Lanka Electicity Company training report - Power distribution

ACKNOWLEDGEMENT

Firstly, I am grateful to Dr. Nayana Alagiyawanna, Dean, Faculty of Engineering,

University of Ruhuna and Dr. Priyankara, Director, Engineering Educational Center,

Faculty of Engineering, University of Ruhuna. Also I take this opportunity to extend

my gratitude to National Apprentice and Industrial Training Authority (NAITA) for

making necessary arrangements to provide me a valuable training period.

Also I am so Indebted to Mr. Bernard Perera, Training Consultant of Lanka

Electricity Company (PVT) LTD & Dr. Narendra Silva, Head of Engineering

Division of Lanka Electricity Company (PVT) LTD for providing us all the facilities

in order to have a valuable training. Next, my sincere gratitude is extended to Mr.

Gajaba Nonis, Electrical Engineer of Lanka Electricity Company (PVT) LTD for

extending us his kind co-operation. I take this opportunity to extend my profound

thanks to the Engineers of Lanka Electricity Company (PVT) LTD.

And Also I am so indebted to Mr. Ravindu Hettiarachhi, Electrical Engineer of GIS

section, for dedicating his valuable time on behalf of our own goodness & for

providing us a faculty of knowledge. Next I am thankful to all the employees of

Nugegoda Branch and Maharagama depot for giving us their kind co-operation.

I take this opportunity to express my profuse thanks to Mr. Lochana Palayangoda,

Accountant of LECO projects, for giving us a huge knowledge on project handling.

And also I’m so thankful to all the Technical officers and Technicians of LECO for

extending their friendly hands towards us. And finally I extend my regards to all the

employees of LECO for all the supports given to have a valuable training.

Thank you!

Wijeweera D.A.P.

RU/E/2007/194

Faculty of Engineering,

University of Ruhuna.

1

PREFACE

This report on industrial training prepared by myself was done so not only as an

exercise to fulfill a part of the training requirements set out by NAITA, but also as a

testimony on the actual industrial training I had. Hereby, a detailed account of my

training programmed at Lanka Electricity Company (PVT) LTD is included.

The idea behind this compilation is that any one going through this report should get a

comprehensive understanding of all technical and management aspects of my training.

In making this a reality, I tried my best to keep to the guidelines stipulated by NAITA.

This is succeeded by my own training experience, which is detailed to the most

possible extent.

This report contains the entire experience and knowledge I’ve achieved from Lanka

Electricity Company (PVT) LTD. The first chapter introduces the company overview

where as the second and third chapters focus on Technical and management

experiences.

I finally hope that this humble and honest effort of mine will meet the expectations of

the University.

2

CONTENTS

ContentsACKNOWLEDGEMENT ............................................................................................. 1

PREFACE ...................................................................................................................... 2

CONTENTS ................................................................................................................... 3

LIST OF TABLES ......................................................................................................... 5

LIST OF FIGURES ........................................................................................................ 6

CHAPTER 1 ................................................................................................................... 7

INTRODUCTION .......................................................................................................... 7

1.1 Overview 7

1.1.1 Lanka Electricity Company (PVT) LTD.......................................................................7

1.1.2 History of LECO........................................................................................................8

1.1.3 Present Status of LECO.............................................................................................9

1.2 LECO Distribution system 10

1.3 The Vision & Mission 12

1.4 LECO Quality Policies 12

1.4.1 Organization Structure of LECO.............................................................................13

CHAPTER 2 ................................................................................................................. 15

Training Experiences - Technical ................................................................................ 15

2.1 Introduction – Training Schedule 15

2.2 11kV Line Equipments 15

2.2.1 Conductors.............................................................................................................15

2.2.2. DDLO, Cut outs & LBC 16

2.2.3 Surge arresters.......................................................................................................18

2.2.4 FDS (Fuse disconnector Switch).............................................................................19

2.2.5 Load Break Switch..................................................................................................19

2.2.6 Auto Reclosers & Sectionalizers.............................................................................20

2.2.7 Transformers..........................................................................................................22

3

2.2.8 CT/PT Unit..............................................................................................................23

2.2.9 Insulators...............................................................................................................24

2.3 Energy Meters 25

2.3.1 Main Components of Induction Type Meters........................................................26

CHAPTER 3 ................................................................................................................. 27

Training Experiences - Management ........................................................................... 27

3.1 Introduction 27

3.2 Construction Manuals and Cost Manuals 27

3.3 PRONTO system 28

3.4 Cost Estimation 29

3.4.1 Cost Estimation Example........................................................................................29

3.5 Tariff & Billing 31

3.5.1 Comparison of Domestic tariff when exceeding 90 units for 30 days....................32

3.5.2 Assignment on Tariff Calculation............................................................................33

3.6 Procurement Procedure 33

3.7 Earthing Procedure (Safety) 34

3.8 Distribution Control Centre 36

3.8.1 DCC Responsibilities...............................................................................................36

3.8.2 Reports Produced By DCC......................................................................................37

3.8.3 System Performance Indices..................................................................................37

CHAPTER 4 ................................................................................................................. 39

SUMMARY & CONCLUSION .................................................................................. 39

4.1 Summary 39

4.2 Conclusion 39

REFERENCES ............................................................................................................. 41

ABBREVIATIONS ...................................................................................................... 42

APPENDIX .................................................................................................................. 44

APPENDIX I ................................................................................................................ 45

