INSTITUTE OF TECHNOLOGY

UNIVERSITY OF MORATUWA

REPORT ON INDUSTRIAL TRAININGAt

CEYLON ELECTRICITY BOARD

Sri Devananda RD,

Piliyandala.

NAME : K.B GONAGALA

REGISTRATION N0 : 10/IT/EE/114

COURSE : NATIONAL DIPLOMA IN TECHNOLOGY

FIELD : ELECTRICAL ENGINEERING TECHNOLOGY

PERIOD : 16 MAY 2013 – 16 JULY 2013

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INDEX

1. INTRODUCTION - 02

2. AREA OFFICE - 03 – 05

3. GRID SUBSTATION - 06 – 11

4. CONSTRUCTION BRANCH - 12 – 15

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INTRODUCTION

The Ceylon Electricity Board (CEB), the largest electricity company in Sri Lanka. It is the major institute in charge of

electricity power in sir lanka.power generation, transmission; distribution and retailing are the major functions

coming under its authority.

During the second two months training I could aware of the facts regarding the functions carried out by Area office,

transmission and maintenance of electricity, grid substations and the construction unit in CEB. In brief during those

two months I gathered more knowledge of the main functions carried out by CEB such as transmission,

distributions and utilizations.

On the other hand I was aware of the accessories used for different types of appliances in CEB. The equipment

using for high tension lines and low tension lines could be identified. The safety precautions and safety equipment

used for the line protection could be clearly understood during these two months.

AREA OFFICE

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Two weeks training in the area office was objected to identify the billing and revenue function, new connection

procedure and testing of electrical installation in buildings, maintenance of LV lines and grid substations and area

setup.

My area office was Kegalle area office coming under central province. The administrative levels are as follow.

DGM (central province)

Chief Area Engineer

Engineer

Engineer Assistant

ES

FUNCTIONS OF AN AREA OFFICE

Maintenance of MV and LV lines.

Providing service mains

Maintenance of transformers

Collecting revenue

Kegalle area office has following consumer service centers

Kegalle CSC

Rambukkana CSC

Moronthota CSC

Thulhiriya CSC

BILLING AND REVENUE

Billing and revenue function is one of the significant function carried out by the area office. It is under the controll of

ES ( Commercial). The billing and revenue branch is responsible fro the following tasks.

Disconcerting services ( if an arias of Rs. 1000 is carried out for 1 month service will be disconnected)

Meter testing (in case of a complaint from a customer or from the meter reader the testing is carried out. If

the error is +/- 2.5 then the meter will be changed)

Meter change

Tariff change ( tariff schemes are changed according to the appliance in the installation)

Account finalizing

The category of consumer is divided according to

Estimated Ampere requirement of the consumer

Consumer’s purpose

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There are different tariff categories existing today in Sri Lanka. They are

Domestic

General purpose

Industrial

Religious

Hotels

Street lamping

BILLING NAD REVENUE PROCEDURE

Data collection (from meters) Data entry (the data is computerized and corrections are done if available)

Deliver to consumers collecting of Bills (handed over to meter readers) Printing of Bills (Kandy DGM office)

CALCUALTION OF MONTHLY BILL

Monthly total bill = (units* charges for unit) + fuel surcharge on charges for units + fixed cost

In electricity bill data that can be used to identify the consumer is printed.

For an example

5 – 20 – R – 026

Central province Kegalle area Rambukkana depot Transformer number

The bulk supply is atken from the places where the load is greater than 42 KVA. So in such places the three phase

supply is given and the power consumption is recored in digital meters. Not like other tariff schemes in bulk supply

the chrges are applted on maximum demand and the units consumed during peak hours, off peak hours and day

time imposing deferent charging rates respectively.

Low and medium voltage line maintenances are also carried out by the area office. That is 33 KV and below

voltages. Mainly the transformer protection is carried out. The safety equipment used for the transformer protection

is DDLO and HRC. The DDLOs are used in the high voltage side and the HRC in the low voltage side.33KV line is

directly connected to the DDLO, a switching device for T/F protection for high currents due to lightening and short

cutting. When a high current passes through the DDLO the fuse inside gets burnt and then it hangs down. So it is

easy to identify whether a DDLO is cut off or not. HRC is also a kind of switching device like DDLO but likes small

box and inside it the fuse is available. Surge arresters are also used in T/F protection in the presence of surges or

lightening.

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DDLO HRC

When a residence is asked for the supply the distance from the T/F is considered. It should be within 1.8km. is

available then the distance is measured along the power line. Then the drawing is setup and the person has to fill

the required form and finally an estimate is prepared for the job to be carried out. when the fees are charged and the

permission is granted then the supply is given to the person required.

