmission planning process ........................... 24
Figure 2:13 Sections of the transmission tower ....................................................................... 25
Figure 2:14 Identification of tower types................................................................................. 26
Figure 2:15 CEB workers on a cold line maintenance ............................................................ 28
Figure 2:16 D-Complete .......................................................................................................... 30
Figure 2:17 H-Connector ......................................................................................................... 30
Figure 2:18 Angle Binding ...................................................................................................... 30
Figure 2:19 End Binding .......................................................................................................... 31
Figure 2:20 Line Binding ......................................................................................................... 31
Figure 2:21 160KVA transformer ............................................................................................ 32
Figure 2:22 Single pole transformer arrangement ................................................................... 33
Figure 2:23 Double pole transformer arrangement .................................................................. 33
Figure 2:24 Cubical transformer arrangement ......................................................................... 34
Figure 2:25 Welded Neutral Earth and Copper Rod ................................................................ 34
Figure 2:26 Earth Tester (Megger) .......................................................................................... 35
Figure 2:27 Insulation oil tester ............................................................................................... 35
Figure 2:28 Laxapana Complex ............................................................................................... 36
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Figure 2:29 Main components of a typical hydro power plant ................................................ 37
Figure 2:30 Static Excitation System ....................................................................................... 40
Figure 2:31 Brushless Excitation System ................................................................................ 40
Figure 2:32 Single phase transformer use in Laxapana Old .................................................... 42
Figure 2:33 Transformer of Old Laxapana power station ....................................................... 43
Figure 2:34 Old Laxapana switchyard arrangement ................................................................ 44
Figure 2:35 New Laxapana switchyard arrangement .............................................................. 45
Figure 2:36 Normal Start & Control Sequence of a Hydro Turbine ........................................ 45
Figure 2:37 Coal yard and the jetty of the Lakvijaya power plant .......................................... 46
Figure 2:38 Coal feeding process in the Lakvijaya power plant ............................................. 46
Figure 2:39 Flow diagram of coal burning .............................................................................. 47
Figure 2:40 Submerged conveyor belt system which is used to remove bottom ash .............. 48
Figure 2:41 Generator and HP, LP and IP of the Lakvijaya power plant ................................ 49
List of tables
Table 1-1 Details of Existing Hydro Plants ............................................................................... 4
Table 1-2 Details of Existing Thermal Plants ............................................................................ 5
Table 2-1 Training Schedule of CEB......................................................................................... 6
Table 2-2 Different transformer cooling methods ................................................................... 11
Table 2-3 System stability limits ............................................................................................. 16
Table 2-4 under frequency load shedding ................................................................................ 18
Table 2-5 Variables used for Econometric modelling ............................................................. 20
Table 2-6 Demand forecast of 2014 ......................................................................................... 21
Table 2-7 Main tower types ..................................................................................................... 26
Table 2-8 Laxapana Complex details ...................................................................................... 36
Table 2-9 Auxiliary Transformer specifications of O/L and N/L power stations .................... 41
Table 2-10 Unit Transformer specifications of O/L and N/L power stations .......................... 43
Table 3-1 Effects of Electric Current on the Human Body ..................................................... 52
1
Chapter One
1 Introduction to the Training Establishment
1.1 History of Ceylon Electricity Board
Ceylon Electricity Board (CEB) was established on the 1st of November 1969 under the Act of
Parliament No.17 of 1969, which had been subsequently amended by Act No 31 of 1969 and
Act No 29 of 1979. CEB was established under the Ministry of Irrigation and Power. However
at present it is under Ministry of Power and Energy. CEB is the major electric power and
electricity service provider of Sri Lanka which is responsible for generation, transmission, and
most of the distribution of electrical power in Sri Lanka.
Figure 1:1 Ceylon Electricity Board Logo
1.2 Vision
“Enrich life through power”
1.3 Mission
“To develop and maintain efficiency, coordinated and economical system of electricity Supply
to the whole of Sri Lanka, while adhering to our core values”. Those core values are:
Quality
Service to the nation
Efficiency and effectiveness
Commitment
Safety
Professionalism
Sustainability
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1.4 Objectives
To generate or buy adequate amount of electrical energy in most effective and efficient
manner and supply power to satisfy all requirements of the country.
To construct new power stations substations and maintain and operate existing
power stations and substations.
To give a better service in the areas that distribution system is control by the Ceylon
Electricity Board.
To develop a sound, adequate and uniform electricity policy and for that purpose to
control and utilize national power resources.
The CEB‟s mission would reveal that the functions of the CEB encompass major human, social
and economic aspects. The availability, reliability and quality dimensions are their functions
to delight the customer. CEB has divided Sri Lanka into four divisions due to the easiness
of management. There are some private companies which are joining with them in
generation and distribution process. Generation part is done only by CEB (major provider) and
LECO (Lanka Electricity Company (pvt) Ltd. LECO buys Electric Power from CEB.
Generation there exist private companies like Asia Power Station, Yugadanavi Power Station
etc. CEB buys Electric Power from those private sectors when they need it (especially at
the peak hours). But the transmission is only provided by CEB.
Figure 1:2 the Divisions of CEB for Distribution
3
1.5 Organizational Structure of CEB
Figure 1:3 Organizational Structure of CEB
1.6 Electricity Generation
Hydro
Thermal (Oil)
Thermal (Coal)
Wind
Solar
Bio Fuel
4
Table 1-1 Details of Existing Hydro Plants
Plant Name Units x Capacity Capacity (MW)
Canyon 2 x 30 60
Wimalasurendra 2 x 25 50
Old Laxapana 3 x 9.5 + 2x 12.5 53.5
New Laxapana 2 x 58 116
Polpitiya 2 x 37.5 75
Laxapana Total 354.5
Upper Kotmale 2 x 75 150
Victoria 3 x 70 210
Kotmale 3 x 67 201
Randenigala 2 x 61 122
Ukuwela 2 x 20 40
Bowatenna 1 x 40 40
Rantambe 2 x 24.5 49
Mahaweli Total 812
Samanalawewa 2 x 60 120
Kukule 2 x 35 70
Small hydro 20.45
Samanala Total 210.45
Existing Total 1376.95
5
Table 1-2 Details of Existing Thermal Plants
Plant Name Units x Name Plate
Capacity (MW)
Units x Capacity used for
Studies (MW)
Puttalam CPP 3 x 300 3 x 275
Puttalam Coal Total 900 825
Gas turbine (Old) 4 x 20 4 x 16.3
Gas turbine (New) 1 x 115 1 x 113
Combined Cycle 1 x 165 1 x 161
Kelanitissa Total 360 339.2
Diesel 4 x 20 4 x 17.4
Diesel (Ext.) 8 x 10 8 x 8.7
Sapugaskanda Total 160 139.2
UthuruJanani 3 x 8.9 3 x 8.67
Existing Total Thermal 1446.7 1329.4
1.7 Transmission
The transmission voltages in Sri Lanka are 220kV and 132kV. The transmission lines are
connected as a grid and it is called the National Grid. These transmission voltages are stepped
down to the distribution voltages (33kv) at grid substations. The total route length of 220 kV
overhead lines is 501km and total length of 132 kV overhead lines was 1791 km. The
total length of 132 kV U/G lines is 50 km.