4

LIST OF TABLES

Table 1.1 – Customer Service Centers of Branches…………………………… 10

Table 2.1 – Training Locations and durations…………………………………… 15

Table 2.2 – Bare Conductor Sizes and maximum current carrying capacities…… 16

Table 2.3 - Capacities/Full Load Currents/Fuse Ratings in HV Side…………… 23

Table 3.1 – Construction manuals and their Contents………………………… 28

Table 3.2 – Domestic Tariff Rates………………………………………………….30

Table 3.3 – Flow rated domestic tariff table for 33 days………………………… 31

5

LIST OF FIGURES

Figure 1.1 – LECO Logo………………………………………………………….. 07

Figure 1.2 – Branch Locations………………………………………………… 09

Figure 1.3 – Transmission Network of Sri Lanka...…………………………… 10

Figure 1.4 - Distribution Network of LECO…………………………………… 11

Figure 1.5 – Organizational Structure………………………………………………13

Figure2.1 – DDLO in open condition………………………………………………17

Figure 2.2 – LBC with arc chute interrupter……………………………………… 17

Figure 2.3 – inside view of a fuse link…………………………………………….. 17

Figure 2.4 – A Surge arrester……………………………………………………….18

Figure 2.5 – Load Break Switch………………………………………………… 20

Figure 2.6 – Auto Recloser (left) a sectionalizer (right)……………………………20

Figure 2.7 – Auto Recloser & Sectionalizer Arrangement………………………… 21

Figure 2.8 – Internal Structure of a Transformer………………………………… 22

Figure 2.9 – Winding Arrangement (Left) & the Representation of Dyn11……… 23

Figure 2.10 – CT/PT unit…………………………………………………………. 23

Figure 2.11 – Two watt meter method for 3phase 3 wire supply…………………. 24

Figure 2.12 – Pin Post and Tension Disc Insulators (Left to Right)………………..25

Figure 3.1 – Site plan of a proposed bulk substation…………………………….. 30

Figure 3.2 – Procurement Procedure of LECO…………………………………… 34

Figure 3.3 – Earthing Procedure of LECO………………………………………… 35

6

CHAPTER 1

INTRODUCTION

1.1 Overview

As my second compulsory session of industrial training of the Engineering degree

program, I was appointed at Lanka Electricity Company (PVT) LTD. This training

was arranged for 12 weeks from 02-08-2010 to 21-10-2010. During this period I was

assigned in Engineering division, Branch office Nugegoda, Maharagama Depot,

control section and meter test lab and the transformer workshop. This report consists

of the experience & knowledge that I got during the training period.

1.1.1 Lanka Electricity Company (PVT) LTD

Lanka Electricity Company Private Limited (LECO) is a company incorporated in

1983 for the electricity distribution in Sri Lanka. LECO is a government owned

private company which purchases power from Ceylon Electricity Board (CEB) and

distribute to people in the LECO areas. The major goal of founding LECO was to

create a modern and efficient distribution network. In this 27 years, LECO has

successfully reached their target and was able to erect an efficient network all over the

LECO areas. The company has throughout attracted foreign funding from Asian

Development Bank and highly benefited by the consultancies of utility consultants

such as Becca Worely International in setting up their efficient network. LECO as a

utility is benchmarked very high in South East Asian region.

Figure 1.1 – LECO Logo (Source – www.leco.lk)

7

1.1.2 History of LECO

Lanka Electricity Company (PVT) LTD (LECO) is a private limited liability company

registered under the Companies Act No 17 of Sri Lanka for distribution of electricity.

Initially, LECO was founded to answer the problem of voltage drop and to provide a

better reliable supply to the consumers.

Due to the poor management and lack of proper engineering application, local

government authorities failed to maintain their electricity distribution networks with

the rapid growth of urban population. As they were unable to generate sufficient

revenue their dues to Ceylon Electricity Board were not settled properly. All these

resulted in the collapse of the electricity supply system within many local authority

areas. The government, recognizing the weaknesses of Local Authority operations

such as unreliability of supplies, voltage drops, high electrical losses, unsatisfactory

revenue collection procedures as well as a general lack of investment in system

improvements, appointed a presidential Committee to come up with solutions to the

below the issues.

Improving the quality of electricity supply & reduction of electricity wastage.

Improvement of billing, revenue collection and payments to CEB for bulk

purchases and Improvement of quality of management.

Improvement in customer relations, prompt attention to Complaints and

overall efficiency

In 1982,the committee report on the “improvement of Electricity Distribution in

Local Authority areas” having studied several options to overcome problem discussed

above, recommended that formation of an Electricity Distribution Company with

Ceylon Electricity Board participation be the best solution.

As a result of this, LECO was incorporated on the 19 th September; 1983.Present share

holders of LECO are Ceylon electricity Boar, Urban Development Authority,

Government Treasury and four Local Authorities. LECO operates under the direct

supervision of the Ministry of Power and Energy of Sri Lanka and the guidance of

Public Utilities Committee of Sri Lanka

8

1.1.3 Present Status of LECO

Today, the service areas of LECO spread in the costal belt of 4 districts. Though this

is an area with high population density LECO could be able to minimize their losses

up to 6% and it is an extra ordinary achievement of a distribution system of Asian

region as well as south region.

Now LECO launches its operation through 7 branches. They are Negambo,

Nugegoda, Kotte, Moratuwa, Kelaniya,Kaluthara and Galle. Though the LECO area

is very small compare to the area of the country, LECO facilitates more than 15% of

the power distribution.

Figure 1.2 – Branch Locations (Source – www.leco.lk)

9

NUGEGODA BRANCH

Branch Name Customer Service Center

Negambo Negambo, seeduwa, Ja- Ela

Kelaniya Dalugama, Mahara, Kandana, Wattala

Nugegoda Nugegoda, Maharagama, Boralesgamuwa

Moratuwa Moratuwa North, Moratuwa South,

Panadura, Koralawella, Keselwatta

Kotte Pitakotte, Kotikawatta, Kolonnawa

Kalutara Kalutara, Payagala, Aluthgama

Galle Galle, Hikkaduwa, Ambalangoda

Table 1.1 – Customer Service Centers of Branches

At the present, LECO provides following services to consumers.

1. Providing new connection in LECO areas.

2. All type of breakdown maintenance and preventive maintenance.

3. Rehabilitation of the network

4. Providing necessary facilities for maintaining supply line to line voltage in

the region of 400V±6%

5. Maximum reliability with minimum number of interruptions and minimum

number of interrupted consumers.

