2. Overview
Objectives
Bangladesh Power Division Structure
Organizational Overview
33/11 kV DPBS-1 sub-station
Sub-station single line diagram
Sub-station equipments
Sub-station operation
Maintenance of sub-station equipments
Findings
Recommendation
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3. Objectives
• To know about sub-stations
• To learn about assemblage of substation equipments
• Study on switchgear equipments
• Operation of sub-stations
• Maintenance of Sub-stations
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5. Bangladesh’s Power Sector
Generation capacity : 13,179 MW (March 2017)
Power import : 600 MW from India
Highest generation : 9,036 MW (30 June, 2016)
Total consumers : 24.2 million (March 2017)
Transmission line : 10,377 CKT. KM (February 2017)
Distribution line : 3,89,000 km (February 2017)
System loss : 13.10% (June 2016)
Distribution loss : 10.69% (June 2016)
Per capita generation : 407 kwh (August, 2016)
Access to electricity : 80%
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6. Organizational Overview
Rural Electrification Board (REB) is
established in 1978.
13th December 1978, DPBS-1,
started its function.
2nd June 1980, DPBS-1 started its
commercial operation.
Contribute in Agricultural, Industrial
and Socio-Economic Development.
Company Logo
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9. Distribution Substation
The assembly of apparatus is used to change
some characteristic of electric supply.
Its connected with grid
Incoming voltage is 33 kV
Outgoing voltage is 11 kV
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10. Dhaka PBS Substation
Dhaka PBS-1 S/S supply power at
Savar area.
Receive power from Kabirpur and
Savar grid.
Capacity 35 MVA.
There are six feeders.
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12. Substation Equipment's
Instrument Transformers
Power Transformer
Automatic Voltage
Regulator(AVR)
Automatic Circuit Re-
closer(ACR)
Insulator
Lightning Arrester
Bus bar
Isolator
Earth switch
Protective Relay
Auxiliary Transformer.
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13. Instrument Transformers
Instrument transformers is used for measuring and
protection purpose.
Instrument transformers are two types –
1. Current Transformer (C.T.)
2. Potential Transformer (P.T.)
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14. Current Transformer (C.T.)
A current transformer steps down the current.
Used for current measurement.
Step up transformer.
It is connected in series
Specification
Primary 50-100 A
Secondary 5A
Frequency 50 Hz
Weight 75 kg
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15. Potential Transformer (P.T.)
It is used to step down the voltage.
Used for voltage measurement.
Step down transformer.
PT is connected in parallel.
Specification
Primary 6350 V
Secondary 240 V
Frequency 50 Hz
Weight 70 kg
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17. Power Transformer
A power transformer is used for
step-up or step-down the voltage.
Transformer has two winding
namely primary and secondary.
Operate at nearly full load.
power transformer
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18. In DPBS substation three types of transformers
are mainly used.
These are:
– Single Phase Transformer
– Three Phase Transformer
– Auxiliary Transformer
Power Transformer
Single Phase Transformer
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19. specifications
Transformer Type OUT DOOR
Type of Cooling ONAN/ONAF
Rated MVA 5/6.25
Rated KV
HV 33 kV
LV 11 kV
Rated Line Current (amp)
HV 87.5/109.3
LV 249.9/312.4
Vector Group Dyn-1
No of Phase 3
% Impedance HV/LV 6
Standard Frequency 50Hz
Year of Manufacturing 2011
Core and Coil 6800 kg
Tank and Fittings 3600 kg
Mass of Oil 3400 kg
Total Mass 13800 kg
Volume of oil 3542 Liter
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20. Parts of Transformer
Transformer Tank
Conservator
Buchholz Relay
Oil level indicator Buchholz Relay
conservator
Transformer Tank
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Oil Level Indicator
21. Bushing
Breather
Cooling system:
O.N.A.N- Oil Natural Air Natural
O.N.A.F-Oil Natural Air Forced
Parts of Transformer (Cont’d)
Breather
Bushing 21
Cooling system
Bushing
22. Silica Gel
Used for the absorption of
moisture in a transformer.
Blue silica gel is fresh.
Pink silica gel contains
moisture.
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23. Parts of Transformer (Cont’d)
Tap Changer
Oil Temperature Indicator
Winding Temperature Indicator
Tap Changer Oil and Temperature level Indicator
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25. Automatic Voltage Regulators
Used to regulate the
voltage.
It takes the fluctuate
voltage and changes them
into a constant voltage.
Rated power 416.5 kVA
Rated voltage 6350 V
Rated current 656 A
Cooling ONAN
Coil temperature rise 55 ̊C
Oil temperature rise 50 ̊C
Fase number 1
Total weight 2060 kg
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26. Automatic Circuit Re-closer
(ACR)
This device where SF6 gas is used to arc
extinction
There is a interrupter for each line.
