REPAIR and REPLACEMENT and MAINT OF SUB STATION POWER HOUSE 11 KV SWITCHGEAR INCLUDING PREVENTIVE MAINTENANCE OF VCBs, TRANSFORMERS, HT CABLES, PANELS, MCCBs AND OTHER CONNECTED WORKS OF EXTERNAL ELECTRICAL SUPPLY AT NOFRA AREA UNDER GE (NW) NOFRA

Disconnecting, dismantling, repairing/overhauling, reassembling, testing and commissioning of existing indoor, 11 kV, horizontal draw-out type Vacuum Circuit Breaker (VCB) trolley of rupturing capacity 250/350 MVA and current rating 400/630/800 Amps, complete, including removal from its installed position, carrying out complete servicing, refitting in the original position, testing and commissioning, all as specified and as directed by the Engineer-in-Charge. Note: The cost of defective spare parts replaced during repair/overhauling shall be measured and paid separately under the relevant BOQ items.

The scope of work shall include the following: (i) Inspection, servicing and overhauling of the manual/motor-operated spring charging mechanism including checking, cleaning, adjustment and lubrication of the operating mechanism, charging motor, gear assembly, large gear assembly, stop bolt assembly, main shaft interlocking assembly, closing spring assembly, operating cam, motor cut-off limit switch, butterfly switch assembly and all associated moving parts. Application of approved grade multipurpose grease/lubricant for smooth and reliable operation shall be carried out. (ii) Inspection, servicing and testing of OLTC lock/trip-free (OLTLF) assembly (where provided), earth fault release assembly, tripping coil, auxiliary switches, control wiring, terminal connections and complete electrical wiring system, including tightening of all electrical connections and replacement of minor consumables as required. (iii) Cleaning, inspection and overhauling of epoxy/support insulators and vacuum interrupters using approved electrical contact cleaner/carbon cleaning solution. Cleaning of all primary and secondary contacts and application of approved conductive graphite/contact lubricant on contact surfaces to minimise oxidation and carbon deposition, ensuring proper electrical continuity.

(iv) Reassembly of all dismantled components, alignment and adjustment of the complete operating mechanism, checking of mechanical and electrical interlocks, functional operation of the breaker, insulation resistance (IR) test using 5 kV megger before and after servicing, High Voltage (HV) withstand test as per relevant IS/IEC standards, operational testing including closing and tripping operations, and commissioning complete, ensuring satisfactory performance in all respects.

Material & labour for Preparation and painting of existing indoor 11 kV, 250/350 MVA, 400/630/800 Amps HT Vacuum Circuit Breaker (VCB) panel/trolley by thoroughly cleaning, scraping, removing rust, old loose paint, dust and grease, filling minor surface imperfections with approved metal filler/putty, applying one coat of red oxide zinc chromate primer, followed by one coat of synthetic enamel paint of shade as directed by the Engineer-in-Charge, to both internal and external exposed metallic surfaces, all as specified and as directed by the Engineer-in-Charge

Material and labour for opening the bus-bar chamber, Current Transformer (CT) chamber, Potential Transformer (PT) chamber and metering chamber of existing 11 kV HT switchboard/panel, carrying out complete inspection, cleaning, servicing, overhauling, testing and reassembly, complete, all as specified and as directed by the Engineer-in-Charge. Note: The cost of defective spare parts replaced during servicing/overhauling shall be measured and paid separately under the relevant BOQ items.

The scope of work shall include the following: (i) Opening the bus-bar chamber and carrying out complete inspection, cleaning and servicing of bus bars, spout insulators, support insulators, space heaters and associated components. Removal of accumulated dust using vacuum cleaner/air blower and removal of moisture using hot air blower. Checking and tightening of all bus-bar joints, terminal connections and insulator mountings. Re-insulation of exposed bus-bar joints using approved insulation compound (STRIPPEX-A & STRIPPEX-B or equivalent), HT insulating tape and approved insulating materials wherever required. Carrying out insulation resistance (IR) test using 5 kV megger before and after servicing, followed by High Voltage (DC) withstand test, complete. (ii) Opening the CT/PT chamber and carrying out complete inspection, cleaning and servicing of Current Transformers (CTs), Potential Transformers (PTs), bus bars, spout/support insulators, space heaters, secondary wiring, terminal blocks and associated components. Removing dust using vacuum cleaner/air blower and moisture using hot air blower. Checking and tightening of all electrical connections. Applying approved anti-tracking insulating coating on CTs and insulators, and re-insulating exposed joints with approved HT insulating tape wherever required, complete. (iii) Opening the metering chamber and carrying out complete inspection, cleaning and servicing of all metering equipment including multifunction/energy meters, indicating instruments, selector switches, control fuses, terminal blocks, relays (where provided), complete control wiring and associated accessories. Removing dust using vacuum cleaner/air blower and moisture using hot air blower. Checking, tightening and testing of all wiring connections, terminals and control circuits, ensuring satisfactory operation of the complete metering system, complete.

Material & Labour for Overhauling, calibration, setting, testing and secondary injection testing of Over Current (O/C) and Earth Fault (E/F) protection relay/release by injecting simulated current through a secondary injection test kit, checking operation at each multiple current setting, verifying pick-up value, time-current characteristics, relay calibration, tripping operation and readjustment of relay settings wherever required, complete, all as specified and as directed by the Engineer-in-Charge.

Material & Labour for Carrying out primary injection testing of Over Current (O/C) and Earth Fault (E/F) protection system by injecting artificial load/current through Current Transformers (CTs), checking operation of the relay at each multiple current setting, verifying CT polarity, relay tripping, ammeter indication, selector switch operation, complete protection circuit, wiring continuity and overall functional performance of the protection system, complete, all as specified and as directed by the Engineer-in-Charge.

Dismantling and overhauling and testing Potential transformer capacity 11 KV / 110 volts AC and replacement of worn out spares such as contacts, bushing, control wiring fibre plates, gaskets , transformer oil and applying multi grease to the mechenical parts & dry graphite conductive sealant to contacts etc & re-assembling the same and commissioning complete all as specified and directed by Engineer-in-Charge. (Note : Spare parts and oil will be measured and paid seperately)

Supply and fixing in repair of transformer breather with 500 grams indicating silica gel, suitable for indoor type oil-filled distribution transformer of capacity 250 kVA to 750 kVA, including filling with fresh silica gel, making all connections, topping up breather oil (where applicable), and testing for satisfactory operation, complete, all as specified and as directed by the Engineer-in-Charge.