6. Revenue collection

1.2 LECO Distribution system

LECO uses 11kV sub transmission voltage to transmit power in LECO areas and then

it will step down to 400V to distribute to consumers.

Figure 1.3 – Transmission Network of Sri Lanka

10

11

LECO takes power from the Primary substations, and then the power is transmitted to

LECO areas via 11kV 3 wire feeders which are radially interconnected. So in a case

of an interruption LECO is able to minimize the interrupted customers as the feeders

are interconnected. Then in the load centers, Distribution transformer is kept to step

down the 11kV to 400V and to distribute it to the consumers. The sectionalized

switching regimes at feeders are configured for rapid fault location and isolation. The

11kV feeders are routed mostly along road corridors and other such access routes. The

automatic reclosing and feeder sectionalizing protection regimes implemented on

these feeders are designed to improve supply reliability

1.3 The Vision & Mission

Vision

Enjoy being the light for lives of people through innovative eco-friendly business

Mission

To provide the best energy solutions to the society through continuous innovation

1.4 LECO Quality Policies

The name Lanka Electricity Company (Private) Limited shall stand for

quality, and the company is committed to be the best electricity distributor in

Sri Lanka.

In all process and services, company’s commitment to quality shall be

apparent. This must also be apparent in the way personnel follow and give

instructions, and in the way they apply the Quality System and support it.

LECO Is committed to delight its customers through deployment of a

competent, dedicated and connected staff backed by the latest technology.

Company personnel shall regard the achievement of quality as one of their

most important duties.

LECO is committed to continually improve its environment and ecology

friendly services contributing to the economic, social and cultural

development of Sri Lanka.

12

1.4.1 Organization Structure of LECO

13 Figure 1.5 – Organizational Structure

Figure 1.2- Organization Structure

The academically qualified, committed and trained professionally-oriented Electrical

Engineers and Skilled Electricians dedicated to maintain a satisfied consumer base

always strive to give the maximum service to the consumers. They are dedicating to

assure optimum safety standards in keeping with international standards. The

chairman, Mr. C. J. Haputantri & the General manager, Dr. M.N.Susantha Perera is

dedicating to take LECO toward a quality service.

14

CHAPTER 2

Training Experiences - Technical

2.1 Introduction – Training Schedule

In the 3 months period of my second industrial training I was assigned to Different

places of LECO. This helped me to identify the processes and methods of LECO very

quickly. I was assigned to Engineering Division, Nugegoda Branch office,

Maharagama Depot, System operations, Control Center and the Meter lab. The time

durations which I spent at each location are showed below.

Training Location Time period Duration(Weeks)

Engineering Division 02/08/2010 – 06/08/2010

21/08/2010 – 06/09/02010

4

Nugegoda branch 07/08/2010 – 13/08/2010

13/09/2010 – 24/09/2010

3

Maharagama Depot 14/08/2010 – 20/08/2010 1

System operations +

Control center

27/09/2010 – 18/10/2010 3

Meter test Lab 19/10/2010 – 22/10/2010 1

Table 2.1 – Training Locations and durations

2.2 11kV Line Equipments

2.2.1 Conductors

Most of the times LECO uses bare conductors for the 11kV lines. But in some cases

LECO uses Arial bundled cables and armored cables also according to the situation.

15

Bare Conductors

For the Bare Conductors, LECO uses AAC conductors. Since LECO uses 11kV as a

sub transmission network and span between poles are minimized as LECO area is an

urban area, LECO hardly uses AAAC or ACSR cables. Conductor sizes and their

current ratings ate shown below. (Source – Construction Manual)

Conductor Name Conductor size(mm2) Maximum current rating(A)

Cockroach 250 477

Lynx 175 390

Hornet 150 352

Wasp 100 279

Fly 60 206

Table 2.2 – Bare Conductor Sizes and maximum current carrying capacities

In LECO, Hornet cable is used in the main feeders. When a spur is divided from a

feeder then Wasp cable is used. For further extensions Fly cable is used.

11kV Arial Bundled Cable

The phase wires of ABC cable made with AAC and the messenger wire is made with

either AAAC or ACSR. The insulation of the cable is made with PVC or XLPE. This

cable is used for the 11kV lines which run very close to the multi story buildings or in

the case of inability to maintain the minimum clearance.

11kV Armored Cable

LECO used Armored Cables very rarely. When a line is laid through an urban area

this cable is used. Especially when a line is laid across a railway track an armored

cable is used. The all 3 phases of the cable is inside a single armor.

2.2.2. DDLO, Cut outs & LBC

In electrical distribution, a DDLO is a combination of a fuse and a switch, used in

primary overhead feeder lines and taps to protect step down transformers from current

16

surges and overloads. DDLO together with fuse link provides over current and short

circuit protection.

Figure2.1 – DDLO in open condition

Figure 2.3 – inside view of a fuse link

When a DDLO (Fig 2.1 – Source - HUBBEL Cutouts manual) together used with

arcing chute interrupters it is called as a load break switch. The load break cutout

provides short circuit protection to utility lines with the added feature of a load

breaking function. The LBC (Fig 2.2 – Source - HUBBEL Cutouts manual) is

applicable for transformer and capacitor bank switching or line sectionalizing. LBCs

provide protection from overloads that just melt the fuse link through the maximum

interrupt capacity of the fuse holder. They also provide load break capability through

300 amperes. So if a LBC is located near a primary or grid substations it is essential to

disconnect the power supply before open the LBC.

The fuse link (Fig 2.3 – Source - CHANCE fuse links manual) of DDLO does the

main function of the DDLO. When a fuse is burnt due to some reason, then the wire is

17

Figure 2.2 – LBC with arc chute

interrupter

melt and broken. Then the fuse tube falls down since fuse tube was supported by the

fuse wire. As illustrated in figure 2.4 above, the fuse link has a slow section and a fast

section which are separately operated in over current and short circuit regions.