The maintenance of LV and MV lines are also carried by are maitanance unit. They uses

A.A.C (fly)

A.A.C (wasp) for LV lines and

Raccoon

Lynx for MV line maintenance

GRID SUBSTATION

After two weeks training in the area office a basic training in a grid substation was carried out to identify the

transmission and operation function in CEB network. Our grid substation was Ukuwela Grid substation near the

Ukuwela power house the first power house we can see under the Mahaweli project.

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The functions of a grid substation are

Step down the voltage (132/33)

Transmission of 132KV or 33KV

The power flow in Ukuwela substation is as follow.

SEQUENCE OF DEVICES AND EQUIPMENTS INSTALLED IN A GRID SUBSTATION

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UKUWELA POWER HOUSE BOWATENNA POWER HOUSE

PALLEKELEHABARANA

1 &2

KIRIBATHKUMBURA

1 & 2

UKUWELA GRID SUBSTATION

Surge arrester Wave trapperCapacitive voltage transformer

(CVT)

IsolatorsCurrent transformerBreakerBus disconnection

132 KV

A grid consists of several sections of this series of equipment. One section like this in a grid is a bay.

Surge arresters are used to protect the grid from sudden surges and over voltages coming along the line. It is connected to the wave trapper in parallel. A surge counter is connected to the arrester to counter the number of surges. The wave trapper is used to filter the communication signal from the load lines.

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Bus disconnection

Bus bar(33)

Wave trapper along with CVT

The CVT and CT are used to measure the voltage and the current of the line respectively. So they are called as measuring transformers. Isolators and the breakers are used to disconnect the line. Isolator works under only the human control while the breaker works automatically and if needed under human control. If there is a short-circuit in the line the breaker would disconnect the line within 3 seconds.

Isolators SF6 gas breakers oil circuit breakers

Bus bars the large conductors that distribute supply to the different bays of the grid. There are 3 bus bars for 3 phases. There may be 1 set of bus bars or more than that. If there are many bus bar sets a “Bus Coupler” is used to connect the bus bars.

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Bus bars

132/33 transformer is the device that steps down the voltage of 132 to 33KV. To maintain the constant 33KV it has many tapings that is automatically changes the primary side if the transformer that is 132KV side. That is called AVR. Since it has many windings to transform the voltage from one voltage to another it dissipates much heat.so we need to cool the windings or the temperature inside goes high and the transformer stops. The cooling is done by the transformer oil. The main tank inside the T/F is stored the oil. When the temperature goes high the fans outside the T/F blow air and cool it. There is a conservation tank to store the additional oil inside the T/F. the bus bbars are connected to the gantry by “ Post type” insulators. One set of metallic bodies that support the BUS bars and the components in a bay is called as gantry.

Since there is no earthling terminal in the transformer an earthling transformer is used to ground the T/F. that is called the earthling T/F. the power necessary for the utilization of the grid is obtained from the auxiliary T/F. the line is then connected to the 33KV bus bars and the same equipment are installed in the at grid also like the 132

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grid. Finally the 33KV lines are connected to the feeders that transmit the power to the transmission line through towers. The main T/F is in favor of an earthing T/F. since the main T/F ‘s primary side is star connected and the secondary side is delta connected the secondary side is needed of a neutral point. The neutral point is gained by earthing on separate terminal of the T/F.

Before loading the T/F it is energized in order to find any faults are available in the bays due to the T/F. it is done by only by energizing the T/F for 24 hours or more. Only if there are no faults then the T/F is loaded. That means the connections in the 33KV side are connected to the T/F.

During the training we got an opportunity to examine a CT test. Before CTs are connected to the grid proper working conditions are examined. It is done by giving a predetermined current level to the primary side of the CT and the output current from the secondary is tested whether to examine the current ratios supplied by the manufacturer are correct. .since a CT has many tapping the same test must be carried out to the each and every tapping. Then a graph of Voltage vs. Current is drawn. The graph is as follows.

The grid substation was going under the remote control when we were training. So we could be familiar with new control panels. The control of a grid substation is two types.

Local operation – control is done by going to the grid. Remote operation – control is done from the control room.

Remoote control operating panels are powered by DC supply. The supply gained from auxiliary T/F is used in AC form and DC form. A portion of the supply gained is passes through a unit called “LVAC switchgear”. In this unit the supply is fed to three sections.

