Electrical transmission and distribution equipment; Experience in operating, maintaining and troubleshooting of Switchyard and substation equipment
The term “troubleshooting” mainly attributes to non-closure of “closing coil” or “tripping coil” of all circuit breakers or/and all remote operating isolators, therefore, troubleshooting mainly concerns. The d.c. The control system (the source of auxiliary power), for air blast type, sf6 type, and vacuum circuit breakers.
The interconnectivity of the particular circuit including the various interlocking limit switches and relay contacts.
In the air blast type, the pneumatic system including the copper tubing and its end terminations.
Check for simultaneous open & close of slow open & close of main contacts, of circuit breakers and isolators.
Operation & maintenance of switchyard equipment
Eht switchyard /substation being in the primary network of power distribution, it is the most vital nodal point in the network.
Reliability of power distribution greatly depends on these nodes.
It is, therefore, very important to check and enhance the longevity and quality of each item, comprising these nodes (switchyard).
List of major equipment in switchyard/ substation
a) dry type (cast resin type)
b) oil filled type
2. Circuit breakers
a) air blast type ( 33kv, 132kv, 220kv)
b) sf6 type (220kv, 400kv )
c) vaccum type (220kv, 400kv)
3. Power isolaters
a) horizontal double break isolators (33kv,132kv)
b) horizontal centre break isolators (220kv, 400kv)
c) vertical pantograph isolators (220kv, 400kv)
4. Earthing switches
a) remote power operated (220kv, 400kv)
b) local mannual operated(upto 33kv)
5. Galvanised steel lattice structures for beams & columns
6. Steel pipes for equipment support
7. All aluminium clamps & connectors
8. All aluminium bus-bus tubes for main bus
9. Secondary emergency source for providing. Power to the controlling system (battery,
battery charger, dc board)
10. Horizontal isolators with double break (33kv)
11. Vertical isolators with double break type (33kv)
12. Horizontal central break isolators (220kv & 400kv)
13. (220kv/400kv) vertical break pan to graph isolators
14. Sf6 single break circuit breakers (132kv,220kv)
15. Sf6 double break circuit breakers(400kv)
16. Vacuum single break circuit breaker (132kv,220kv)
17. Vacuum d0uble break circuit breaker (400kv)
18. Earthing switches for 400kv hv dc switchyards.
19. Bus post insulators
20. Multicore cts, cvts
21. Wave traps for communication & line protection
22. Switchyard main earthing
23. Switchyard auxiliary earthing for main equipment.
24. Switchyard lighting towers/masts
25. Lightening protection schemes of switchyard
26. 2 no’s of 30 kva ups back to back, with minimum 20 minutes battery back-up. The emergency back-up should be essentially connected to at least 25% of the lighting system of the control room, video conference room, main and half landing of staircases, walking corridor, toilets, flashing exit lights, etc.
Maintain safety of personnel and equipment any cost safety rules should be followed religiously and sequentially to avoid accident/ electrocution.
3.12 i.e. Rules related to safety and minimum clearances to be known before entering a switchyard.
a) for low(230v to 630v) & medium voltage (630v to 11000v) phase to earth…5.8 mtr. Mnm.clearance phase to phase….. Mtr. Mnm. Clearance.
b) for high voltage and extra high voltage phase to earth= 6.1 mtr.mnm.clearance phase to phase….. Mtr. Mnm. clearance
3.13) work permit for attending switchyard/ substation. the issue of work permit/ return of work-permit. This is a very important document and the person who issues/accept it should be a responsible person, not less than the rank of a superintendent engineer from operation & maintenance group.
During carrying out a shutdown operation, the following has to be essentially carried out:
1) switch off the concerned feeders.
2) isolate the feeders.
3) remove and keep the controlling fuses in safe custody.
4) inspect all the accessible bus shutters to be closed and padlocked.
5) issue the work permit, by name of the person who takes it, mentioning all these important activities.
6) apply local earthing by shorting earthing all the phases. After completion of all work, the safety devices and all shootings and earthings are removed and the work permit is returned. Again as a precautionary method, the same person who took the work permit should return it’.
Maintenance of equipment
3.2a) routine maintenance
3.2b) preventive maintenance
3.2c) breakdown maintenance
4.0 annual maintenance contract
Any switchyard being upstream in the load flow diagram, anything and everything in a switchyard, is very critical. An outage due to malfunctioning of any item is disastrous. Like all other equipment, a procedural format is followed by the manufacturers, to generate a list of various parts of all the equipment, erected in a switchyard.
These parts and their sub-parts are codified and identified individually and made compatible with sap.
An inventory of all these items is meticulously maintained so that in the event of an outage, downtime shall be minimum.
4.1 manufacturers’ own AMC
4.2 list of manufacturer/ vendors of EHT equipment applying annual maintenance scheme
4.2a) m/s Siemens India limited
4.2b) m/s ABB
4.2c) m/s Alsthom
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