The slow current-responsive element is made up of a number of components. The

heater coil and the soldered junction are the two primary components. The insulated

strain pin serves to carry the tension exerted when the fuse link is installed in a fuse

cutout, and as a heat conductor to the soldered junction. The ceramic tube serves as a

heat absorber. The heater coil generates heat at a rate which is proportional to the

square of the current. This heat is absorbed by the ceramic material and transmitted to

the soldered junction via the metallic strain pin. When a certain value of current flows

for a specific length of time, sufficient heat is generated and transmitted to the

soldered junction to cause melting of the solder, and the separation of the fuse

link, and the interruption of the circuit.

The fast current-responsive element is constructed like the single element in a

conventional fuse link. Operation of the fuse link in time periods of less than 4

seconds is conventional.

2.2.3 Surge arresters

Surge arresters (Fig. 2.4 – Source - COOPER surge arrester manual) are generally

used for grounding Surges which drops in to transmission lines and protect the circuit

equipments. Surge arresters provide protection against travelling waves, which may

reach the terminal apparatus. The surge arresters or surge diverters provide protection

against such surges. Surge arrester is a protective device, which conducts the high

voltage surges on the power system to the ground.

Figure 2.4 – A Surge arrester

18

The operation of the varistor arrester is typical of gapless metal oxide arresters.

During steady state conditions, line-to-ground voltage is continuously across the

arrester terminals. When over voltages occur, the varistor arrester immediately limits

the overvoltage to the required protective level by conducting only the necessary level

of surge current to earth. Upon passage of the overvoltage condition, the arrester

returns to its initial condition once again, conducting only minimal leakage current.

2.2.4 FDS (Fuse disconnector Switch)

FDS is a set of HRC fuses which uses for the protection of over current and also uses

as a on load switch. When maintenance has to be done in the LV side and if that

maintenance cannot be done without switching of the power, then FDS is used for

switch off the feeder. To switching on and off, a telescope tool is used and to avoid

the arcing on/off action is done quickly.

There are reasons to use HRC fuses in the FDS. HRC stands for “High Rupture

Capacity". This type of fuses normally used where some delay is acceptable for

protecting the system. It has an advantage of current limiting feature. So it is used for

protection of LV feeders which may melt for higher value of current. H.R.C fuses acts

as secondary protecting devices [back up protection]. This type of fuses normally

used where some delay is acceptable for protecting the system. That means this fuse

will not burn out for a current pulse & as a result of this it identifies a fault current &

an inrush current separately. So these fuses are used in series with surge arresters.

2.2.5 Load Break Switch

11kV feeders in LECO are radially interconnected. So in the case of a fault, the fault

can be isolated using the Load Break Switches and hence the number of interrupted

consumers will be minimized. LBS is a switch which is used for on load switching.

So arcing horn are included in LBS. At Present, circuit breakers are used instead of

LBS. By using a handle attached to the pole, the LBS is operated. This handle is made

out of steel and there is a possibility of a fault current flowing across this handle. So

when the handle is operated, the operator should stand up on the earthing mesh which

is commonly grounded with the handle. So in the case of a fault operator will not be

harm as the voltage difference between his arms and legs are zero. However the

operators are always advised to wear HV gloves while operating LBS.

19

Figure 2.5 – Load Break Switch (Source – Google images)

2.2.6 Auto Reclosers & Sectionalizers

Auto reclosers have the facility of to sense over current conditions on phase fault and

earth fault, and interrupt such fault currents and to re-energize the line by reclosing

automatically after a pre determined time delay. If a fault is permanent, the reclose

will lock open after a present number of operations and isolate the faulty

sections .Series coils inside the recloser tank sense fault conditions and trip the

recloser. Closing energy is provided by a high voltage closing solenoid which

simultaneously charges the opening spring in preparation for a tripping operation. The

units are capable of manual operation from ground level by means of an insulated

fiberglass operating stick. Usually in LECO, auto reclosers are mounted in the

beginning of a feeder. But auto reclosers can be mounted on a pole in the middle of a

feeder.

20

Figure 2.6 – Auto Recloser (left) a sectionalizer (right) (Source – Google Images)

Auto recloser can be used either alone or with sectionalizers in series. If an auto

recloser is used alone then it will only be useful to in the case of a temporary failure

(e.g. In the case of a tree branch touching the line). But when sectionalizers use series

with the auto recloser, then it will isolate permanent faults also. Consider figure

below.

Figure 2.7 – Auto Recloser & Sectionalizer Arrangement

Basically a sectionalizer does not have the ability of load breaking. It operates under

no load condition only. The theory is that, it counts the number of interruptions

occurred by the auto recloser. If that number equal to Sectionalizer’s predefined value

of interruptions then it will open the circuit. So a sectionalizer feeds the supply the

power for an area which a fault is most likely to be occurred, then it will have the

minimum tripping frequency. As in the above figure, SZ3 must have the smallest

tripping frequency (say 2) add then SZ5 has a tripping frequency greater than that (say

3).

So when a fault occurs, Auto recloser will be automatically off and all the

sectionalizers count 1. Then AR1 will be switch on again after a predefined time (say

10 seconds). If the fault is still there AR1 will be switch off again and all the

sectionalizers increase their count to 2. 2 is the value that SZ3 is programmed to open

the circuit and it will open the circuit under no load condition. Then AR1 switches on

again and if there is not a fault it stays close. If there is a fault then it will be open

again and same procedure follows until the fault is isolated.

But since LECO area is an urban area and the cost of sectionalizers and auto reclosers

are high , They are used very rarely.

21

2.2.7 Transformers

LECO uses only step down transformers either as distribution sub stations or bulk

substations. At present LECO uses seal type transformers and earlier LECO used

conservator tank type transformers. The distribution transformer and bulk transformer

step down the 11kV to 400V.