1.8 Distribution
The CEB is responsible for 83% of the power distribution in Sri Lanka. The rest is
handled by the LECO. The distribution voltages are 33, 11 kV and 400V. The majority of the
distribution system is overhead and the Colombo city distribution system is designed
using underground cables. The distribution system consists of primary substations and
distribution substations.
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Chapter Two
2 Technical Details
My second industrial training establishment was Ceylon Electricity Board (CEB) and it is well
known electricity service provider in Sri Lanka. Information about worksites that I have worked
during the training period is mentioned in table 2.1 with names of training places and
designations of key training personnel involved and time periods spent in each section.
Table 2-1 Training Schedule of CEB
Training Place Key Training Officer Time Period
From To
Transmission (Operation &
Maintenance) Galle Region
Chief Engineer -
Substation construction &
maintenance
04/01/16 14/01/16
System Control Centre Chief Engineer-System
Operations 18/01/16 22/01/16
Transmission Generation
Planning
Chief Engineer-
Generation Planning 25/01/16 29/01/16
Projects & Heavy Maintenance
– DD4
Electrical Engineer
Projects
01/02/16
12/02/16
Distribution Division -Southern
Province
Chief Engineer -
System Planning engineer
15/02/16
26/02/16
Laxapana Hydro Power
Complex
Chief Engineer-
Laxapana power station
29/02/16
11/03/16
Lakvijaya Power Station
Chief Engineer (Shift in
charge) - Lakvijaya Power
Station
14/03/16
24/03/16
7
2.1 Transmission (Operation & Maintenance) Galle Region
I was assigned to get training at Matara Grid substation under transmission operation &
maintenance. There I could gather knowledge about switchyards of an outdoor grid substation,
protective relays for transmission lines, protection of power transformer, grid substation
operation & maintenance and DC system in the grid substation. Matara Grid Substation (GSS)
has four 132kv lines. They are New Galle 1, New Galle 2, Emblipitiya and Beliatta. The
transmission southern region (Galle region) covers Southern province and some parts of
Sabaragamuwa, Uva and boundaries of western provinces. The southern transmission system
consists of nine 132KV Grid substation (GSS) and interconnected 132KV transmission lines
Most of transmission lines route along thick forests areas. For minimizing line tripping, routine
way leave program is functioned. But line tripping (Automatic switching off) due to lightning
cannot be avoid in some areas. Grid substation maintenance is the most important matter to
provide reliable service. A major challenge is to apply the appropriate maintenance strategy for
GSS so that the organization overall goals and objectives can be attained at minimal cost.
2.1.1 Components of a Grid Substation
A typical grid substation can be dived into three major parts. First one is line bay then
transformer bay and feeder bay. Isolators, circuit Breakers, current transformers and voltage
transformers are common components for above three bays. The main component of a grid
substation is the power transformer. Therefore special protection methods are applied to make
sure safety and reliability of the power transformer. Auxiliary transformer, earthling transformer
is also very important components in a GSS.
Surge arrestors ;
Surges are occurred due to two reasons, Lightning and Switching. If one of surge is
occurred to protect devices surge arrestors are used .The typical surge arrestor has a high
voltage and ground terminal. When surge is occurred the surge current diverted via
arrestor and this occurred due to the semiconducting material (metal oxide) which was
used in arrestor manufacturing.
8
Figure 2:1 Surge arrestor
Voltage Transformer (VT) & Capacitor voltage Transformers (CVT) ;
Both are used to measure voltage of the phases. For metering and protection system
(relays) voltage level was highly important. For that these are used to step down the
voltage to manageable voltage level of electronics components. But in GSS CVT are
commonly used because if VT is used it required higher turn ratio therefore it has higher
unit (equipment) cost. But in CVT first it is used capacitor bridge as a voltage divider
and then divided voltage was stepped down because of this arrangement it become more
reliable and low cost equipment than VT in high voltage power applications.
Figure 2:2 Arrangement of a CVT
9
Current Transformer (CT);
Due to same objective discussed in above point, Current level also important in metering
and protection system. For that CTs were used to step down the current in to manageable
current level to electronic components.
Figure 2:3 Current transformer
Circuit Breakers (CB)
Circuit breaker is an over current protecting device which was used in a GSS and also
can used as a load break switch. CB’s have a moveable contact plates (or male female
contactors) which were driven by spring mechanism. When fault occurred contact was
removed by using the spring charged energy.
10
Figure 2:4 SF6 circuit breaker
When the contactors get removed due to high voltage, arc is generated. To quench this arc
contactors are placed in a neutral medium. According to the medium CB’s are classified. CBs
can be classified as follow,
Figure 2:5 Classification of Circuit Breakers
11
Isolators;
During maintenance or to isolate a bay there should be a visible evidence to make sure
that the phases are not energized. In isolation when the load is breaker by CB’s isolators
are operated to get a visible disconnection of the circuit. Isolators are not a load break
switch so when it is operating should have to make sure that no current will flow across
it. So the procedure of operating an Isolator is, first open the CB, then isolator and finally
earths are connected.
Figure 2:6 Isolator
Power Transformer
Not like in distribution transformers in power transformers protection and cooling is
highly concerned. When transformer operating heat is generated this heat is absorbed by
the inside transformer oil. When the heat is absorbed the oil volume is got increased if
the transformer volume is fixed this may increase the inside pressure therefore a
conservator tank is attached to give the space of oil volume variation. On the other hand
oil must be cooled for that below methods (one or combination) are used.
Table 2-2 Different transformer cooling methods
ONAN Oil natural Air natural
ONAF Oil natural air forced
OFAF Oil forced air forced
ODAF Oil directed air forced
12
Figure 2:7 Power transformer of Matara GSS
Due to aging of insulation materials inside the transformer moisture is formed. To remove that
Dehydrating breather is used. As a protecting mechanism other than used in distribution
transformers another main thing can observed is buchholz relay. It operate when gas (gas
occurred due to short or sparks) occurred in inside the transformer. And also temperature relays
were also included.
Earthling Transformer
Earthing transformer creates a neutral point in a three phase system which provides the
possibility for neutral earthing. Earthing transformer having zig-zag (inter star) winding
is used to achieve the required zero phase impedance stage which provides the possibility
of neutral earthing condition. There is a core type transformer with three limbs. Every
phase winding in zig-zag connection is divided into two equal halves. One halve of
which is wound on one limb and other half is wound on another limb of the core of
transformer
Capacitor banks
Capacitors were primarily used to improve the power factor in the network. The other
benefits are
- Reduced network losses
- Increased voltage stability
- Improved power quality
- Harmonic filter
13
The capacitor banks were connected to the 33 kV (medium voltage) bus bar. Capacitor
banks were shunt connected and it was connected to system via current limiting
inductors.
DC System in the Grid Substation
There are 220V DC and 48V DC battery banks with two chargers and this 220V DC
battery bank is used to control relays, bay equipment and breakers. Other 48V DC
battery bank is used for communication of PLC.
