is not tripped after any reclosure.
2.7.5.7
Transformer Differential and Lockout Relays
Differential relays, device 87T, shall be of the three-phase or the
single-phase high-speed [_____] [percentage] [_____] differential type
suitable for the protection of two-winding transformers, and shall be
provided with a harmonic-restraint feature. Lockout relay, device 86T,
shall be of the type which, when used in conjunction with the 87T relay,
trips and locks out the indicated circuit breakers.
2.7.5.8
Bus Differential and Lockout Relays
Bus differential relay, device 87B, shall be of the three-phase or
single-phase, high-speed impedance differential type suitable for
protection of buses. Lockout relay, device 86B, shall be of a type which,
when used in conjunction with the 87B relay, trips and locks out the
indicated circuit breaker.
2.7.6
Control and Instrument Switches
Control and instrument switches shall be of the rotary switchboard type
rated for alternating-current operation at 600 volts, or direct-current
operation at 250 volts for dc circuits, as applicable. Contacts shall be
rated for not less than a continuous current of 20 amperes, shall be of the
silver-to-silver type, and shall have positive means for maintaining
contact. Each switch shall be provided with a black operating handle, and
an escutcheon clearly marked to show each operating position. Switch
identifications and handle positions shall be engraved on escutcheons or
may be provided on separate nameplates. Escutcheon engravings shall be
white on a black background or black on a white background. Instrument
switches for potential phase selection shall be provided with an oval
handle. Ammeter switches for phase selection shall have round, notched, or
knurled handles and equipped with short-circuiting type of contacts to
prevent open-circuiting of current transformer secondary circuits in any
position of the ammeter switches. Switches provided for circuit breaker
control and local-remote selector switches shall have a pistol-grip handle
and a mechanical target to indicate the last operating position of the
switch. Red and green circuit breaker position indication LED lights shall
be installed immediately above each circuit breaker switch. Local-remote
selector switches shall be provided only when shown or specified. Position
indication lights shall be installed immediately above selector switches,
with blue LED lights indicating remote control and amber LED lights
indicating local control.
2.7.7
Electrical indicating instrument relays shall comply with ANSI C12.1, ANSI
C12.4, ANSI C12.10, and ANSI C39.1. [Electrical indicating instruments
shall be of the semiflush, back-connected, dustproof, direct-reading,
switchboard type, approximately 108.0 mm square 4-1/4 inches square, with
white dials, black markings, black pointers, and scale arcs of
approximately 250 degrees. Cases shall have a black finish and shadowproof
viewing covers. The accuracy of each instrument shall be within 1 percent
of full scale. Moving elements shall be provided with zero adjustments
readily accessible from instrument fronts without disassembly. Each
instrument shall be accurately calibrated for use with the associated
instrument transformers, and shall have the indicated scale or a scale
suitable for the application, where a specific scale is not indicated.
SECTION 16311A
Page 46
Previous Page
