In this presentation discuss about Transformer, Sub-station and Maintenance System of Bangladesh Rural Electrification Board (BREB)

1. WELCOME
TO MY PRESENTATION
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2. Presented by
Kawsar Ahmed
ID# 12105297
Program: BSEEE
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3. Presentation on
Power Distribution,
Operation and
Maintenance of
Comilla Palli Bidyut
Samity-1
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4. Contents
 Objectives
 Company Overview
 Classification of Transformers
 Various parts of Transformer
 Power Distribution
 Substation Equipments
 Maintenance
 Recommendation
 Conclusion
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5. Objectives
Observation of rural distribution network
About the system of BREB
About the system of Palli Bidyut Samity
About substation
About transformer
Maintenance system of BREB
The main objective is that how to improve our Socio-
Economic Development by utilizing electricity.
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6. Company Overview
Rural Electrification Board Act, 2013 has been established
instead of Rural Electrification Board Ordinance, 1977 and the
name of Board is Bangladesh Rural Electrification Board
which was responsible for electrifying rural Bangladesh.
Vision
Electricity for all by 2021.
Mission Statement
Provide quality electricity at grass root level in a
democratic manner
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7. Comilla Palli Bidyut Samity-1
Since its inception in 1981, Comilla Palli Bidyut
Samity-1 is playing a vital role in Agricultural,
Industrial and Socio-Economic Development of
Comilla District. It is a consumer owned entity
organized on the basic principles of Co-operative for
distribution of electric power to its members and
operates on No Loss - No Profit basis for the mutual
benefits of all its Members.
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8. Organizational chart of Comilla Palli Bidyut Samity-1
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9. Consumer Information of Comilla PBS-1
Tariff-wise Consumer No (As on December 2014):
Tariff Consumer No. Percentage (%) Cunsumer
Connected in
Current Month
Billed Consumer
Domestic 56500 72.73 206 52362
Commercial 6778 8.72 7 3146
Charitable Institute 1542 1.98 3 1468
Irrigation 6778 8.72 7 3146
General Power 6778 8.72 7 3146
Large Power 2 0 0 2
Street Light 6 0 0 3
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10. Classification of Transformer
According to procedure
According to structure of core
According to application
According to frequency
According to number of phase
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11. Various parts of transformer
 Conservator tank
 Breather
 Buchholz Relay
 Radiator
 Bushing
 Arc horns
 Tap Changer
 Transformer Tank
 Temperature meter
 Oil level indicator
 Name Plate
 Insulating Materials
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12. Conservator Tank
It is transformer oil storage tank and if the main tank oil reduces,
the conservator will feed the oil to main tank.
Its function is to ensure that the transformer tank is completely
filled with oil every time.
Fig: Conservator tank
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13. Breather
It is connected to the conservator tank. It consists of silica gel
material and silica gel absorbs the moisture from the air
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14. Buchholz Relay
Buchholz relay is a safety device
mounted on oil-filled power
transformers equipped with
conservator.
Fig: Buchholz relay
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15. Radiator
Radiators are used in a transformer to cool the transformer oil.
Fig: Radiator
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16. A bushing is the arrangement of insulating material that allows
the terminals of winding to bring out the transformer tank. The
bushing is made of the highest quality of porcelain clad.
Bushing
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17. Arc Horns
Arc horn is a mechanical arrangement of metallic conductor to
perform flashover in a guided way in order to protect bushing.
Fig: Arc horns in the transformer bushing
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18. Tap Changer
Tap changer in a transformer works like a switch, it connects or
disconnects some coil turns of transformer winding so that
voltage will be varied to make specific output.
Fig: Tap changer
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19. Temperature meter
Thermometer is used in transformer to measure the temperature
inside the transformer tank.
Fig: Dial type thermometer.
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20. Oil level indicator
Oil level indicator indicates the oil level of the oil in
conservator tank. Oil level indicator is connected with
conservator tank.
Fig: Oil level indicator
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21. Transformation Ratio
Voltage ratio:
Ep/Es = Np/Ns
Current ratio:
Ep/Es = Is/Ip or EpIp=EsIs
Turns ratio:
Ep/Es=Np/Ns=Is/Ip=a
(a=Transformation Ratio)
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22. Voltage regulation of transformer
The difference between the output voltage at no load
and the output voltage at rated load, divided by the
output voltage at rated load, is called the voltage
regulation of the transformer.
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23. Efficiency of transformer
The output of a transformer is slightly less than the input
because of the losses in the windings and the iron core.
The ratio of the two, expressed as a percentage in the
efficiency of the transformer. The output and input are
expressed in watts or kilo-watts.
Efficiency= Output/Input
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24. Power Distribution System
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25. Equipment of the Substation
Power Transformers
Bus-bar
Insulators
Isolating Switches
Circuit Breaker
Current Transformer (C.T)
Potential Transformer (P.T)
Fuse
Feeder
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26. Substation of Comilla Palli Bidyut Samity-1
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27. Cont.
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28. Circuit Breaker
In Comilla PBS-1 use auto circuit recloser (ACR) instead of
circuit breaker. The rating of this ACR is 360 ampere and
33KV
In this substation use two ACR one in the beginning and other in
the ending point of substation. Both of them use for protection
of the substation equipments though they use it as like switch.
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29. Lightning Arrester
Lightning arrester use for protect from over voltage
generally from thunder. In Comilla PBS-1 lightning
arrester rating is 36KV.
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Fig: lightning arrester