2.1.2 Protection schemes in CEB system
Primary protection (Main Protection)
A Primary protection or the main protection scheme should operate every time when one
of its elements detects a fault. It covers a protection zone made up of one or more of the
elements of the power system such as electrical machines, lines and bus bars.
Secondary protection (Back up Protection)
Back-up protection is meant to operate when for whatever reason, the primary protection
does not work. It should work as a backup for the same equipment for which it is installed
or for the neighboring equipment. Back up protection has to wait a sufficient duration
allowing the main protection to operate.
2.1.3 Distribution Feeder Protection
Figure 2:8 Normal Feeder
14
In here over current & Earth fault protection are used as main protection. For normal outgoing
feeders, these functions are non-directional. In modern substations, these functions are in
cooperated in the controlling IED but in conventional substations they are separate
2.1.4 Transformer Protection
Figure 2:9 Transformer bay
There are two main protection schemes are available. Main one is always the differential
protection and main 2 is restricted earth fault protection (REF). Two REF schemes are available
to cover both windings separately then OC & EF protection are available in both windings as
back up protection. Further to these, stand by earth fault (SBEF) protection is in cooperated in
the LV side. Further to these electrical protection schemes, the transformers are independently
protected by thermal protection.
15
2.1.5 Transmission line protection
Figure 2:10 132 kV Line feeder
Plain OC & EF with delayed time settings than normal feeders avoid tripping of generator for
faults in other feeders. Directional OC & EF is used to establish fast tripping in the own feeder.
Separate VT Is used for voltage measurements. Auto re-closing function is used through a
synchronous-relay.
16
2.2 System Control Centre
Figure 2:11 System Control center
System control center is controlling the whole Sri Lankan electricity system including Power
plants, Grid substations and reservoirs. According to the electricity demand, System control
center commands power plants to connect the system or dispatch from the system. Always
monitor the system frequency, system voltage, amount of Active power and reactive power, and
condition of main breakers. This center communicates with all plants and Grid Substations
especially with frequency controlling machine to keep the system stability. And system control
centre controls only 220kV and 132kV networks.
2.2.1 System Stability Limits
System frequency should be 50 Hz ±1% and main system voltages should be as follows
Table 2-3 System stability limits
System Voltages Required Voltage Limitations
220 kV Between +5% to -5% error range
132kV Between +10% to -10% error range
33kV Between +2% to -2% error range
If the active power demand is greater than the generation power, system frequency decreases
and vice versa. There are system control operators ordering power station to increase their active
power feed to the system. When the voltage drops they adds reactive power to the system.
Victoria, Kotmale, Upper Kotmale, New Laxapana and Samanalawewa operate as frequency
17
control centers of Sri Lankan power system. Hydro plants are taken as frequency control due
to the less responding time and more controllability. Frequency control plant normally operates
at half lord of its capacity. Droops setting at the power plant is changed to frequency control
mood.
2.2.2 System Operation
System operation means the controlling process of whole power system by communicating with
all plants and Grid Substations. This is the task should done by the operation Engineer of the
system control center. Plant connection and dispatching is not a random task. It is done
according to a planning process. There are operational priorities and water usage priorities as
well.
2.2.3 Operational Priorities
Safety of persons
Protection of equipment
Availability of supply
Quality of supply
Economies of system operations
2.2.4 Water Usage Priorities
Water services and drainage
Environment
Irrigation
Power production
In frequency controlling, one plant is set to a different droop setting to response immediately
whereas other plants are set to free governor mode. If the responsible plant is not responding,
other plants will automatically respond.
Spinning reservoir margin is to be not less than 5% of gross generation. Additional available
high cost generation & available hydro plants with short time starting capability may not be
started (for any reason) only to keep this spinning reservoir margin.
The maximum load of any generation unit shall be less than 20% of the total demand. However
for the purpose of maximizing the thermal generation alone, this could be increased to 22.5%.
18
2.2.5 Under-Frequency Load Shedding
Under Frequency Load shading concept is important if suddenly large load connected to system
or if a plant tripped off due to a fault. Then that system becomes unstable at such moment
frequency controlling machine also may not possible to bear the impact. Frequency is decreasing
rapidly. This may cause cascade tripping of generators and may cause total black out, system
can regain the stability by reducing loads from the system. Feeders should cut off automatically
to reduce the load. According to following table feeders are cut-off from breakers
Table 2-4 under frequency load shedding
Frequency (Hz) Load cut-off percentage of the system load
48.75 05%
48.50 10%
48.25 25%
48.00 35%
47.50 45%
2.2.6 Economic Dispatch and Unit Commitment
Thermal power plants should be dispatched according to the merit order.
Unit cost is the cost per 1kwh.
For some thermal power plants, start up or stop or both charges are included.
When calculating the unit cost of hydro plants, water value should be considered.
19
2.3 Transmission and Generation Planning
Generation and transmission planning is very important to generate and transmit sufficient
amount of electricity to satisfy the consumer demand according to the growth demand (National
Power and Energy demand forecast). CEB is the authorized institute in our country to develop
and maintain an efficiently coordinated economical electricity supply system for the country.
According to CEB plans its generation, Transmission and distribution expansions in order to
provide reliable quality electricity to entire country at affordable price.
2.3.1 Generation Planning
There are few considerations when it comes to generation planning, which are
Demand Forecast (25 years)
Existing System modelling
Candidate System
Generation plan is designed for 20 years and & revised at the end of 2 years period. Although
the demand forecast is done for next 25 years, generation plan is designed for 20 years to avoid
the “tail effect”. That means the end values may largely deviate from the actual values. The
planning is based on least cost principle. Demand forecasting is done by categorizing electricity
consumers into 4 sectors (Domestic, Industrial, Commercial, And Other). By identifying the
most suitable linear combination of the parameters of each sector to represent the demand
function. Some parameters are, previous year demand, Gross Domestic Product, Average
Electricity Price, Leading demand, Leading GDP, Population and etc. Population data are
acquired from Senses and Statistical department and GDP is acquired from Central bank. In a
similar manner lost forecast is also done. Then,
Demand Forecast + Loss Forecast = Generation Forecast
Base case plan is published in the long term generation plan & additional cases are considered
when necessary. Additional cases are Fuel cost increase, Government cases, Demand side
management, environmental policies, etc.
WASP software is used for optimization, and Statistical Package for Social Services (SPSS) is
used for load forecast and Stochastic Dual Dynamic Programming (SDDP) is used to calculate
the hydro potential.
20
2.3.2 Preparation of Demand Forecast methodology
Econometric modelling has been adopted by CEB for the electricity demand forecast.
Sales figures of the past were analyzed against following independent variables.
Sector wise Electricity Demand Forecast :
- Domestic Econometric modelling
- Industrial Econometric modelling
- Commercial Econometric modelling
- Other Time Trend
Equation for Econometric Modelling;
Yi = b1+b2X2i+…………. +bkiXki+ ei
Where,
- b₁ = Constant
- Yi = Dependent variable
- Xi = Independent variables
- ei = Error term
Variables used for Econometric modelling
Table 2-5 Variables used for Econometric modelling
Sector Domestic Industrial Commercial Other
Variables
Past Demand, GDP
Per Capita,
GDP, Population,
Avg. Electricity Price,
Previous Year
Demand,
Domestic Consumer
Accounts,
Previous Year Dom.
