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
The bus bars shall be provided with colored PVC sleevings at regular
intervals for phase identification. Painted bus bars may be acceptable in
special cases when panels are manufactured/assembled in Jordan.
2.03 AIR CIRCUIT BREAKERS
A. The air circuit breakers shall be of the air break trip free draw out type with
the main contacts encased in a reinforced polyester casing and offer double
insulation from the operators on the breaker front face. The air circuit
breaker shall be fully tropicalized (T2) as defined in IEC 68.2.30 and shall
have salt spray resistance as per IEC 68.2.11. The ACB shall comply with
IEC 947.2 utilization category B with Ics=Icu=Icw and shall accept reverse
feeding without reduction of performance. The ACB shall comply with the
isolating function requirements of IEC 947.2 section 7.1.2 and shall have
minimum 500 V 50Hz operational voltage, 1000 V 50 Hz rated insulation
voltage and 8kV withstand surge voltage (Vimp). The 3-pole and 4-pole
versions shall have ratings as shown in the drawings. In the 4 pole version
the neutral pole shall have the same current rating as the other poles from
800 to 4000A . The breaking capacities shall not be less than 50 kA
symmetrical for 1 sec. at 415 volt. Evidence of the service breaking capacity
(Ics) shall be produced by test certificates from one of the internationally
recognized testing Laboratories. (ASTA, CESI, ESEF/ASEFA, KEMA,
PEHLA or SATS).
B. Unless otherwise mentioned the ACB shall be of the O-C-O stored energy
spring type with a closing time less than or equal to 80 millisecond.
Electrically operated circuit breakers shall have the spring charging motor
connected so that the springs remain charged always with the motor
disconnected after charging. The spring charging time shall not exceed 4
seconds. A standby manual operating handle for spring charging shall be
provided for operating the circuit breaker in case of power or motor failure.
Antipumping shall be provided by integral devices to prevent reclosing after
a close-open operation if the closing impulse is maintained after the breaker
has opened. External relays are not acceptable
C. The circuit breaker shall have three positions of the drawout mechanism,
namely service position where all main and auxiliary contacts are made,
test position where main contacts are open but auxiliary contacts are
closed and isolated position where all contacts are open. Mechanical
indication on the front of the ACB shall be provided to indicate
A) Main Contacts Closed ‘On’,