Specifications
Operating voltage : 240V AC or
24V DC
Current ratio : 500:1
Rated max voltage : 27 kV
Rated continuous current : 630A
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Control panel
ACR
27. Lightning Arrester
Use to protection of power
system equipment.
Protection against lightning
stroke.
Passed total voltage surges
to the ground.
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Lightning Arrester
28. Bus Bar
An assembly of conductors for collecting electric
power and distributing them to outgoing feeders.
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Bus Bar
29. Isolator
It is also known as
disconnecting switch.
It used to protect the
transformer and other
equipment in the line.
Design to open a circuit
under no load.
Isolator
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Isolator
30. Distribution Transformer
The final voltage transformation in the
electric power distribution system.
Stepping down the voltage used in the
distribution lines to the level used by the
customer.
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31. 11 KV/440 V Power Distribution
System
In power distribution system they use
single phase transformer.
Commonly used 1-φ transformers are
rated as.
5 KVA
10 KVA
15 KVA
25 KVA
37.5 KVA
50 KVA
75 KVA
100 KVA
167 KVA distribution transformer
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32. Transformer Test
In DPBS-1 System they do six type of test
Insulation Test
Continuity Test
Ratio and Polarity Test
No Load Test
Full Load Test
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33. Transformer Test
SL. NO Insulation Test Ratio
1 HT/LT Bushing 1000 + MΩ
2 LT Bushing/Tank 1000 + MΩ
3 LT Bushing/LT Bushing 0
After the Insulation test we get this result
After the Continuity test we get this result
SL. NO Continuity Test Ratio
1. HT Busing / Tank 0
2. LT Bushing/LT Bushing 0
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34. Sl. No Ratio and Polarity Test Ratio
1. Obtained Voltage in (HT) Side 240 Volt.
2. Obtained Voltage in (LT) Side 9.07 Volt.
3. Ratio of HT and LT Side 26.461 Volt.
4. Polarity Additive
After the Ratio and Polarity test we get this result
Sl. No No Load Ratio
1 Applied Voltage in LT Side 240 Volt.
2 Obtained Current 0.26 Amp.
3 Loss 24.12 Watt
Sl. No Full Load Ratio
1 Induce Volts 160.1 Volt.
2 Obtained Current 1.74 Amp.
2 Loss 190 Watt
4 Impedance 2.52%
After the No load and Full load test we get this result
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35. Maintenance of Substation
Daily maintenance:
Make record of power (MW) flow in each hour
Switchgear equipment’s inspection
Load management
Emergency Maintenance:
Emergency maintenance is required when any uncertain hazard is
occurred in the electric system.
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36. Maintenance of Transformer
Steps for power transformer shutdown
CB of the Transformer secondary side open.
CB of the Transformer primary side open.
Isolator opens from both sides.
Grounding switch close from both sides.
Make additional grounding if required.
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37. Transformer Faults and Failures
winding failures due to short
circuits :
– Phase-phase faults,
– Phase-ground,
Core faults :
– Core insulation
failure
Lighting Surge
On-load tap changer failures:
– Mechanical,
– Electrical,
– Short circuit,
– Overheating
Abnormal operating
conditions:
– Over loading,
– Over voltage.
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38. Maintenance of Equipments
Maintenance of Circuit Breaker
• For SF₆ circuit breaker, gas pressure should be checked.
• Leakage of gas should be checked
Maintenance of Conservator
• Oil pressure should be checked.
• Oil leakage should be checked.
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39. Remove all additional or local grounding
Grounding switch open from both sides.
Isolator close from both sides.
Transformer primary side CB close.
Transformer secondary side CB close.
After finish the maintenance work
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40. Protection of Substation
Protection scheme in substation are three parts:
1. Transformer protection scheme.
2. Feeders protection scheme.
3. Bus bar protection scheme.
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41. Findings
1. Most of the distribution transformers are overloaded.
2. Repairing division is slow.
3. System loss is more.
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42. Recommendation
1. More concentration is required to maintain the pricing
mechanism.
2. Number of distribution transformers should be increased.
3. Upgraded switchgear equipment’s are highly required.
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Sustainable And Renewable Energy Development Authority (SREDA)
Electrical Advisor and Chief Electrical Inspector (EA & CEI)
Number of Power Plants: 105 Name of Transmission :Power Grid Company of Bangladesh Ltd. (PGCB)
Name of Distribution: DPDC, DESCO, PBS, Bangladesh Power Development Board (BPDB)
I am working on 33/11 kV substation
pic
Edit
Primary connect in power circuit.
Secondary connect in ammeter
Connection gulo porta hoba
It is a static device which transforms electrical energy from one circuit to another without changing its frequency.