Consumer Accounts,
Sector wise GDP Per
Capita (Industrial,
Agriculture, Service
Past Demand,
GDP,
Avg. Electricity
Price, Previous
Year Demand,
Previous Year
GDP,
Population,
Sector wise GDP
(Industrial,
Agriculture,
Service)
Past Demand,
GDP,
Avg. Electricity
Price, Previous
Year Demand,
Previous Year
GDP,
Population,
Sector wise GDP
(Industrial,
Agriculture,
Service)
Past
Demand
21
Derive the Regression equations for each sector using SPSS (Statistical Package for
Social Science) software and Statistical tests
Energy Demand Forecast = Domestic Forecast + Industrial Forecast + Commercial
Forecast + Other Forecast
Energy Generation Forecast = Energy Demand Forecast + Total Energy Losses Forecast
Table 2-6 Demand forecast of 2014
Year Demand Growth
Rate
Net*
Losses
Generation Growth
Rate
Peak
(GWh) (%) (%) (GWh) (%) (MW)
2015 11516 4.1% 10.73 12901** 4.5% 2401
2016 12015 4.3% 10.68 13451** 4.3% 2483
2017 12842 6.9% 10.62 14368 6.8% 2631
2018 13726 6.9% 10.57 15348 6.8% 2788
2019 14671 6.9% 10.51 16394 6.8% 2954
2020 15681 6.9% 10.46 17512 6.8% 3131
2021 16465 5.0% 10.40 18376 4.9% 3259
2022 17288 5.0% 10.35 19283 4.9% 3394
2023 18155 5.0% 10.29 20238 5.0% 3534
2024 19069 5.0% 10.23 21243 5.0% 3681
2025 20033 5.1% 10.18 22303 5.0% 3836
2026 21050 5.1% 10.12 23421 5.0% 4014
2027 22125 5.1% 10.07 24601 5.0% 4203
2028 23243 5.1% 10.01 25829 5.0% 4398
2029 24402 5.0% 9.96 27100 4.9% 4599
2030 25598 4.9% 9.90 28410 4.8% 4805
2031 26827 4.8% 9.84 29756 4.7% 5018
2032 28087 4.7% 9.79 31135 4.6% 5235
2033 29395 4.7% 9.73 32565 4.6% 5459
2034 30759 4.6% 9.68 34055 4.6% 5692
2035 32184 4.6% 9.62 35611 4.6% 5934
25 year
Avg Growth
Rate
5.17% 5.10% 4.57%
22
2.3.3 Generation Expansion Planning Methodology
First thing they do is detail planning using SDDP and WASP IV software. In SDDP they concern
about Operating performance of integrated water resources with adequate thermal capacity. And
WASP is used to the economically optimal expansion.
They study parameters are used. They are as followed,
Study Period
- Planning Horizon of 20 years (2015-2034) and study Period of 25 years.
Economic ground rules
- All analyses were performed based on economic (border) prices for
Investments and operations.
- Exchange rate used in the study is 131.55 LKR/USD. (2015 Jan average)
- All costs are based on 1st of January 2015.
Plant Commissioning and Retirement
- It is assumed that the power plants are commissioned or retired at the beginning
of each year
Cost of Energy not served (ENS)
- ENS Cost is estimated as 0.6339 USD/kWh (in 2015 prices). This value has been
derived by escalating the ENS figure given by PUCSL as 0.5 USD/kWh in 2011.
Loss of Load Probability(LOLP)
- According to the Draft Grid Code LOLP maximum value is taken as 1.5%.
Reserve Margin
- Minimum 2.5% & Maximum 20%.
Discount Rate
- 10% discount rate
When this plan is prepared the following assumptions and constrains are used.
All costs are based on economic prices for investment on generating plants. Furthermore,
thermal plants will be dispatched in strict merit order, resulting in the lowest operating
cost.
All plant additions and retirements are carried out at the beginning of the year.
23
Gas Turbine plants can be available only by January 2018. For Gas Turbines, the
construction period is about 1.5 years, but in the absence of any detailed designs for a
power station, it may require 2 years for the pre-construction and construction activities.
2.3.4 Transmission Planning
Transmission planning is required to ensure the reliability of transmission network to match
with load growth and future generation hence estimate the investment required to implement
transmission developments. As mention above the objectives of transmission planning are,
Ensure reliable and stable power system
Estimating the investment
In order to above objectives on transmission network system, they are preparing a Long Term
Transmission Expansion Plan. The key inputs are National Power & Energy Demand Forecast,
Long Term Generation Expansion Plan and Regional medium voltage plan (distribution
regions). Load flow analysis is done to identify the satiability of the system at each year
according to the previous planning.
Transmission plan is designed for 10 years. Growth of the transmission line during first 5 years
is concerned as exponential whereas the last 5 years is considered as linear. Parameters for
transmission line modelling can be listed as follows,
Load data : active power, reactive power, power factor
Generation : capability curve
Lines : inductance, resistance
Solutions For under voltage lines:
Load transferring
Double circuiting the lines
Change the cable type (Ex: zebra -----lynx)
Propose a new grid substation
The transmission planning procedure in simple terms can be described in two stages. The
schematic representation of the transmission planning process is shown below.
24
Figure 2:12 schematic representation of the transmission planning process
At the transmission planning branch, engineers uses power system simulator for engineers
(PSS/E) cad software for load flow analysis. The main objective of transmission planning branch
is to provide electricity which have good power quality and reliability in the present as well as
future.
25
2.4 Projects & Heavy Maintenance – DD4
According to the training schedule I was assigned to Projects and heavy maintenance branch of
region 4, southern zone. And the main duties of this branch are,
Medium voltage tower line construction
Medium voltage tower line maintenance
Primary substation construction
Primary substation maintenance
Maintenance of Gantries , Auto recloses and Boundary meters of the area
Figure 2:13 Sections of the transmission tower
26
There are four types of medium voltage towers available,
Terminal towers (Dead end towers)
Line towers (Suspension towers)
Heavy angle towers (30°<Ɵ<60°)
Medium angle tower (0<Ɵ<30°)
When towers are selected it given a identification code it is done as shown in below,
Figure 2:14 Identification of tower types
Table 2-7 Main tower types
Mast Tower
MSL MDL TSL TDL
MSM MDM TSM TDM
MSH MDH TSH TDH
MST MDT TST TDT
S - Single circuit
D - Double circuit
L - Line
T - Thermal
H - High Angle
M - Medium Angle
27
For medium lines ELM, LYNX and RACOON conductors were used for conductering. In line
construction basically need,
Cable drum
Tensioner
Rubber pulleys
Wrench
Rope
Pilot cable
Swivel joints
Sleeves
2.4.1 Tower Line Maintenance
There is a tower line maintenance procedure.
