purchase & stores division - ISRO

7.1 Features:
a. Auto trip on earth fault & fuse failure
b. Mechanical tripped on fault indication.
c. Anti-reflex operating handle.
d. LV Pilot cable box and protection compartment. MV cable box to comply in
accordance with EATS 41-26. Modular construction with removable side sheets
on three sides for better access required during installation & maintenance.
Should have fully interlocked cable test access cover.
e. Cast resin encapsulated bus bars in air. Bus chamber to be of extensible version.
f. Flange bolts accordance with EATS 35-1, (or can be fitted with outgoing cable
box).
g. IP55 outdoor enclosure or better version.
7.2 Switchgears operation : Switchgears are to be mounted in such a way its handle
operation shall confirm to per IS 4237
-ON Closing –Clockwise i.e., Vertically upward
-OFF Opening –Anti-clockwise i.e., Vertically down ward
8.0 Vacuum Circuit Breaker: IP 54 Enclosure
a. The unit shall consist of 11KV, 630Amps VCB (for Controlling transformer),
load breaking and fault breaking type fitted with three 630 Amps continuously
rated Vacuum insulated bus bars and arrangement for cable to the primary side
of the transformer.
b. The circuit breaker shall be suitable for manual closing and opening and also for
provision for remote tripping in future.
c. The operating mechanism shall be direct hand operated trip free with a
mechanically operated indicator, positively coupled to the operating mechanism
to indicate whether the breaker is in the closed or in the open position.
d. Voltage Indication: There should be arrangement to check whether the cable
connecting tot the isolator is live or not.
e. The indications for ON/OFF/EARTH of the Isolator & Breaker Switches should
be visible from outside even with the enclosure.
f. Current Transformer: The Ratio of the CTs shall be suitable for Controlling
transformer as specified. The VA burden of the CTs shall be sufficient to
supply the energy required by the relay for normal operation and tripping of the
circuit breaker.
g. Protection System: The protection system should be provided. It must provide
immediate protection and can detect faults instructing the circuit breaker to trip
in less than 40ms.It must have improved operation and Control with the Relay
settings clearly displayed on the front of the panel.
It shall have the provision for the trip test on circuit breaker. The trip inhibit
facility allows the Relay to be tested without tripping the circuit breaker.
Secondary injection can also be carried out using conventional test equipments.
The switchgear and switchboards shall be designed so that the position of the
different devices is visible to the operator on the front of the switchboard and
operations are visible as well.
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