Maintenance schedule of Substation.

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

3. Main Equipments in 33 KV Sub-Station 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

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

5. Maintenance of Transformers . Check Earth resistance

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

7. 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

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

9. Trip trail by draining oil in Buchholz relay

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

11. Current Transformer

12. 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.

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

14. Potential Transformer Check the N earthing

15. 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.

16. 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

17. Breaker

18. 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

19. 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

20. Grounding Multi panel

21. 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

22. 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.

23. MAINTAINENCE SCHEDULE OF 33KV OUTDOOR BREAKER I nspection 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.

24. 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 .

25. 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