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
B) Main Contacts Open ‘Off’,
C) Springs Charged,
D) Springs Discharged
E) Service Position,
F) Test Position, And
G) Isolated Position For Drawout Mechanism.
D. Any attempt to withdraw or insert the breaker when it is ‘ON’ shall trip
the breaker automatically. An interlocking shall be provided to prevent
insertion of a circuit breaker having a rating higher than the current rating
of the ACB cradle.
E. Insulated safety shutters shall screen all live parts in the ACB cradle when
the breaker is in the isolated or racked out position.
F. The moving contacts comprising the main and arcing contacts shall have
visual wear indicator and be of the spring loaded type. The main contacts
and clusters shall be site replaceable. The electrical endurance shall not be
less than 4000 operations for rating up to 3200A and not less than 2000
operations for ratings above.
G. The circuit breakers shall have sufficient number of auxiliary contacts for
interlocking system as indicated and described on the drawings and for
interfacing with building automation system (BAS), with two spare sets of
normally open and normally closed contacts. It shall be possible to
connect all auxiliary wiring from the front face of the air circuit breakers
and this wiring shall be taken through a set of disconnecting contacts, so
that all auxiliary wirings are automatically disconnected in the isolated and
drawout positions.
H. The circuit breakers shall be equipped with MCR, overcurrent and earth
leakage protections by means of integral self-powered microprocessor
based solid state RMS sensing current relays. The long time overcurrent
protection shall have a setting range between 40 and 100 per cent of
sensor rating in steps of 2 per cent. The corresponding time delay shall be
adjustable from 15 to 480 seconds The short time overcurrent protection
shall have a setting range from 40 per cent to 15 times the sensor rating.
The corresponding time delay shall be adjustable from 15 seconds. The
sort times the sensor rating. The corresponding time delay be adjustable
from instantaneous to 400 milliseconds with the possibility select time
inverse characteristic for improved discrimination. Instantaneous