30. CT and PT
Current Transformer (CT) and Potential Transformer
(PT) use for measuring current and voltage in high
voltage and current. If we want to calculate higher
voltage and current directly we will need bigger
measuring instrument which will be higher cost.
For this reason we use CT and PT.
Here Current Transformer (CT) ratio is 600:5
Potential Transformer (PT) ratio is 6350:240
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31. Fuse
A fuse is a short pitch of
metal, inserted in the
circuit, which melts when
excessive current flows
thought it.
Fuse generally use for protect
from over current. In this
substation use drop down
fuse or air break fuse.
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Fig: fuse

32. Fuse characteristic
1. Low melting point.
2. High conductivity.
3. Least deterioration due to oxidation.
4. It carries the normal current without overheating.
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Fig: Fuse on over head line

33. Metering
By the meter we
can measure
present current,
voltage, power
factor and
maximum
current, voltage
etc. There was
analog meter
now they are
using digital
meter.
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Fig: meter

34. Isolator
Isolator is like a switch. It use after the circuit breaker for
ensure line are totally off mode. Mainly it use while
substation or line need maintenance. Isolator has a
manual system for operation.
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Fig: Isolator

35. Power Transformer
Power Transformer is the main part of a substation. In
Comilla PBS-1 use 10MVA power transformer.
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36. Voltage
Regulator
Voltage regulator is a device
which can voltage up or
down in a limitation range
according to consumer
demand. Actually voltage
regulator is an auto
transformer. In Comilla
PBS-1 those transformer we
use they can voltage up or
down up to 10%.
Fig: voltage regulator
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37. Feeder
Distribution feeder circuits are the connections between the
output terminals of a distribution substation and the input
terminals of primary circuits. The distribution feeder
circuit conductors leave the substation from a circuit
breaker. In Comilla PBS-1 have 9 feeders. Every feeder
have own controlling system and also there has a display
which shows maximum current, voltage, power factor and
present current , voltage, power factor and the times its
operation. It shows up to one month data.
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38. Maintenance
Generally Comilla PBS-1
has three type of
maintenance those are:
1. Substation
maintenance
2. Line maintenance
3. Transformer
maintenance
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39. Substation Maintenance
Every time substation needs maintenance if any problem
arises. Without problem substation needs check all
equipment of its quality and condition at least one time in
a year.
For maintenance purpose every time substation has to be
shut down and line has to ground.
First of all we have to check circuit breaker whether it has
any problem or will be any problem. In the time of power
transformer checking it have to be 1000MΩ of insulation
test in megger.
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40. Line Maintenance
There are many types of line maintenance:
Some of maintenance has to be done immediately
which mean whenever problem creates it had to be
solved within four hours. Like over head line tear. For
this type of problem immediately line has to be shut
down.
Some of maintenance can be done within 1-2 days like
transformer problem.
Some of maintenance can be done within a week like
pole or tower got slanted to ground also trees came to
the line.
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41. Transformer Maintenance
In REB have two type of transformer maintenance.
One is single phase transformer and another is power
transformer.
Thy repair single phase transformer in there PBS
workshops. And power transformer repair in central
workshop at Savar in Dhaka. I visited both place and
saw maintenance.
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42. Single phase transformer
If any transformer create problem it bring in the workshop
and the worker see it what type of problem. Workers open
the transformer and take transformer oil into a separate
tank. Then separate every part from the transformer and
mark every part by serial a number.
If any transformer core damage badly which is not possible
to repair those type of transformer rejected totally by
workshop worker.
If any transformer coils damage any other problem thy
repair it.
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43. Cont.
Now I am describing how the worker repairs a single phase
transformer.
After marking transformer every part when they get time to
repair it they take it.
The main part of a transformer is coil binding. In Comilla
PBS-1 they bind coil manually by the worker.
There have two type of coil one is primary coil and another
is secondary coil. Secondary coil strong and hard but
primary coil is thin and weak. That is why secondary coil
normally do not damage. Primary coil damage normally
and need to repair it.
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44. Figure: Coil binding
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45. Figure: complete coil binding
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46. Figure: core binding of transformer
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47. In figure transformer coil into the tank
After binding coil they bind core in transformer then
they keep coil in heat chamber for absorbing moisture
from the coil.
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48. Power transformer
Single phase transformer and power transformer
maintenance procedure are same.
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49. Figure: Power transformer coil
binding in Savar central workshop.
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50. Recommendation
During my internship I came to know that BREB faces lots
of problems and also has some limitations.
Transformer stealing is one of the major problems of
BREB. For this reason transformer with chain and lock
would be better also transformer can be installed in near of
the people house.
 BREB uses 3 single phase transformers for three phase
distribution system which is costly and not efficient. Here
three phase transformer would be more efficient.
Comilla PBS-1 maintains substation manually it can be
error in some time. Here automatic control system or
programmable logic controller would be better and
accurate.
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51. Cont.
Comilla PBS-1 is operated by workers for maintenance
system. Likes winding binding, core binding, core cutting
etc. During my internship I saw a worker cut down his
hand badly by core which is terrible thing. At least in
some specific tasks machine would be superior.
To complete my internship and to understand the technical
terms properly Switchgear and Protective Relays and
Power Station these two courses helped me. So if
someone wants to do internship at BREB, they need to
complete these two courses and stay in BREB’s quarter.
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52. Conclusion
Bangladesh Rural Electrification Board (BREB) has the vast
electricity distribution network all over the country and the
electric power plants are connected with the transmission line
to assure the continuity of electric power. The electric power
plants produce power and feed in to the transmission line. All
power plants are connected parallel with the transmission and
distribution line. BREB is now more developing system day by
day. As the part of this now BREB are using digital meter
instead of analog meter for the consumer. However we have
huge lack of electricity in Bangladesh but all of generation,
grid supply, sub-station, consultancy, local member service of
BREB is more efficient and taking important role to cover lack
of electricity.
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53. Thank you for
your attention
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54. Any Question
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