shall have a maximum droop of 2% of rated voltage over a load range from 0
to 100% of rated output capacity and automatically maintain the generator
output voltage within the specified operational bandwidth.
2.15
GENERATOR PROTECTION
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NOTE: Generator protection shall be based on the
application and size of the generator and should
comply with the recommendations of IEEE Std 242 and
IEEE Std 446 for both generator breaker features and
protection schemes. See AFMAN 32-1077 for
recommended protection schemes for Air Force
projects. The designer must perform a power system
coordination study (reference TM 5-811-14) to
specify the breaker ratings, breaker trip unit
features and settings, relay protection scheme, and
relay settings for coordination for each generator
set installed. The configuration should always
include a disconnecting means for taking clearance
on the generator for maintenance purposes. If the
scope of protection is small the designer may elect
to delete the paragraphs in this section and
reference UFGS-16475A COORDINATED POWER SYSTEM
PROTECTION. Show panelboard ratings on the contract
drawings for each generator set. Rating information
should include voltage, phase, bus continuous
capacity (amperes), bus withstand capacity (amperes)
(see NEMA PB 1 for necessary rating information).
Show breaker frame, trip, and interrupting ratings
on the contract drawings.
Surge capacitors and surge arresters should be
provided when the sets are to be connected to
exposed overhead lines directly or through
transformers, even though connection may be only for
transfer of load without service interruption.
Surge arrester protection is not required where sets
serve single buildings isolated from overhead lines
by automatic or manual transfer switches where
provision has been made to prevent simultaneous
connection to both sources. The designer will
specify the surge arrester rating.
Fuse and circuit breaker ratings should be shown on
the contract drawings. Show voltage, phase,
continuous current (ampere), short circuit
withstand, interrupting, neutral size, etc.
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Short circuit and overload protection for the generator shall be provided.
The generator circuit breaker (IEEE Device 52) ratings shall be consistent
with the generator rated voltage and frequency, with continuous, short
circuit and interrupting current ratings to match the generator capacity.
The manufacturer shall determine the short circuit current interrupting
rating of the breaker. The breaker shall be engine generator base mounted
by the engine-generator set manufacturer. Molded case breakers shall be
provided with shunt trip. Surge protection shall be provided for each
phase of the generator, to be mounted at the generator terminals.
SECTION 16264A
Page 44
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