Inverter cubicle - the supply is fed as AC for the AC require equipments such as computers DC DB cubicle - the supply is fed as DC for the control panels Regulator - this portion of supply is used to charge the batteries used in a sudden power

failure

Battery bank

Modern control panels of a bay consist of

Distance protection Bay control unit Backup protection’

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Ethernet switch

Distance protection Bay Control unit

Backup Protection Ethernet Switch

CONSTRUCTION BRANCH - CENTRAL PROVINCE

Functions carried out by the construction unit

Construction of LV lines Construction of MV lines

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Installation of substations

There are different types of accessories used for LV and MV lines. Depending on the voltages that are constructed various components are used for the jobs.

For LV lines we use A.A.C cables for power distribution and ABC. There are two types of A.A.C cables re available.

Fly cables – they carry up to 155A. Its cross section area being 60mm2 and diameter 7/3.4mm.it can undergo ultimate tensile strength up to 1050kg.

Wasp cables – they carry up to 275A while its cross section area being 100mm. its dia 9s 7/6.39mm. It can undergo ultimate tensile strength up to 1660kg.

For the construction of MV lines we use ACSR and AAAC cables. Further two types of ACSR cables are used.

Raccoon 7/4.09mm Lynx 37/2.79mm

There are various types of insulators used in MV and LV lines.

Pin type insulators

Pin type insulators are used in 33KV lines. The pin type is secured to the cross arm on the pole. There is a groove on the upper end of the insulator for housing the conductor. The conductor passes through this groove and it is bound by the annealed wire of the same material or steel binding wire.

Line post insulators

These solid core line post insulators are made of brown galvanized porcelain. They are cooperated with necessary hardware such as steel nut, string washer and 2 no of washers suitable to fix the on the cross bars.

Tension insulators

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They are in disc type and are made of either in porcelain or glass. The hardware part of the disc insulator is cap and pin type assembly with a 16mm ball and socket coupling, Inco operated a locking device.

POLES

There re basically three types of poles available in MV and LV constructions

Terminal poles(dead end poles)

Here the line is terminated with MV tension insulators on one side of the pole.

Shackle poles

Line is terminated with MV tension insulators on both sides of the sale pole

Intermediate poles

Line is continuous and is supported on MV pin insulators or post insulators

Except those poles self-supporting poles are used in the urban area where the stays can’t be installed.

According to the height and the weight they can bear up they can be classified as

8.3 m poles - used in LV lines for 400V

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10 reinforced concrete 300kg - for LV and MV

11m pre stressed poles 350 kg - for intermediate poles

11m pre stressed poles 500 kg - for self-supporting poles in LV and MV

11m pre stressed poles 850 kg - DO

11m pre stressed poles 1200kg - DO

13m pre stressed poles 500 kg - MV double cct poles

13m pre stressed poles 850 kg - MV double cct or MV double cct with LV lines

13m pre stressed poles 1200 kg - MV double cct or MV double cct with LV lines with self-supporting

Stays are used to balance the load on the poles and one pole may content more than one stay. Stay consists of a stay wire, stay assembly, stay and strut bracket, stay insulator and earthing accessory.

INSTALLATION OF SUBSTATION

Installation of substations or the transformers is considered when supplying 400V from 33KV. Depending on the demand on the T/F the planning division determines the appropriate T/F rating for the particular job. There are different methods of placing T/F on poles.

Single pole T/F can only be used up to 160 KVA Double pole T/F place up to 400KVA Plinth type T/F used in urban and places where space is limited.

Procedure of placing T/F

1. Poles are installed based on the place where it is going to be installed2. Fix cross arms to install insulators3. Insulators (pin type) are installed4. Basing plates are fixed on the poles to place the T/F5. Installation of DDLO supporting bar6. Installation of DDLO7. Placing of the T/F8. Surge arresters are fixed on the T/F9. Copper wires are drawn from the 33KV through DDLO to surge arresters10. Connection copper wires to the T/F bushings such that bushings and the surge arrester are in parallel.11. Installation of HCR for the secondary side of the T/F12. Connecting 400V supply conductors to the T/F and attach to the 400 lines13. Earthing of T/F

I could also get the opportunity to observe an occasion of replacing a low KVA rated T/F with high rated KVA T/F.

In such situations the supply is disconnected from the DDLOs and then the surge arresters and earthing conductors are removed from the T/F. connections for the primary side of the T/F is removed from the T/F bushings. Then the T/F is replaced and the removed connections are installed again properly. Finally the DDLOs are connected to the line. Low rated T/Fs have one row of bushings while high rated T/Fs have two bushings. The one we replaced had two rows bushings rated at 850 KVA. At the same time we were taught that to replace a T/F that a particular factory owns a payment has to be made before the job is done.

The name plate data of the T/F replaced with the old one

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