04-08-2012, 09:54 AM
TECHNICAL SPECIFICATION FOR 245/145/72.5/36 kV ISOLATORS & LINE CUM EARTH SWITCHES
111_Isolator.doc (Size: 230.5 KB / Downloads: 33)
SCOPE:
This specification provides for design, engineering, manufacture, stage testing, inspection and testing before despatch, packing, forwarding and delivery FOR destination of 245 kV, 145 kV 72.5 kV and 36 kV class Isolators and line cum earth switch complete with all fittings, accessories and associated auxiliary equipment mandatory spares which are required for efficient and trouble free operation as specified hereunder.
It is not the intent to specify completely herein all details of the design and construction of equipments. However, the equipment shall conform in all respects to high standards of engineering, design and workmanship and shall be capable of performing in continuous commercial operation upto the Bidder's guarantee acceptable to the Purchaser. The equipment offered shall be complete with all components necessary for its effective and trouble free operation along with associated equipment, interlocks, protection schemes etc., Such components shall be deemed to be within the scope of supply, irrespective of whether those are specially brought out in this specification and/or commercially ordered or not. All similar parts particularly movable ones shall be interchangeable.
OPERATING MECHANISM:
a) Each 245 KV,145 KV, 72.5KV & 36 KV Isolators shall be remote controlled from the control room. Provision shall be made for local motor control also. Operating mechanism shall also be equipped with local manual operating device intended for emergency operation when motor operating mechanism becomes inoperative. Additional electromagnetic type interlock shall be provided so as to prevent the operation of isolator manually or electrically when the corresponding circuit breaker is ON.
b) Manual operating mechanism through crank and reduction gear shall be provided for the earth switch which too will be gang operated. The operation of earth switch which too will be gang operated. The operation of earth switch shall also be electrically inter-locked by providing a 63.5V rated contractor and 220 kV DC rated electro magnet. The contractor will be fed from single phase (132 kV/3/110 kV/3) CVT/ PT provided at the entry of a transmission line in the sub-station. The normally closed contact of said contactor will form part of series chain with other contacts of line isolator/ earth switch to prevent closing of earth switch when the contactor is in picked up position (which means that when the concerned transmission line is live).