remote control equipment - Indian Railways Institute of Electrical ...

5.8.5 Other protective devices
The transformer as supplied by the purchaser will be fitted with following warning and
protective devices.
i) Low oil level alarm.
ii) Buchholz relay with alarm and trip contact.
iii) Oil temperature indicator with alarm and trip contact
iv) Winding tempreature indicator with alarm and trip contact
These contact shall be wired up to a weather proof terminal box mounted on the transformer
by the transformer manufacturer .The connection shall be extended to the alarm and
trip circuit as well as to annunciator provided on the control board.
5.9 SCHEME OF PROTECTION FOR 25KV OVERHEAD EQUIPMENT
5.9.1 The sub-station equipment as well as the over head equipment is protected
against short circuit and over load by means of feeder circuit breakers .Norally the tracks on
one side of the sub-station are fed through one feeder circuit breakers in case defect on one
feeder,the other feeder circuit breaker is arranged to feed track on both side of the substation.To
protection scheme shall full-fill the following function
i) To detect all short circuit over the zone of overhead equipment fed by the feeder
circuit breaker.
ii) To operate with minimum delay in opening the circuit breakers.
iii) To refrain from operation at the maximum working current i.e discriminate between
the maximum load currents and short circuit current even though the magnitude of
the former is at time more than the latter especially when the fault are remote from
the sub-station
iv) To detect and isolate fault on the OHE caused by accidental coupling of two different
phase from adjacent sub-station
v) To provide single shot auto-reclosing of the feeder circuit breaker after a present
time interval adjustable between0.5secs.to 30 secs.
vi) To reclose the 25kv feeder circuit breaker through single shot automatic reclosing
scheme in the event of feeder circuit breakers tripping on fault through any of the
three relays viz.admitance(MHo)relay for wrong phase coupling and instantaneous
over current relay.
vii) To detect and isolate the flashover caused by pantograph on an overlap in front of
Traction Substation when panto moves from live to dead section over the insulated
over lap. This protection is provided by panto flasover Relay.
viii) To detect and isolate a high resistance OHE ground fault. This fault can not be
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