Hot Line Inspection
Preparing Estimates
Hot line Maintenance
Cold line Maintenance
Hot line maintenance is done when the Medium Voltage (MV) line is energized. Most of
maintenances are normally cold line maintenance. That means workers are working with lines
which have not energized. Several kinds of cold line maintenance are mentioned below.
Replacing of corroded steel parts & stubs.
Replacing of flashover insulators & hardware.
Re-tensioning of conductors.
Re-conductering of conductors.
Repairing of stubs.
Re-concreting of tower foundation
Crimping midspan joints,T- off joints & repair sleeves.
Applying of anticorrosive paint on towers.
Re-fixing of number plate, phase plates etc.
28
2.4.2 Hot line maintenance
Hot line maintenance means maintenance was done in energized transmission lines. When
changing Insulators, Cleaning insulators this method was commonly used. Hot line maintenance
can be divided in to three types
Hot stick method(worker in ground potential and always maintain clearance between
lines to worker)
Bare hand method(Worker was at line potential for that special cloth is required and
always maintain clearance between ground to worker)
Combination of both methods
2.4.3 Cold line maintenance
Cold line maintenance means, maintenance was done without energizing the transmission lines.
Most of the time routing are make like this.
Figure 2:15 CEB workers on a cold line maintenance
2.4.4 Primary Substations (PSS)
Substation is a facility that steps up or steps down the voltage in utility power lines. Voltage is
stepped up where power is sent through long-distance transmission lines. It is stepped down
where the power is to enter local distribution lines. They provide transformation, switching,
protection, sectionalizing, voltage control etc.
In the substation maintenance process, all components should be checked and maintained for
the proper operation of the substation. Power transformer maintenance is very essential for the
protection of transformer
29
2.5 Distribution Division –Southern Province
In Distribution maintenance and construction branch I gained knowledge about construction
procedure, construction materials, poles, earthing system, short term LV expansion plan etc.
And we were appointed to few sections of the branch.Following works are done by the
Distribution Maintenance and Construction section of CEB Southern Province Division.
Situating new pole line
Situating new substation
Transformer maintaining
Identifying tools of line maintenance
2.5.1 Line Support
We call line support for poles here. They must be mechanically strong, they must be light in
weight, they must have least number of parts, and their maintenance cost should be a minimum.
Wooden poles
- There are used when crane cannot be physically access the place we need to
situate the pole. Then this kind of wooden poles are used because men can take
this poles to the place we need.
Steel tubular poles
- Steel tubular poles are more rigid in construction, occupy less space and give to
distribution system a more elegant appearance.
Rain Forced Cement Concrete Poles (RCC)
- In the modern days, these have almost replaced the wooden and steel poles. RCC
poles are costs than the wooden and steel towers.
Pre Stressed Cement Concrete Poles (PCC)
- RCC poles are bulky, heavy and therefore problems in transportation and
handing. To overcome these difficulties PCC poles have been developed.
30
2.5.2 Maintenance Tools and Accessories
At the maintenance unit a chance was given to familiarize with conductors, types of bindings,
H-connectors, sleeves which connect two conductors and tools that they use in their day today
activities by observing them. And also hand experience was given on crimping H-connectors
and how to make a line binding, angle binding and an end binding.
Figure 2:16 D-Complete
Figure 2:17 H-Connector
Figure 2:18 Angle Binding
31
Figure 2:19 End Binding
Figure 2:20 Line Binding
When there is an angle binding or an end binding it is needed to balance the force on the pole.
There are few methods to do that,
Use a Stay (A wire that helps to balance the force on the pole)
Use a Strut (A pole that support for the balance of the pole)
Self-Supported Poles (Supported using a concrete mixture in the hole where the pole is
going to be placed)
32
2.5.3 Transformer maintenance
Figure 2:21 160KVA transformer
Tap changer
- When the supply voltage reduces or rises than 33kV the stepping ratio can be
adjusted using the Tap Changer and then can get the output line to line voltage
as 400V.
Flags
- Tail wires are connected to Flags. Earlier transformers there were no Flags. So
when more connections came to a one point the connections were loose
connected and because of that lots of energy wastages happened.
Pressure release valve
- Controls the pressure inside the Transformer
Bushings
- Stop short circuiting the phases with casing in both primary and secondary sides.
Primary side bushing is small than secondary side.
Arcing Horns
- During a lightning the surges arc in to the earth of the Transformer.
HT
Bushing
s
LT
Bushings
Pressure
release
valve
Tap changer
Flags
33
Transformer Arrangements
- Single pole transformer arrangement
Figure 2:22 Single pole transformer arrangement
- Double pole transformer arrangement
Figure 2:23 Double pole transformer arrangement
34
- Cubical transformer arrangement
In this arrangement Transformer is kept on a cubical which is made of concrete.
Figure 2:24 Cubical transformer arrangement
Earthing arrangements
Figure 2:25 Welded Neutral Earth and Copper Rod
- Neutral of the transformer should be earthed separately
- Earth terminals of surge arrestors, metallic enclosures, supports, metal work and
extraneous metal work not associated with the power supply has to be connected
to a second electrode.
- These two electrodes should be separated at least 3m.
35
Measurement of Resistivity
Figure 2:26 Earth Tester (Megger)
Transformer oil test
In this section we were able to transformer oil insulation test. In order to do that there is a special
machine to do the isolation di-electric test.
Figure 2:27 Insulation oil tester
36
2.6 Laxapana Hydro Power Complex
2.6.1 Introduction
Figure 2:28 Laxapana Complex
Laxapana Complex can be described as Kehelgamu – Maskeli Oya (K-M) complex, because the
five power stations in the Laxapana Complex are situated along Kehelgamu oya and Maskeli
Oya. The main large reservoir at the top of Kehelgamu oya is Castlereagh reservoir, where the
rain water from the catchment area above the reservoir gets collected and the main reservoir
associated with Maskeli oya is Maussakelle reservoir.
Table 2-8 Laxapana Complex details
Plant Name Units x Capacity (MW) Capacity (MW)
Canyon 2 x 30 60
Wimalasurendra 2 x 25 50
Old Laxapana 3 x 9.5 + 2x 12.5 53.5
New Laxapana 2 x 58 116
Polpitiya 2 x 37.5 75
Laxapana Total 354.5
37
2.6.2 Main components of a typical hydro power plant
Figure 2:29 Main components of a typical hydro power plant
Dam
A dam is a huge man made barrier that constructs across the river or stream to disturb
the water flow. And it has got Catchment areas of 8.75 Sq.mls and capacity of 750 ac.ft
and 34 acres of area.
Intake is located near the dam which is the first place where the water taken for
generations which the starting place of the tunnel.