Figure 2.8 – Internal Structure of a Transformer (Source – Google Images)

On the core of the transformer, the secondary winding is wounded and on the

secondary winding primary winding is wounded. For each 3 phases there is a set of

winding. In the distribution transformer, the primary winding is delta connected and

the secondary winding is star connected and the neutral has brought out. The vector

group of the transformer is Dyn11. Transformer oil is put inside the transformer to

insulate and to avoid arcing. The transformer oil is on a certain pressure and if the

pressure inside the transformer is increased due to the temperature rise it

automatically adjust the pressure using the pressure release. Normally distribution

transformers have off load tap changers. Tap changers are on primary side to adjust

the secondary voltage and to give the nominal voltage to customer. The tapping

adjustment means the adjusting the turn ration of the transformer and hence the

voltage. Basically there are 5 tap positions and almost all the times LECO keeps tap

position in the 2nd position. In a case of feeder end voltage drops down below the

acceptable limits, LECO normally doesn’t adjust the tap positions. Instead of that new

bulk substation is constructed.

22

Figure 2.9 – Winding Arrangement (Left) & the Representation of Dyn11

Below shows the relevant fuse links for protecting the transformer from HV side.

Table 2.3 - Capacities/Full Load Currents/Fuse Ratings in HV Side

2.2.8 CT/PT Unit

The main purpose of the this unit is reduce current and voltage levels such as

measurable to many kind of electrical equipment such as measuring meters. Two lines

of three phases are gone through the unit while taking these lines as the primary of the

current transformers. The secondary of the CT will reduce the current to be

measurable while voltage is also reduced by a voltage transformer. Then measuring

devices can be measured the load. The other phase of 3 phase line is kept as a

reference since CT/PT unit uses two watt meter method to measure the power.

23

Transformer capacity (kVA) 50 100 160 250 400 630

11kV full load current (A) 2.6 5.2 8.4 13.1 21.0 33.1

Fuse rating (A) 6 10 12 15 30 40/ 50

A B C

a b c n

Primary

Secondary

30

Dyn11

Figure 2.10 – CT/PT unit (Source – Google Images)

To understand the measurement technique of a CT/PT unit, let’s consider the example

below.

Figure 2.11 – Two watt meter method for 3phase 3 wire supply

In W1 meter,

P1 = IR x VRB

In W2 meter,

P2 = IY x VYB

=IY x (VYN - VBN)

By adding above 2 equations,

P = P1 + P2

= IRVRN + IYVYN – VBN (IY + IR)

But IR + IT +IB = 0

So, P = IRVRN + IYVYN+IBVBN

2.2.9 Insulators

Insulators are intended to support or separate electrical conductors without passing

current through themselves. They are made out of dielectric materials as ceramic or

polymer. There are various type of insulators according to their usage. The insulators

commonly used in 11kV system are,

24

1. Pin insulators

2. Post insulators

3. Tension Disc insulators

Pin Insulators – Pin Insulators (Fig 2.12 – source – Google images) are almost

always deployed in the open air, when wet is a major consideration. To combat this

problem, pin insulators feature skirts or wide shells to increase the surface distance

between the conductor and the pin

Post Insulators – Post insulators (Fig 2.12 – source – Google images) are taller than

pin insulators. These are used for construction especially in the coastal areas the

feeder segments likely to be straight.

Tension Disc Insulators – Disc Insulators (Fig 2.12 –source – Google images) are

used in termination and section poles to bare the tension and also used in the deviation

of feeder direction in large angles.

Figure 2.12 – Pin Post and Tension Disc Insulators (Left to Right)

2.3 Energy Meters

LECO have understood properly maintenance of measuring system can act a

important role in their income. So they are maintain a test lab under the Test Engineer

not only that they have the energy meter factory that installed recently at

BANDARAGAMA .Now they are producing electronic meters which has more

accuracy . LECO always make sure to maintain the accuracy of meters between

±2.5%. There are two types of energy meters according to the working principle They

are, .Induction type meters and Electronic meters.

25

2.3.1 Main Components of Induction Type Meters

Current coil

Each phase has a current coil in series with the load. The line that has high current

flaw must have the CTs in accordance .If it is a single phase only have one coil

Pressure (Voltage) coil

Each phase has a voltage coil in parallel with the load. Supply voltage is directly

applied to this coil. One voltage coil is employed in single phase meters whereas three

in 3 phase meters.

Breaking magnet

This is used to control the disk rotation. This is a permanent magnet located closer to

the disc. If it is not a load the disk must not be rotated

Rotating Aluminum disc

According to the fluxes produce by the current and pressure coil ,the disc

rotates .There are two disks in some kWh meters only. Single phase meters have and

most of three phase meters have only one disc. A shaft, worm gear and bearing

surfaces are attached to it with anti-creep holes and timing mark on it.

Mechanical register

Standard type register has five number wheels, light weight and made to rotate

smoothly.

Bearing

Jewel or magnetic bearings are used. The rotating disk is mounted on the

bearing while making free rotation

26

CHAPTER 3

Training Experiences - Management

3.1 Introduction

LECO has a large number of consumers and LECO is obliged to provide their

maximum service to them. For that, they have a proper efficient system, which the

specified targets and goals are defined and the responsibility is clearly divided. So

each and every employee of LECO has set of tasks and he the person who responsible

for that. In this chapter, the administrative and office practices of LECO.

3.2 Construction Manuals and Cost Manuals

Since almost all the details relevant to the LECO are included in these manuals they

can be treated as the bible of LECO. It is essential to explain about Cost manuals and

construction manuals therefore in this chapter.

Most of the duties, procedures, responsibilities, methods, standard approved designs,

and tools are documented to manuals which are called as construction manuals.

Basing those manuals operations are launched. So it is very easy to find any necessary

details by referring these manuals. Each and every person of the LECO staff has the

access of these construction manuals. So when a problem arises they can clear it by

using these manuals. These construction manuals are essential documents to run the

system smoothly. The contents of construction manuals are shown below.

