Specifications

NAIROBI OPERATIONAL HUB
UNOPS Building, UN Lane, Off UN Avenue Tel: [phone]
P.O Box 783,Village Market, 00621 E-mail: [e-mail]
Nairobi, Kenya Website: www.unops.org
UNOPS is ISO 9001 certified
e. The maximum link resistance from toroid to relay link must not
exceed 3 ohms.
Current operated earth leakage relays shall be used either in
conjunction with circuit breakers for tripping the breakers or for
giving alarm signal only by an indicator lamp and alarm bell in
cases of earth leakage.
2.10 EARTH BUS
The copper earth bus shall be minimum 50% of the phase conductor size
extending throughout the length of the switch board and fixed to the steel
members of the switch board. The earth bus shall be extended at the ends for
connection to the earth electrodes and shall have provision for terminating earth
continuity conductors.
2.11 MAIN AND SUB-MAIN DISTRIBUTION BOARDS
A. The main and sub-main distribution boards shall be totally enclosed, dust
protected and factory fabricated suitable for operation on 415/240 V, 3
phase, 4 wire, 50 Hz supply.
B. Main and sub-main distribution boards shall comprise main incoming
isolator, busbars, moulded case circuit breakers, earth leakage relays, earth
bus etc. with ratings and arrangement as shown on the Drawings and all
housed in a sheet steel panel fully rust-proofed and electro static powder
coated paint; equipped with a hinder door with approved locking device.
C. The main isolator shall be a triple pole and neutral moulded case circuit
breaker without tripping element.
D. The busbars shall be high conductivity copper bars to B.S. 159 with
ratings as indicated on the Drawings for the three phases and neutral. The
busbars shall be arranged and marked to the approval of the Engineer.
E. The moulded case circuit breakers and earth leakage relays shall be as
specified in paragraph 2.08 and 2.09 above.
F. The rated service breaking capacity (ICS) of MCCBs shall be 50 KA for
MLTP, 28KA for MDBE, 22 KA for MSBs and MCCs, 14 KA for SMSB
and MCC fed from MSB unless indicated otherwise on the Drawings.