Hydropower Plant
Waterway System Electrical Plant Mechanical Plant
Reservoir
Dam
Intake
Power Tunnel
Surge Chamber
Penstock
Portal Valve Ho use
Generator
Generator Excitation
Automatic Voltage
Regulator (AVR)
Generator Auxiliary Plant
Isolated Phase Bus bar
Generator Transformer
Switch Yard
Fire Protection
Turbine
Main Inlet Valve
Governor
Governor Oil Supply
Cooling & Service
Water system
Drainage &
Dewatering
Compressed Air
System
Air Condition &
Ventilation
38
Pressure Tunnel
Tunnel is made by drilling the earth to bring water to a place where the higher head can
be obtained for maximize the generation. The new Laxapana tunnel has the length of
18500ft while old Laxapana tunnel length is 8400ft. Tunnel are categorized according
to the shape of the cross section.
- Horse shoe type high pressure conditions
- Semi sphere medium pressure conditions
- Circular low pressure conditions
- U shape medium pressure situations
Surge Chamber
- Restricted Orifice
- Simple Shaft
Penstock
Penstocks are high strength steel pipes which can be withstood for water hammer. Penstocks
are located along the higher slop area of which the power plant is designed. New Laxapana
penstock has the length and head of 6200ft and 1775ft respectively.
Water Turbines
Water turbines are used to convert the energy of falling water into mechanical energy. The
principal types of water turbines are:
- Impulse turbine
- Reaction turbine
Old Laxapana has the horizontal axis pelton turbine while New Laxapana has vertical axis pelton
wheel turbine.
Old Laxapana rated Speed – 600 rpm (stage I), 500 rpm (stage II)
New Laxapana rated Speed – 428.5 rpm
39
2.6.3 Electrical System of Laxapana Power Station
Generators
Synchronous generators are installed in most of power station. This synchronous
generators can be categorized as salient pole rotor & cylindrical rotor and normally
salient pole rotor machines are installed in hydro power stations & cylindrical rotor
machines are installed in thermal power stations. Salient pole machines have additional
torque than cylindrical machines as well. And the rotor of synchronous generator is
excited DC supply.
For low speed applications such as hydro plants, salient pole rotor can be seen while for
high speed applications like thermal plants cylindrical rotor is used. Generator
specifications of Old Laxapana (stage I) are shown below.
- Stator connection – Star
- Rotor type – Salient pole
- Rated Power – 10890 KVA
- Rated Voltage – 11 kV
- No. of phases – 3
- Rated Frequency – 50Hz
- Polarity – 10 poles
- Nominal Speed – 600 rpm
- Over speed – 1112 rpm
- Rated Power factor – 0.9
Excitation & AVR
AVR is used to regulate the terminal voltage in a set value. Excitation is increased when
the terminal voltage is decreased. Excitation is given by using a battery bank at the
starting of generator and then it is switched to excitation transformer of the generator
output. The excitation for the rotor field is obtained from transformer rectified by
thyristors and controlled by voltage regulator.
40
Excitation System
The basic function of an excitation system is to provide direct current to the synchronous
machine field winding. Excitation system performs control & protective functions
essential to the satisfactory performance of power system.
- Control functions: Control of voltage & reactive power flow. Enhancement of
system stability
Excitation system is used for creating magnetic field in the rotor of the synchronous
generator. This is very much important part & the excitation system is responsible for
the voltage of the generator. And there are two types of excitation systems basically
available.
- Static excitation system
Figure 2:30 Static Excitation System
- Rotating diode excitation system
Figure 2:31 Brushless Excitation System
41
Laxapana power plant have above two kind of excitation systems with different
generators. Static (brush) excitation system is used for Old Laxapana stage II generators
and Brushless excitation is used for Old Laxapana stage I and New Laxapana all
generators.
Auxiliary Plant
Auxiliary supply means power required for the plant premises for lighting, maintain for
office etc. As a reliability issue, there are three available auxiliary transformers for the
station. The transformer outputs 400 V. In addition there is a stand by auxiliary
transformer and a diesel generator to give station supply if there is an emergency case or
blackout.
Table 2-9 Auxiliary Transformer specifications of O/L and N/L power stations
Specification Old Laxapana New Laxapana
Manufacturer Lanka Transformers ltd UNELEC 1975
Type Oil Immersed Neutral Earthing Oil Immersed Neutral Earthing
Rated power 500kVA 500KVA
Rated voltage 11000/400 V 13125/400 V
Rated current 26.24/721.68 A 23.1/722 A
Vector class Dyn 11 Dyn 1
Type of cooling AN AN
Total weight Round 2200kg 2150kg
Impedance 6.51% 4.1%
Governor
Governor is the load control unit of the machine & this has several functions. Basically
governor shall look after the speed of a generator or turbine system. Ability to start
generator/turbine system to rated speed stably & safely. Governor has main input known
as turbine speed, grid frequency & governor droop settings. Types of governors
- Mechanical governors
- Electro Hydraulic governors. (Speed is sensed by PMG )
- PLC based governors. (Speed measurement using PTs and CTs)
42
Transformers
The power generated by the generators is stepped up to transmission voltage (132kV)
through two three phase 11/132 kV transformers. The tapings of the transformer are
manually operated. The windings are oil cooled and the cooling is classifies as
ONAN/ONAF. As we know transformer is a device which changes one voltage level to
another voltage level. Transformers are categorized according to the purpose and places
where it is being used. Main purposes of use of transformers are voltage step up and step
down, voltage and current sampling, impedance transform.
Figure 2:32 Single phase transformer use in Laxapana Old
43
Table 2-10 Unit Transformer specifications of O/L and N/L power stations
Specification Old Laxapana Stage 01 Old Laxapana Stage 11 New Laxapana
Manufacturer TIRATHAI PUBLIC Le material Electric Alstom
Type of cooling ONAN/ONAF-8/13.33 FOW ONAN/ONAF-15/24
Temperature rise Wdg 55K, Oil 50K Not available Wdg 50K, Oil 40K
Total mass 36 400Kg 26.9T 90508lbs
Rated power 18/24 MVA 16/16MVA 24/24 MVA
Rated voltage 132/√ +/-10%/11 KV 132/√ +/-10%/11 KV 132√ +/10%/12.5KV
Rated current 174.9/1212 A 210/1455A 315/1920A
Highest voltage 145/12 kV 145/12kV 145/13.5
LV/HV 12.5% 9.28% 6.4%
Figure 2:33 Transformer of Old Laxapana power station
44
Switchyard
Old Laxapna switchyard configuration is single breaker and double bus bar system. It
consists of eight lines, bus coupler and three transformers. Line one of all lines are
connected to upper bus bar and line two are connected to lower bus bar. Stage 1
transformer is connected to upper bus bar and Stage 11 transformers are connected to
lower bus bar. New Laxapana switchyard also configured as single breaker and double
bus bar method and it has bus conductors using Zebras conductor. It consists seven lines
and all lines and generators are connected to upper bus bar and lower bus bar is not
energized. Switchyard consists of two bas-bars, current transformer, voltage
transformers, air circuit breakers, SF6 circuit breakers, isolators, earth switches, surge
arrestors etc. The breakers in the switchyard can be connected to each bus-bar. Local
control is also available for emergency and maintenance purposes. A mechanical
interlock system is provided throughout the electrical system.
