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,
Coordinated Power System Protection) to specify the
breaker ratings, breaker trip unit features and
settings, relay protection scheme, and relay
settings for coordination for each genset installed.
The configuration should always include a
disconnecting means for isolation of the generator
for maintenance purposes. If the scope of
protection is small the designer may elect to
incorporate the appropriate UFGS-16475A COORDINATED
POWER SYSTEM PROTECTION, paragraphs in this section.
Show panelboard, switchboard, and switchgear
ratings on the contract drawings for each genset.
Rating information should include voltage, phase,
bus continuous capacity (amperes), and bus withstand
capacity (amperes) (see NEMA PB 1, NEMA PB 2, and
NEMA SG 6 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 for
separately derived sets which 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.
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Devices necessary for electrical protection and isolation of each
engine-generator set and its ancillary equipment 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
withstand, and interrupting current ratings to match the generator
capacity. The generator circuit breaker shall be [manually operated]
[electrically operated] [operated as indicated]. A set of surge
capacitors, to be mounted at the generator terminals shall be provided.
Monitoring and control devices shall be as specified in paragraph GENERATOR
PANEL.
2.16.1
Switchboards
Switchboards shall be free-standing, metal-enclosed, general purpose,
3-phase, 4-wire, [600] [_____] volt rated, with neutral bus and continuous
ground bus, conforming to NEMA PB 2 and UL 891. Neutral bus and ground bus
capacity shall be [as shown] [full capacity]. Panelboards shall conform to
NEMA PB 1. Enclosure designs, construction, materials and coatings shall
be [as indicated] [suitable for the application and environment]. Bus
continuous current rating shall be [at least equal to the generator rating
and correspond to the UL listed current ratings specified for panelboards
and switchboards] [as indicated]. Current withstand (short circuit rating)
SECTION 16263A
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