Construction manual volume and

name

Contents

Volume 1

(Design criteria selection of equipment

overhead line construction)

Voltage definitions, circuit definitions,

design philosophy, Clearance parameters,

Equipment specifications, Distribution

27

design symbols etc.

Volume 2

(General Arrangement Drawings)

Arrangement drawings involving

clearances described in volume 1 and

other important details.

Volume 3

(Equipment selection chart)

Sag & tension charts, pole selection

charts, foundation selection charts,

insulator selection charts and cross arm

capability chart.

Volume 4

(Equipment drawings)

Drawings of all the equipments used in

construction process such as cable

cutters, T-offs and terminal lugs etc.

Table 3.1 – Construction manuals and their Contents

Cost manuals are very useful in estimation processes. Cost manuals include,

Material costs of items and their item code

Labour costs for their defined tasks.

Estimated costs for standardised jobs.

By using these cost manuals we can estimate the cost of a project very quickly and it

is very efficient due to minimum errors. Since these cost manuals are updated time to

time there is not any danger of calculating estimates lesser than actual value.

Together these construction manuals and cost manuals are very powerful documents

which highly help to improve the efficiency of the LECO. It is very essential to keep

that type of essential data as documents since all the employees can use these data as a

reference and it improves the efficiency of the whole system.

3.3 PRONTO system

PRONTO is a software which uses in LECO for all type of managerial works. For this

system each person of LECO has the access anywhere in the LECO network by using

their user name and password. But according to the Hierarchical level of the

organization they have certain levels of authorization. PRONTO system is used for,

Cost estimation

Store keeping

Store checking

28

Items ordering

Procurement procedures

Billing

Keeping consumer details

New connection process

Etc.

So we can see it is very useful in almost all the cases.

3.4 Cost Estimation

For the various reasons, LECO have to do various estimations. As examples,

New service connection

Erection of new line,

Providing a bulk supply

Rehabilitations etc.

These estimations typically consists of,

Material cost

Labour cost

Over head cost

Payments to the contractors.

When a cost estimation done using the PRONTO system, it is programmed according

to several kit numbers according to standardized job. (E.g.- For 11kV bare line with

11kV PS poles 1km 60AAC include the kits MKIT045, LKIT014, CKIT024 and

VKIT010) These kits basically divide in to 4 groups. They are,

LKIT- Labour cost

MKIT - Material cost

CKIT – Contractor cost

VKIT – Overhead cost (Variable kit)

So by using both PRONTO system and the cost manuals, we can do the estimations.

3.4.1 Cost Estimation Example

Below shows a sketch of a plan which is drawn to note down the necessary details of

a proposed bulk substation replacing a 3 phase 60A connection

29

Figure 3.1 – Site plan of a proposed bulk substation

The customer already has a 3 phase 60A connection. But he needed to improve it to a

bulk substation. Old connection was taken from the LV line shown in figure. But to

do this task, the existing LV line had to be converted to 11kV+LV line. Below Shows

the necessary steps to be done and the necessary details for the estimation.

40m of LV line have to be converted to 11kV+LV line

If number of poles to be erected is greater than the number of poles which

gives from cost manual then add the cost of additional poles

Cost of 11/500 PS poll, labour cost and cost for the concrete have to be added

for the transformer pole.

Since the cost of LV bundle cable is included in the standardized cost of

11kV+LV line and there is an existing line, the cost of LV bundle cable has to

be deducted.

Add the cost of the 100kVA bulk substation.

30

Cost of 3 phase meter has to be deducted since the existing 3 phase meter will

be returned to stores.

3.5 Tariff & Billing

In the present, LECO & CEB have the same tariff rates effects onwards 1 st of

November 2008. There are several tariff rates for the several categories of consumers.

Basically 2 factors are considered for dividing the consumers among those categories.

They are,

1. Estimated Ampere requirement of the consumer

2. Consumer’s purpose

The present tariff categories using in Sri Lanka are,

1. Domestic purpose

2. Religious purpose

3. General purpose

4. Industrial purpose

5. Hotel purpose

6. Street lighting

See the appendix 1 to study the tariff rates.

Basically LECO has a billing cycle of 30 days and revenue officers visit each and

every consumer and take the meter reading and submit the bill to the consumer.

Tariff category

Domestic Purpose

Unit charge

(Rs/kWh)

Fixed charge

(Rs/month)

up to 30 units per month

in excess of 30 and up to 60 units per month




above 600 units

3

4.7

7.5

16

25

30

60

90

120

180

240

240

Table 3.2 – Domestic Tariff Rates

In the present domestic and religious tariff schemes, there is a large amount of

increasing in the bill, when the 30 days consumption exceeds 90 units. This is a weak

point of this tariff system. It must be highlighted that above all consumption unit

margins are defined for 30 days. In a case of increasing of decreasing of a billing

31

cycle therefore there won’t be harm to the consumer. As a example if the revenue

officer comes after a 33 days then the above tariff table will be flow rated as below.

Tariff category

Domestic Purpose

Unit charge

(Rs/kWh)

Fixed charge

(Rs/month)


in excess of 33 and up to 66 units per 33 days




above 660 units

3

4.7

7.5

16

25

30

60

90

120

180

240

240

Table 3.3 – Flow rated domestic tariff table for 33 days

3.5.1 Comparison of Domestic tariff when exceeding 90 units for 30 days

For 90 units,

Cost For 0 -30 units = 3x30

= Rs.90.00

Cost For 30-60 units = 4.70x30

= Rs.141.00


= Rs.225.00

Fix cost = Rs.120.00

Discount (as no of units<90) = Rs.30.00

Total bill = Rs.546.00

For 91 units,

Cost For 0 -30 units = 3x30

= Rs.90.00


= Rs.141.00


= Rs.225.00

Cost For 90-91 units = 16x1

32

= Rs.16.00

Fuel adjustment charge = 0.3x(90+141+225+16)

= Rs.141.60

Fix cost = Rs.180.00

Total bill = Rs.793.50

Hence we can see that there will be a price difference of Rs.247.50 between 90 units

and 91 units.

