In-Country Training On Operation, Maintenance, Protection & Control of 33/11 kV Substation Project Name: Design, Supply, Installation, Testing & Commissioning of 33/11 kV sub-stations with source end feeder bays.   Contract No: BREB/UREDS/W-01A-001/02/2016-2017 BREB/UREDS/W-01A-002/03/2016-2017 BREB/UREDS/W-01A-004/04/2016-2017

1. Sub-station Maintenance

2. WEL- Maintained

4. Main Equipments in 33 KV Sub-Station
1) Power transformer
2) Circuit breaker
3) Isolator
4) Earthing switch
5) lightning arrestor
6) Busbar
7) Current transformer
8) Potential transformer
9) Protective relay
10) DC battery set
11)Capacitor bank
12)Fire fighting system

5. Power Transformer
Transformer is used to step down the voltage from 33 kV
voltage to 11kv voltage .

6. Maintenance of Transformers
.
Check Earth resistance

7. Check Oil level in main tank & OLTC tank.

8. Check the color of silica gel in breather ;it must be blue in
color .if it is turned pink then recondition it or replace it

9. Check On load Tap Changer Lower/Raise trail by Local & Remote.

10. Trip trail by draining oil in Buchholz relay

11. Tight all connections.
Check breakdown voltage of oil.
Clean the bushings.
Attend the oil leakages
Note Temperature of Oil & leakage

12. Current Transformer

13. Direct measurement of current in high voltage
system is not possible because of insulation problem
of measuring instruments. It is also not possible to
use current flowing through the system directly for
protection purpose due to its high value and high
insulation problem.
Basic functions of current transformers are:
 To reduce the line current to a value which is suitable for
standard measuring instruments, relays, etc.
 To isolate the measuring instruments namely meters, relays,
etc. from high voltage side of an installation.
 To protect measuring instruments against short circuit
currents.
 To sense abnormalities in current and to give current signals
to protective relays to isolate the defective system.

14. CT Earthing
Check the oil level
Oil leakages
Primary injection

15. Potential Transformer
Check the N earthing

16. Basic functions of potential
transformers are:
• To reduce the line voltage to a value
which is suitable for standard measuring
instruments, relays, etc.
• To isolate the measuring instruments,
meters, relays, etc. from high voltage side of
an installation.
• To sense abnormalities in voltage and
give voltage signals to protective relays to
isolate the defective system.

17. Single phase electromagnetic PT is
manufactured in two types:
1. Single Pole ( between lines & earth)
2. Double Pole (between line-to-line)
Energypac ensure quality test facility as to
IEC-76, VDE 0537, ANSI C 57.12 and BS 171
and every transformer are dispatched from the
factory after being tested properly and passing
quality requirements.
Potential Transformer consists of
 Primary and Secondary Windings
 Electromagnetic Core
 Bottom Tank and Oil Expansion Chamber
 Porcelain Bushing

19. Breaker

24. SUBSTATION EARTHING
Easy but most Important!!!!!!!!
Grounding-provided a low impedance path to earth.
Grounding Conductor- A conductor used to connect
equipment or the grounded circuit of a wiring system to a
grounding electrode that normally carry current.
Normally green colour conductor are used for
grounding

25. Substation Grounding-A Great Start !
All metallic components are bonded to earth-
-Breakers
-Transformer
-Structure
-Panels
-lighting shielding
-Relays
-metering equipment
Connect the control room earthing system
with grid

26. Grounding Multi panel

27. 1. Total number of DTs(Distribution Transformer) in the
Division/Sub-division.
2. Monthly DT failure report in each sub-division. A separate
report in a uniformly prescribed format for each DT failure
3. Weekly/Monthly interruption report in a sub-division
4. Monthly record of consumer complaints and records of failure
against each DT.
5. Weekly
leakage of transformer oil.
6. Fortnightly
Oil Level in Transformer.
Operation of cooling fan in
manually and auto mode.
MAINTAINANCE SCHEDULE OF
TRANSFORMER

28. 7. Monthly
Connections (HT & LT terminals)
Explosion vent
Pressure relief device
Watering to earthing Montly
8. Half yearly
Cable boxes, gasket joints .
Bushings .
9. Yearly
Oil in transformer.
Earth resistance.
Oil BDV(Break Down Voltage) test Yearly .
Transformer Input &Out put terminal
tightening Yearly.
Cleaning of transformer.

29. MAINTAINENCE SCHEDULE OF
33KV OUTDOOR BREAKER
 Inspection of the external condition
 checking correct function of position indicators and
interlocks
 Be sure the circuit breaker and its mechanism are
disconnected from all electric power, both high voltage
and control voltage, before it is inspected or repaired.
 After the circuit breaker has been disconnected from the
electrical power, attach the grounding leads properly
before touching any of the circuit breaker parts.

30.  Clean the insulating parts including the bushings.
 See that bolts, nuts, washers, cotter pins, and all
terminal connections are in place and tight.
 After maintenance of circuit breaker must operate the
breaker from local and remote position .

31. MAINTENANCE OF 11KV
SWITCHGEAR
 Proper condition of the switchgear should
be monitored by regular inspections.
 Inspection is primarily to constitute a
visual check for corrosion and moisture.
 Proper mechanical/electrical function of
the following facilities:
switching devices,
interlocking,
protection and signaling facilities