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
characteristic. Tabulate recommended device tap, time dial, pick-up,
instantaneous, and time delay settings.
F. Include on the curve sheets power company relay and fuse characteristics,
medium voltage equipment relay and fuse characteristics, low voltage equipment
circuit breaker trip device and fuse characteristics, pertinent transformer
characteristics, pertinent motor and generator characteristics, and characteristics
of other system load protective devices. Include tolerance and damage bands in
plotted fuse characteristics.
G. Show transformer full load and 150, 400, or 600 percent currents, transformer
magnetizing inrush, ANSI transformer withstand parameters, magnetic in rush
current point and significant symmetrical and asymmetrical fault currents.
Terminate device characteristic curves at a point reflecting the maximum
symmetrical or asymmetrical fault current to which the device is exposed.
H. Select each primary protective device required for a delta-star connected
transformer so that its characteristics or operating band is within the transformers
characteristics. Where the primary device characteristic is not within the
transformer characteristics, show a transformer damage curve. Separate
transformer primary protective device characteristics by a percent current margin
to provide proper coordination and protection in the event of secondary line-to-
line faults. Separate medium voltage relay characteristic curves from curves for
other devices by at least 0.4 second time margin.
I. In each brochure, include complete sets of individual protective device time-
current characteristics on transparencies.
J. The short circuit and protective device studies may be prepared with a network
analyzer, digital computer or by written computations, but must include complete
fault calculations as specified herein for each proposed and ultimate source
combination.
K. The plans and specifications indicate the general requirements for the electrical
equipment being provided under this contract. Changes and additions to
equipment characteristics may be suggested by the results of the short circuit and
protective device coordination studies. Submit any such proposed changes and
additions as a part of the study brochure material. Necessary field settings of
devices, and adjustments and minor medications to equipment to accomplish
conformance with the approved short circuit and protective device coordination