NATIONAL ALUMINIUM COMPANY LIMITED - Rites

CTs for back up earth fault (51N) as well as for restricted earth fault (64) shall be provided on
the neutral end.
Neutral bushing CT shall be re removable movable at site without opening transformer tank cover/active
part. Secondary leads of 4 sq.mm shall be brought to a weatherproof terminal box and from
there to the marshalling box.
Neutral bushing CTs of suitable ratio, class and adequate burden shall be provided by the
Bidder to cater to the requirement of all standard protection associated with the transformer
of this capacity. CTs for REF shall be PS class.
4.7.8 Marshalling Box
Enclosure mounted marshalling box to be supplied with all controls instruments, protection,
accessories & fitting as required for the transformer and its associated ancillaries. The box
shall be made of 2 mm sheet steel with IP 54 degree of protection.
Sheet heet steel marshalling box of dust dust-proof proof design shall be provided to accommodate
temperature measurement as well as control system, as may be necessary. The box shall be
mounted on the transformer enclosure and shall be provided with internal lighting, spa space
heater and thermostat with their controls accessible from outside.
The box shall be provided with suitable hinged steel doors at the front and all equipment shall
be so placed as to accessible from the front. Provision shall be made for padlocking the doors.
Suitable glazed windows shall be provided at appropriate positions to give an unrestricted
view of the temperature indicators etc, without opening the door.
All initiating tiating “contacts” of shall be wired up to the terminal block in the box. All control wiring
shall be with 1.1kV grade stranded PVC insulated armoured copper cable of 2.5 sq.mm.
Terminal blocks shall have 20% spare capacity.
The external connections betw between een the apparatus on the transformer and the marshalling box
shall be done with suitable heat resisting copper conductor cables of core size not less than
2.5 sq. mm. The cables required to connect the marshalling box and transformer accessories
shall be adequately dequately protected against mechanical damage. There shall be no joints or tappings
between two terminations of any cable. Not more than two terminations shall be made at any
one terminal. All terminations at various devices and terminal blocks shall be pr provided with
plastic ferrules having engraved numbers. All terminals and links shall be so arranged as to
facilitate easy checking and testing of relays, instruments etc. Provision shall be made for
termination of power cables as well as multi multi-core control cables in the marshalling box.
The control circuit terminal blocks provided for external cable connections shall be provided
with screw type terminals and shall be complete with terminal screws, links, cable carries etc,
Each terminal block shall have 20 20% % spare terminals and all wiring shall be such that it is easily
identifiable and accessible for maintenance.
Technical Specification:Sec-6, Electrical
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