Figure 2:34 Old Laxapana switchyard arrangement
45
Figure 2:35 New Laxapana switchyard arrangement
Normal Start & Control Sequence of Turbine
Figure 2:36 Normal Start & Control Sequence of a Hydro Turbine
Start Cooling Water Pump
Start HP Lubrication Oil Pump
Start LP Lubricant Oil Pump
Start Governor Oil Pump
Open MIV bypass
Open MIV
Open Governor Valve
Turbine Starts
46
2.7 Lakvijaya Power Station
Lakvijaya power station is the first coal power plant in the country which was commissioned in
2011. It’s a three stage power plants and 300MW is contributed by each stage to make total to
be 900MW.Lakvijaya power plant’s power generation was done by steam turbines. Steam was
generated by burning the coal.
2.7.1 Coal feeding process
Required coal was imported from Indonesia. Then it was stored in the yard which was situated
near to the jetty. From the coal storage coal was sent to coal bunkers by using convey belts.
Figure 2:37 Coal yard and the jetty of the Lakvijaya power plant
These bunkers can store coal which was enough to generate 300MW for 10 hours. From the coal
bunkers coal was fed in to coal mill in there coal was crushed in to powder. This power was fed
in to the furnace. That coal powder must be in 70°C so hot and cold air mixture was used
(Primary air). Required hot air was taken by heating primary air from air pre heaters which were
used heat of the exhaust flue gas. And normal air was used as a cold air. Finally secondary air
was fed in to the furnace for burning.
Figure 2:38 Coal feeding process in the Lakvijaya power plant
47
2.7.2 Coal burning process
Figure 2:39 Flow diagram of coal burning
2.7.3 Primary air and secondary air supply in burning process
Primary air was taken from atmosphere by using two primary air fans (PA fans). This primary
air was used to send coal powder into the furnace. And also primary air was sent through the air
pre heater to increase temperature of it and then hot primary air and cold primary air were mixed
to get required temperature because it will increase efficiency of burning process. Two draft
fans were used to supply secondary air to the furnace as shown in figure 2.39 the main purpose
of secondary air was to supply O2 for coal burning.
2.7.4 Air pre heater
It was an arrangement which was used to exchange the heat in the exhaust flue gas in to primary
and secondary air.
2.7.5 Boiler of the Lakvijaya power station
This is the largest boiler in the Sri Lanka. It’s consists with burners, super heaters, re heaters,
economizer and the air pre heater. The specialty of this boiler was water tube wall is used to
kept water inside the boiler.
48
2.7.6 Bottom ash handling
After the coal burning the remaining solid particles are called bottom ash. Submerged conveyor
belt system is used to collect bottom ash from the furnace.
Figure 2:40 Submerged conveyor belt system which is used to remove bottom ash
2.7.7 Fly ash handling
After the coal was burned the particles which were mixed with flue gas was called fly ash. To
avoid mixing of fly ash with environment special mechanism was used in this plant which was
called as electrostatic precipitator ESP. In ESP positively charged collecting plates were used.
When gas flue gas hit the plats fly ash particles are kept on the collecting plate surface. Time to
time to remove the collected ash plates were discharged and vibrated
2.7.8 SOX and NOX reduction in flue gas
During burning process NO2 and SO2 were formed. To remove SOX (Sulfur oxide SO2)
Absorber was used. Inside the absorber flue gas was sent through the sea water. Inside of the
absorber below chemical reaction was occurred. And SO4-2 is not like SO3
-2 it was dissolved in
water. From that SOX can be removed from flue gas.
SO3-2 + SO2 SO4
-2
To remove NOX (NO2) temperature inside the boiler was maintained in a range of NOX was
not be able to be formed.
49
2.7.9 Electrical details of the plant
Steam generated from coal burning was sent to three steam turbines High pressure turbine (HP
turbine), Low Pressure turbine (LP turbine) and Intermediate turbine (IP turbine).
Generator Ratings
Manufacturer - HEC-China
Type - Cylindrical Rotor Type
Rated Power - 353 MVA
Rated Voltage - 20kV
Rated Current - 10.190 A
Speed - 3000rpm
No of Poles - 2
Excitation Voltage - 364 A
Excitation Current - 2.5kA
One of the uncommon arrangement in this generator was, Hydrogen was used as a coolant to
the Rotor. And purified water (De- ionized water) was used to cool the Stator. HP Turbine, LP
Turbine and IP Turbine were lie on the same shaft to which are directly coupled to the generator
to generate 300MW.
Figure 2:41 Generator and HP, LP and IP of the Lakvijaya power plant
50
Generator Transformer
Plant has 360MVA power transformer to step up 20kV to 220kV. After that power
generated was transmitted to Veyangoda.
2.7.10 Auxiliary systems
Other than above mentioned systems there were some auxiliary systems which were used in the
power generation of the plant. Like,
Lubrication oil system
Lubrication oil cooling system
Hydrogen system
Ventilation system
Sea water treatment plant
Cooling system
51
Chapter Three
3 Management Experience
3.1 Management details
Ceylon Electricity Board (CEB) is administrated by a director Board with a chairman under the
Ministry of Power & Energy. Every subsection I was assigned during my training period was
under the administration of a DGM (Deputy General Manager). Next to the DGM there was the
Chief Engineer (CE). Under the CE there were Electrical Engineers. Under them, there were
Electrical Superintends (ES). All labor gangs are handled by superintendents. Most of the time
Electrical superintends involve with the field work with labors but always they have to get the
approvals and technical advices from the electrical engineers. In CEB, to improve above
collaboration, there are annual get-togethers, trips, ceremonies etc. The inter relationship
between employers and employees is most important for the development of the institute
3.2 Labor Management
Although CEB has a scant- scanty human resource, CEB has managed the working
process to give a more reliable service to the customers. For fulfilling above task CEB has
arranged to provide a congenial environment for the labors, as listed below.
Payment of Bonus
Payment of Incentive against un-availed sick and vacation leave
Payment of special advances for Sinhala/Hindu New Year, Christmas and Ramadan
Festival
Interim allowance of Rs. 1200/=
Long service awards
CEB provident fund
Pension fund
Welfare unit
Sports and recreation
52
3.3 Safety Management
CEB is the most dangerous place for workers. Every year CEB has the record of dead workers
without any confusion. This is not a fault of CEB. The reason for those deaths is disregarding
the safety procedures and lack of concentration while they are working. Most of the time, CEB
has provided every essential, safety components for workers at their every operation to make
sure their safety. But yet they are unable to stop happening those deaths and injuries of labors.
If a worker died by an accident while he is working, CEB must pay the compensation for the
family of the dead worker. So death of a worker is not only a bad reputation for CEB but also a
great loss.
Table 3-1 Effects of Electric Current on the Human Body
53
Life-Threatening Effects
- Currents in excess of a human's "let-go" current (>16 mA at 60 Hz) passing
through the chest can produce collapse, unconsciousness, asphyxia, and even
death.
- Currents (>30 mA at 60 Hz) flowing through the nerve centers that control
breathing can produce respiratory inhibition, which could last long after
interruption of the current.
- Cardiac arrest can be caused by a current greater than or equal to 1 A at 60 Hz
flowing in the region of the heart.