3.5.2 Assignment on Tariff Calculation

In the training period we were asked to make a simple tariff calculator to calculate the

bill of a domestic user. The input parameters were the Number of units and the

Number of days of the consumption. Excel coding for above task is shown below.

3.6 Procurement Procedure

Since LECO doesn’t produce any items within the company all necessary items have

to be taken from the outside market. Sometimes it may be local market or sometimes

it may be from the foreign market. LECO provides an essential service to the

customer. So in the case of a breakdown or any failure LECO must have all the

necessary items in their stores in order to take the quickest reaction. So LECO doesn’t

enjoy the lacking of enough stocks. So a minimum re order level is introduced. When

the numbers of items in the stores are lesser than the reorder level, then the necessary

actions must be taken to maintain the stores without lacking of stocks.

There are two ways of buying an item. They are,

1. Calling tenders

33

=IF( (A2/B2)<=1, (A2*3)+(60),

IF((A2/B2)<=2,(B2*3)+((A2-B2)*4.7)+(90),

IF((A2/B2)<=3,(((B2*3)+(B2*4.7)+(A2-(2*B2))*7.5)*1.3)+(120),

IF((A2/B2)<=6,(((B2*3)+(B2*4.7)+(B2*7.5)+(A2-(3*B2))*16)*1.3)+(180),

IF((A2/B2)<=20,(((B2*3)+(B2*4.7)+(B2*7.5)+(3*B2*16)+(A2-(6*B2))*25)*1.3)

+(240),

IF((A2/B2)>20,(((B2*3)+(B2*4.7)+(B2*7.5)+(3*B2*16)+(14*B2*25)+(A2-

(20*B2))*35)*1.3) + (240), “ERROR” ))))))

2. Calling Quotations

Selecting of the process is depending upon the value of the item to be ordered.

Figure 3.2 – Procurement Procedure of LECO

3.7 Earthing Procedure (Safety)

When maintenance is done in HV line, The Line is switched off and earthed from the

2 directions of the line where maintenance is to be done. This is a highly essential

procedure for safety. Earthing is done to protect from,

34

1. Accidental switching on situations

2. Protect from lightning

3. Generator’s generating voltage which accidentally feeds to feeders

Below shows the proper earthing procedure of LECO.

35

Figure 3.3 – Earthing Procedure of LECO

3.8 Distribution Control Centre

Distribution Control Center (DCC) of the LECO plays an important management role

to maintain continuous and reliable power supply throughout and hence to build a

good image about the LECO among the customers. Under these preview DCC

constantly monitors or controls the performance of the entire distribution system and

also the activities of the operational staff involve in operation and maintenance of the

LECO distribution network. DCC staff also assists customers who seek information

and assistance. DCC staff consists of Control Engineer, chief controller and

controllers.

3.8.1 DCC Responsibilities

Direct instructions to the field staff for switching operations. Remote

operation of switchgear and acquisition of data

Alternate supply arrangements for customers during supply outage

Scheduling of power supply for routine maintenance work or constructions

Inform the ordinary customers about the planned power interruptions through

media and bulk supply customers individually.

Issuing the work permit of “permit to work “for the field staff after isolation of

the High Voltage and related terminal equipment and also reversal of the

operation after completion of the work and cancel the work permit

Procurement of new equipment to the LECO distribution system

Monitoring an analysis of the power failures and provide instructions to the

field staff /power dispatcher to the restore power supply without delay.

Accepting and disseminating operational information in the form of daily and

monthly reports

Preparation of daily and monthly outage reports and therein recommendations

for the remedial measures are forwarded to the higher management

Assist customers who seek assistance

Coordinating with CEB during source supply outages and other operational

matters

36

3.8.2 Reports Produced By DCC

Daily Report

Daily report consist of all the interruptions (planned and unplanned failures)

according to the relevant category and all other information such as substation name,

feeder name, outage description, , time off, time on, delay hrs, line section, affected

PSS, CSC.

Monthly Reports

1. Electricity supply outage report

This report consists of performance measurement indices, no. of outages, no.

of consumer hrs, and no. of consumer interruptions, under separate branches and as a

total value. Also all the information about interruptions, failures according to the

category are included. Other than that and loss of sales are mentioned in this report.

2. Consumer service calls report

This report consists of number of service calls, average restoration time per

call in hours, as a total value, branch wise, and CSC wise. Also includes percentage

values of calls to depot (by person, by telephone), calls to DCC, type of fault,

unwarranted calls, and speed of restoration.

3.8.3 System Performance Indices

Below performance indices are calculated for each branch & also for the whole

company monthly. These indices are used to measure the overall performance of the

branch.

SAIDI - System Average Interruption Duration Index

Average total duration of interruption of supply that a consumer experience in the

period,

SAIDI = sum of {no. of interrupted consumers*interruption duration}

Total no. of consumers

SAIFI - System Average Interruption Frequency Index

Average number of interruption of supply that a consumer experience in the period,

37

SAIFI = sum of {no. of interrupted consumers}

Total no. of consumers

CAIDI - Customer Average Interruption Duration Index

Average duration of an interruption of supply for consumers, who experienced an

interruption of supply in the period,

CAIDI=sum of {interrupted consumers*interruption duration}

sum of {interrupted consumers}

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CHAPTER 4

SUMMARY & CONCLUSION

4.1 Summary

In this final industrial training, I was assigned to LECO. LECO is the only private

power distributor in Sri Lanka. LECO region is defined as the coastal area of

Negambo to Galle. LECO provides their service to their consumers through 7

branches. Instead of 33kV network as CEB, LECO uses 11kV network in their area.

Concept of is to increase the reliability and the efficiency through “Large number of

short feeders and large number of distribution substations.”

