Modified Part 2 Tender Document - Naya Raipur

NRDA F-1- Schedule-D- Section III- Technical Specification of Works
Construction of Forest and Water Resources department buildings, North Block at Naya Raipur
NRDA
HT Panel shall have suitable compartments for prescribed circuit breaker and its withdrawable
truck. Suitable rails shall be provided for inside the housing for the wheels of the truck. The circuit
breaker shall be mounted such that it is easily accessible from the front of the panel. All
instruments and meters shall be mounted flush on the front of the panels above the circuit breaker.
Potential transformer, shall be mounted on the rear of the HT Panel.
7. Interlocking and safety arrangements
HT panel shall be provided with the following interlocking and safety arrangement.
i) The breaker cannot be plugged in unless it is `off'.
ii) The breaker cannot be drawn out when it is `on'.
iii) The access to bus bar is prevented by automatic shutters when breaker is removed.
iv) The circuit breaker cannot be put into service without completing the protective electrical and
earth circuits.
v) A safety catch to ensure that the movement of the breaker as it is withdrawn, is checked before it
is completely out of the panel shall be provided.
8. Shutter Gear
Suitable shutter gear shall be provided for shrouding of bus bar and feeder orifices. These shutters
shall be automatic in operation. Suitable hinged shutters with padlocking arrangement shall also be
provided in addition to the automatic shutters.
9. Protection & Instrumentation, metering & indication
CURRENT TRANSFORMER
a) General Requirements
Accommodation shall be provided in the circuit breaker panel to mount 2 sets of CT's one reserved
for protection and the other for metering/instrumentation purposes. Access to the CT's for cleaning
testing or changing shall be from the front back or top of the panel.
b) Rating
Dual ratio CTs suitable burden (but not less than 15 VA burden) shall be preferred with 5 amps
secondaries. The ratio shall normally be one of the following specified :
. 50/25/5
The CTs shall conform to relevant Indian Standards. The design and construction shall be robust to
withstand thermal and dynamic stresses during short circuits. Secondary terminals of CTs shall be
brought out suitably to a terminal block which shall be easily accessible for testing and terminal
connections. The protection CTs shall be of accuracy class 15 P 10 of IS : 2705 - Part III-1992.
The metering CTs shall conform to the metering ratio and accuracy class 0.5 of IS 2705.
10. Voltage Transformer
Page 18 of 174