range of [_____] to [_____] amperes.[
Relays shall be Type [_____].]
e.
Directional ground overcurrent relays (device 67N): Provide
directionally controlled time overcurrent relays sensing ground
(residual) current. Relays shall be wired to trip the associated
circuit breaker upon a current exceeding the tap setting in the
direction indicated. Relays shall have a current and voltage polarized
directional unit and an inverse time characteristic overcurrent unit.
Relays shall be voltage polarized. Auxiliary potential transformers
shall be provided to obtain polarizing voltage. Overcurrent unit shall
have a tap range of [_____] to [_____] amperes.[ Relays shall be Type
[_____].]
f.
Lockout relays (device 86): Provide hand reset, electrically tripped,
high-speed auxiliary relays where indicated. Relays shall be tripped
by the indicated devices and shall be wired to trip the associated
circuit breaker and prohibit closing of the circuit breaker by local
and remote controls until the lockout relay has been reset by hand to
its normal position. Each relay shall be provided with the number of
contacts required to perform the indicated function and, in addition,
shall have a minimum of two spare normally closed contacts and two
spare normally open contacts.
g.
Bus differential relays (device 87B): Provide a set of three
high-speed, high-impedance, single-phase bus differential relays, wired
to trip the circuit breakers connected to the protected bus upon
occurrence of a fault within the zone of protection. Relays shall not
trip the circuit breakers on through current to a fault outside the
zone of protection. Current signals shall be obtained from dedicated
current transformers. Bus differential relay shall include a
voltage-operated unit which shall operate in three to six cycles for
low-magnitude faults and a current-operated unit which shall operate in
one to three cycles on moderate to severe faults. Relay shall include
a thyrite voltage-limiting unit. Voltage-operated unit shall have an
adjustment range of 75 to 500 V. Current-operated unit shall have an
adjustment range of 2 to 50 amperes.
[h.
Trip blocking test switches: Trip blocking test switches shall be
provided to block tripping of 34.5-kV circuit breakers from the bus
differential lockout relay. Trip blocking test switches shall be
back-connected knife switches in a semiflush panel-mounted insulating
case with removable clear glass or acrylic cover. Knife switches shall
be rated for at least 125 Vdc and 30 amperes. Knife switches shall
have an insulated operating knob.]
[i.
Transformer differential relays (device 87T): Provide a set of three
high-speed, percentage differential relays for protection of
three-phase, delta-wye, two-winding transformer. Relays shall sense
phase currents from the transformer primary current transformers and
transformer secondary breaker current transformers. Relays shall trip
the primary circuit breakers and the transformer secondary breakers.
Relays shall have a sensitive differential unit to detect faults within
the protected zone. Relays shall have a harmonic restraint unit to
prevent tripping on transformer inrush current and two restraint
transformers to prevent tripping on through-current to a fault outside
the zone. Relays shall have a sensitivity of 0.35 times the tap value.
Relays shall have ratio taps in the range of 2.9 to 8.7 amperes.
Relays shall be Type [_____].]
SECTION 16361N
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