In order to provide a reliable service o the consumers, LECO has a properly organized

system. Each and every procedure is documented specifically and each and every

hierarchical level has assigned to pre defined tasks. That helps enormously to run the

system smoothly. Construction manuals, cost manuals, safety manuals, Specifications,

procurement procedures, GIS procedures, safety procedures, interruption procedures,

New connection and disconnection procedures, financial delegations, maintenance

procedures, PRONTO system, load flow analysis, load forecasting, etc, all together

help to improve the quality of the service to the customers.

The technological concepts used in LECO are suitable for the modern world. LECO

always make sure to use quality products for their distribution lines in order to assure

the safety and decrease the interruptions. Almost always type tested certified

equipments are used in the system. All these above mentioned things are experienced

by me within the 3 months of my industrial training.

4.2 Conclusion

I’ve got a good opportunity to have my second compulsory session of industrial

training in Lank Electricity Company (PVT) LTD. LECO is the Sri Lanka’s sole

private power distributor in Sri Lanka. LECO is honored ISO quality awards for its

outstanding performance and robust growth in this sector.

39

During this valuable period I was able to take so many experiences about the

distribution network of Sri Lanka and I could be able to collect faculty of knowledge

with in these three months of my industrial training.

Here I should mention that I was able to get a special opportunity to work together

technicians as well as engineers and share their knowledge and experiences. Those

things gave me a really good training as an engineering undergraduate.

Since LECO directly deals with consumers, I could be able to get the knowledge

about how to deal with them. But it would be better if LECO would change their

training schedule a little bit in order to get more practical knowledge on technical side

in the sites etc.

However I had a good training session at LECO with in my final industrial training.

So, it helps me to gain a better experience and work made my training valuable and

successful.

40

REFERENCES

1. http://www.ceb.lk/Tariff/tarrif%202008.htm

2. http://www.hntddl.com/english/abc%20cable01.asp?

gclid=CLy09P2gmaUCFQUb6wodSWphIQ

3. HUBBEL Cutouts (Standard, Linkbreak & Loadbreak)and Cutout-Arrester

Combinations manual

4. CHANCE fuse links manual

5. COOPER surge arrester manual

6. Construction Manuals of LECO

7. Cost Manuals of LECO

41

http://www.hntddl.com/english/abc%20cable01.asp?gclid=CLy09P2gmaUCFQUb6wodSWphIQ

http://www.hntddl.com/english/abc%20cable01.asp?gclid=CLy09P2gmaUCFQUb6wodSWphIQ

http://www.ceb.lk/Tariff/tarrif%202008.htm

ABBREVIATIONS

1. AAAC – All Aluminum Alloy Conductor

2. AAC - All Aluminum Conductor

3. ABC- Areal Bundled Cable

4. ACSR- Aluminum Cable Steel Reinforced

5. AO – Administrative Officer

6. BA – Branch Accountant

7. BE – Branch Engineer

8. BM – Branch Manager

9. BOD – Board of Directors

10. CAIDI – Consumer Average Interruption Duration Index

11. CAIFI - Consumer Average Interruption Frequency Index

12. CEB – Ceylon Electricity Board

13. CSC – Customer Service Center

14. CSS – Customer Service Superintendent

15. DCC – Distribution Control Center

16. DDLO – Drop Down Lift Off

17. EE – Electrical Engineer

18. FA – Financial Accountant

19. FM – Financial Manager

20. GIS – Geographical Information System

21. GM – General Manager

22. GPS – Global Positioning System

23. IA – Internal Auditor

24. LBC – Load Break Cutout

25. LBS – Load Break Switch

26. LECO – Lanka Electricity Company (PVT) LTD

27. MA – Management Accountant

28. P&CE – Planning & Construction Engineer

29. P&SE – Procurement and Supply Engineer

30. PE – Procurement Engineer

42

31. PM – Personnel Manager

32. PSS – Primary Substation

33. PVC – Poly Vinyl Chloride

34. SC – Store Clerk

35. SAIDI - System Average Interruption Duration Index

36. SAIFI - System Average Interruption Frequency Index

37. SDM – System Development Manager

38. SOM – System Operation Manager

39. TO – Technical Officer

40. XLPE – Cross link Poly Ethylene

43

44

APPENDIX

APPENDIX I

Tariff category

Unit

charge

(Rs/kWh)

Fixed

charge

(Rs/month)

Demand

charge

(Rs/kVA)Domestic Purpose

For those who consume -






above 600 units

3

4.7

7.5

16

25

30

60

90

120

180

240

240

Religious Purpose

For those who consume -






above 180 units

2.5

3.7

3.7

9

10

12.5

60

90

90

180

180

240

General Purpose

GP1

GP2

GP3

15

13.8

13.6

240

3000

3000

750

675

Industrial Purpose

I-1

I-2

I-3

10.5

9.3

9.1

240

3000

3000

675

650

45

I-2(TD) peak

off peak

I-3(TD) peak

off peak

24.6

8.4

23

8

3000

3000

650

650

Hotel Purpose

H-1(GP)

H-2(GP)

H-2 (I)

15

13.8

9.3

240

3000

3000

750

675

Fuel Adjustment Charge 30% on all unit charges except DP & RP consumers

consuming less than 90 units per month

* Notice is hereby give in terms of section 52(3) of the Ceylon Electricity Board Act

No. 17 of 1969 that is decided to give a discount of Rs. 30/- for Domestic purpose and

Religious purpose category consumers using electricity less than 90 units per 30 day

billing period with effect from 10th Nov 2008

* The fuel adjustment charge applicable to Industrial Category and Hotel Tariff -

Industrial Category consumers has been exempted of 15% with effect from 1st

January 2009 to 09th November 2009

* Save and except the above, all tariff charges and fees published in the Gazette

Extraordinary of the Democratic Socialist Republic of Sri Lanka No.1572/25 dated

24th October 2008 remain unchanged

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Documents

Lanka Electicity Company training report - Power distribution