2.5.8
Instrument Transformers
2.5.8.1
Voltage Transformers
Five 480-120 volt, 200 volt-ampere capacity, voltage transformers shall be
provided for each main 480-volt bus section. Two of the transformers shall
be used for metering and 3 of the transformers shall be used with the
ground detection equipment. Voltage transformers shall conform to IEEE
C57.13 and shall have an ANSI accuracy classification of 0.3W, 0.3X, and
1.2Y or better. The full-wave impulse level shall be not less than 10 kV.
Each voltage transformer shall be protected with removable primary and
secondary fuses. Fuses shall be installed in each ungrounded lead and
located adjacent to the transformers in an easily accessible place.
2.5.8.2
Current Transformers
Dry type current transformers as shown shall be furnished, installed and
wired to the specified terminal blocks. These current transformers shall
conform to IEEE C57.13, and shall have the ratios indicated. The current
transformers shall be rated not less than 600 volts AC, 10 kV BIL, and the
ANSI accuracy classification shall be in accordance with [IEEE C37.20.1][
IEEE C37.20.2][IEEE C37.20.3], or better. If cable connections to the
transformer primary are required, terminals of an approved solderless type
and proper size shall be furnished. If transformers are connected to
buses, proper connections shall be furnished, complete with bolts, nuts,
washers and other accessories.
2.5.9
Ground Detection Equipment
Ground detection equipment shall be furnished for each bus section of the
switchgear, to be used for indication and annunciation of grounds of the
480-volt system. The equipment shall consist of 3 instrument voltage
transformers complete with primary and secondary fuses, connected
wye-delta, with neutral of primary wye grounded and with the coil of a
voltage ground detector relay connected in the broken delta corner of the
secondary windings of the 3 voltage transformers in accordance with [IEEE
C37.20.1][IEEE C37.20.2][IEEE C37.20.3]. Two ground detector relays shall
be provided, one for each bus section of the switchgear.
2.5.10
Relays
2.5.10.1
General
a. Relays shall conform to the applicable requirements of IEEE C37.90.
The relays shall be back-connected, semi-flush-mounted, switchboard
type with black, rectangular, dust-tight cases, removable covers with
windows, and means of sealing against tampering. Relays, except
auxiliary relays, shall be drawout type with built-in test facilities
arranged so that the relays can be tested in position or withdrawn from
the fronts of the cases without opening current transformer secondary
circuits, disturbing external circuits, or requiring disconnection of
leads from the relay terminals. The test devices shall permit testing
with energy from either the instrument transformers or an external
b. Protective relays shall be provided with all required auxiliaries,
including auxiliary instrument transformers and reactors, to adjust
currents, potentials and phase angles for proper operation. External
relay auxiliaries shall be mounted in compact assemblies back of the
SECTION 16404A
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