MIL-HDBK-1191
period of 15 minutes before shutdown, after which the controls will
automatically reset for a new cycle. A manual start switch will override the
automatic start of engine generator sets so they can be manually cranked,
synchronized, and connected to the emergency bus, if automatic controls fail.
Additional manual controls will be provided as indicated elsewhere in this
section.
AUTOMATIC TRANSFER SWITCHES (ATS). All ATSs will be double-throw
10.3.11
with draw-out construction. Contacts will have viewing ports for ease of
contact inspection. ATSs shall have been UL tested with the main up-stream
breaker to assure coordinated withstand compatibility between the ATS and the
interruption time of the breakers. Circuit breaker type transfer switches are
not acceptable . Each ATS will have indicator lights to identify Normal Power
(green in color) and Emergency Power (red in color). All ATSs will be equipped
with a load break by-pass isolation switch (The by-pass isolation switch can
be initiated with not more than two movements of the hand to either position
regardless of the position or condition of the ATS.) to maintain normal or
emergency power while the ATS is being repaired or maintained. Load bypass to
the ATS's connected source will be achieved with either no load interruption,
or a load interruption of not more than 10 (CYCLES) hertz. ATSs feeding high
efficiency motors rated 25 horsepower or larger will be provided with an in-
phase monitor to prevent an out-of-phase transfer. The in-phase transfer will
be achieved without control of the frequency of either power source to prevent
excessive motor in-rush current. Use of closed-transition switching for
facilitating essential system testing requires special justification and
approval. The by-pass isolation switch for the ATSs serving nonessential
equipment can be optional.
Laboratory
10.3.12
ATS AND BYPASS/ISOLATION SWITCH (BP/IS),TESTING.
testing will be conducted on the ATS and BP/IS to be supplied for this
facility, or shall have been completed on a previous, randomly selected
standard production ATS and BP/IS unit having the same model and capacity as
the ATS and BP/IS specified. The overload, endurance, and temperature tests
shall be conducted in the following specified sequence:
a.
General.
b.
Normal Operation.
c.
Overvoltage.
d.
Undervoltage.
e.
Overload.
f.
Endurance.
g.
Temperature Rise.
h.
Dielectric Voltage - Withstand.
i.
Contact Opening.
j.
Dielectric Voltage-Withstand (Repeated).
k.
Withstand.
l.
Instrumentation and Calibration of High Capacity Circuits.
m.
Closing.
n.
Dielectric Voltage - Withstand (Repeated).
o.
Strength of Insulating Base and Support.
No deviation from the test sequence will be granted. Approval will not be
granted to deviate from the overload, endurance and temperature test sequence.
GROUND FAULT PROTECTION EQUIPMENT. The essential electrical
10.3.13
system will not be provided with ground fault protection devices. The
generator circuit breaker and essential electrical main distribution board
circuit breaker will be provided with ground fault detection features, when
required, to indicate a ground fault and sound an audible alarm but not trip
the breaker (See paragraph 10.3.1, "ALTERNATE ELECTRICAL SOURCE").
REMOTE ALARM ANNUNCIATOR. A remote alarm annunciator, storage
10.3.14
battery powered, will be provided in a location readily observed by operating
personnel at a regular work station. The annunciator will indicate alarm
10-9
Previous Page