- Relatively high currents (0.25-1 A) can produce fatal damage to the central
nervous system.
- Currents greater than 5 A can produce deep body and organ burns, substantially
raise body temperature, and cause immediate death.
- Serious burns or other complications can cause delayed reactions and even death.
The most dangerous current flow via the chest cavity is through the heart when the shock occurs
in the time relative to the normal heart rhythm. This current may cause ventricular fibrillation,
which is defined as repeated, rapid, uncoordinated contractions of the heart ventricles.
Ventricular fibrillation that alters the heart's normal rhythmic pumping action can be initiated
by a current flow of 75 mA or greater for 5 seconds (5-s) or more through the chest cavity.One
of most common accident in CEB is danger from arcs and blasts. Arcs are the results from the
passage of electric current through air. Then insulation of the air fails but it acts as a conducting
medium for ionized gases. These arcs can reach temperatures up to four times the temperature
of the sun‟s surface. Therefore blasts occur when the metal at the arc site expands and vaporizes.
Hence it is extremely dangerous.
Electrical Maintenance and Repairs
In the case of repairs, only skilled, qualified people should perform those operations. It is too
dangerous when unqualified people perform those repairs without knowing the danger and the
without any experience. When any electrical maintenance or troubleshooting is performed,
sources of electrical energy should be de-energized and all energy sources must be brought to a
54
safe state (capacitors should be discharged and high capacitance elements should be short-
circuited and grounded.)
Difficulties Faced in Electrical Maintenance and Repairs
- Under severe time constraint (Limited time)
- Bad weather conditions
- External Conditions (such as Traffic etc.)
Steps to Overcome those Difficulties
- Proper Planning
- Arrange required materials before the beginning of the work
- Forecasting
- Time Management
- Team Work
Basic Safeguards
- Once hazards have been identified, they must be pointed out and proper steps
must be taken by a qualified person.
- Maintain good housekeeping and cleanliness.
- Resist pressure to “hurry up.”
- Plan and analyze for safety in each step of a project.
- Know and practice applicable emergency procedures.
- Become qualified in cardiopulmonary resuscitation (CPR) and first aid and
maintain current certifications.
- Wear appropriate personal protective equipment.
- Refer to system drawings and perform system walk downs.
- Electrical equipment should be maintained in accordance with the manufactures
instructions.
- Anticipate problems.
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Chapter Four
4 Summary and Conclusions
4.1 Summary
In this report, I tried to describe the experiences and the most important things I learnt during
my training at CEB. In this period I was able to get a good knowledge about new technical things
and also to how to behave at the industry and how to survive at the industry. Also I got a lot of
life experience and learnt how to work with the workers.
During CEB training I have went to seven work places. They are Transmission and Generation
Planning branch, System control center, Project & heavy maintenance – DD4, Distribution
division – southern province, Laxapana Hydro complex, Lakvijaya Power station and
Transmission operation maintenance.
In the first two weeks of my training at Transmission and Operation Matara Grid Substation I
could gather knowledge about transmission network about sri lanka and other main components
about grid substation etc. In the next week I was assigned to train at the system control center. I
learnt about the importance of the system control center and how they dispatch all power plants
in Sri Lanka.In the next week I was assigned to Transmission and generation planning division
I got a valuable knowledge about planning of generation and transmission for future. I
understood the main purpose of this division and how important to the power sector in Sri Lanka.
Next two weeks in my training at the section Projects and Heavy Maintenance – DD4 at
Piliyandala. Here I got an opportunity to visit to a newly constructing 33kV towers at
Thissamaharama.
During next two weeks at distribution maintenance and construction – Southern Province I learnt
about construction and rehabilitation of overhead lines and construction of single and double
pole mounted substations. Then the next two weeks I was trained at Laxapana power station .In
here I leant about synchronizing, starting sequences of generators, maintenances of turbines and
replacing stator of generators, frequency controlling, etc. Last two weeks of my training I spent
at Lakvijaya power station. I got experience about thermal power generating facts etc.
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This industrial training was my second industrial training and as I think I was able to obtain
more practical knowledge from it. I believe that I was successfully completed my second
industrial training.
4.2 Conclusion
Industrial Training at Ceylon Electricity Board as an engineering undergraduate was a very
important, unforgettable period of my life. The industrial training program organized by the
university clearly teaches us how the theoretical knowledge gained at the University is
applicable for the real world appliances before going to the industry as an engineer. This training
helped me a lot to study the responsibilities of workers in each level. At university we always
learnt more theories about existing technologies. From the training I was able to study about the
modern technologies and newer trends in electrical field.
Considering all of these aspects, I can proudly state that the Industrial training I received from
CEB has greatly contributed for the development of my career as an Engineering Undergraduate.
During the three month training period at CEB I was able to gain a vast scope of knowledge
about the electrical field. I experienced the real world practical scenarios from the technical
knowledge I gained. Also I figured out the areas where I could work on to be an effective
Engineer in the industry. Being with all those CEB employees was also a unique experience. I
observed how they achieved their goals through sheer dedication, good management and great
team work which was a fine example to all our trainees to follow if we need to reach our goals
in life. My life was greatly shaped by meeting and working with number of different
personalities and all these experiences I gained would be very valuable, once I go to the industry
as an Engineer.
I sincerely hope that I was able to contribute in an effective way towards achieving the
company’s goals during my stay at CEB. I hope all these knowledge and experiences I gained,
would be useful for my future studies and my career.
Since, I was able to gain more knowledge and practice throughout my training period, which
might be helpful in my future studies as well as the employment; I can recommend Ceylon
Electricity Board as an excellent training institute for engineering undergraduates.
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Abbreviation
AAC - All Aluminum Conductors
ABC - Arial Bundle Conductor
ABS - Air Brake Switch
ACSR - Aluminum Conductor Steel Reinforce
AGM - Additional General Manager
AIS - Air Insulated System
AVR - Auto Voltage Regulator
CB - Circuit Breaker
CE - Chief Engineer
CEB - Ceylon Electrical Board
CSC - Consumer services Center
CT - Current Transformer
CVT - Capacitor Voltage Transformer
DC - Direct current
DDLO - Drop Down Life Off
DGM - Deputy General Manager
EE - Electrical Engineer
ES - Electrical Superintendent
GIS - Gas Insulated System
GM - General Manager
GSs - Grid substation
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HP - High pressure
HRSG - Heat Recovery Steam Generator
HT - High Tension
LBS - Load Break Switch
LECO - Lanka Electricity Company
LP - Low Pressure
LT - Low Tension
NLPS - New Laxapana
OLPS - Old Laxapana Power Station
ONAF - Oil Natural Air Foce
ONAN - Oil Natural Air Natural
PLC - Power Line Carrier
PPM - Programmable Polyphase Meter
RC - Reinforce Concrete
SPS - Sapugaskanda Power Station
VT - Voltage Transformer
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References
Daily diary of my training
Wikipedia
CEB website, http://www.ceb.lk/
Long Term Generation Plan 2015-2034 published by PUCSL
User manual of Laxapana power station.
Maintenance manuals of Lakvijaya power station
