MIL-HDBK-1003/11
is included to sense normal source failure, initiate starting of the engine
generator, and transfer the load to the generator. When the normal source
is restored, the switch will automatically transfer the load back to the
normal source and shutdown the engine after a predetermined time.
8.2.3.2 Multiple Ground Points. Emergency or standby power supplies in
conjunction with the normal incoming utility service for low-voltage systems
can introduce objectional stray currents because of the multiplicity of
neutral grounds. A properly designed ground system is necessary to
eliminate stray neutral current paths and undesirable ground-fault current
sensing path. Grounding arrangements for emergency and standby power
systems are discussed in the Institute of Electrical and Electronics
Engineers (IEEE) 446, Recommended Practice for Emergency and Standby Power
Systems for Industrial and Commercial Applications.
8.3 Operating Control Requirements. Requirements depend upon the size,
complexity, and voltage level of the plant. Requirement covered herein
apply to medium-voltage, multiple-unit plants and should be adjusted as
appropriate for low-voltage plants which are often single-unit plants.
Devices should be arranged on control switchboards or switchgear in a simple
and distinctive number of circuit breakers to be operated provides a complex
electric configuration, consider providing a mimic bus. Organize devices by
unit control, synchronizing control, and system monitoring.
8.3.1 Unit Control.
Minimum unit control should provide the following
devices:
a)
1)
Control switch.
2)
Ammeter and transfer switch.
b) Power sources such as generators or commercial input require
synchronizing switches.
c)
Generators.
1)
Voltage regulator adjusting rheostat.
2)
Voltage regulator manual-off-automatic switch.
3)
Governor switch.
4)
5)
Varmeter
6)
Watthour (Wh) demand meter.
7)
Elapsed operating time meter.
8.3.2 Synchronizing Control. The synchronizing control is energized
through the synchronizing control switch at the selected source and consists
of the following devices:
a)
Synchroscope.
b)
Bus frequency meter.
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