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
overcurrent protection shall be adjustable from 2 times the current up to
the circuit breaker electrodynamical withstand. The earth protection shall
have current settings from 10 per cent of the rated current 1200 A in steps
of 10 per cent. The time delay setting shall be variable 100 millisecond to
400 millisec in steps of 100 millisec.
J. The RMS value of the phase currents and interrupted current values shall be
displayed on the built-in digital ammeter and the LED’s shall indicate the
type of fault on the front face of the trip unit. An indicator shall give
indication of the main contact wear according to the number of operations
and the values of the switched currents. A bar graph shall display the load
indication of each phase and the highest value of phase currents shall be
stored and displayed on demand. Trip unit malfunction or internal
overheating shall be indicated by a self monitoring alarm.(Some features
may differ from one manufacturer to another)
K. The air circuit breaker used on bus-section shall be identical to Air Circuit
Breaker specified but with only the Making Current Release (MCR)
protections and instruments specified but with the following indications :
1. Circuit breaker closed.
2. Circuit breaker open.
3. Circuit breaker tripped.
L. The main low tension panels shall be provided with cable boxes to suit the
incoming cables from the transformer which are supplied and installed by
the concerned local authorities.
2.04 CURRENT TRANSFORMERS
Current transformers shall be of Class C accuracy for indication and Class CM
accuracy for metering purpose. The secondary windings shall be rated at 5A and
the rated output shall be suitable for the burden.
2.05 INSTRUMENTS
A. The measuring instruments shall include ammeter voltmeters, maximum
demand indicators and selector switches as indicated on the Drawings.
B. The instruments shall have anti-glare glass fronts, anti-parallax scales and
white faces with black numerals and markings. The instrument cases shall