Westinghouse KC-4, Инструкция по установке, эксплуатации и обслуживанию

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With the contact closed, the electrical connec­
tion is made through the stationary contact
housing clamp, to the moving contact, through
the spiral spring out to the spring adj uster clamp.
TRANSFOR M E R
The transformer is a saturating type consisting
of a tapped primary winding and a secondary
winding. A varistor is connected across the
secondary winding to reduce the voltage peaks
applied to the induction cylinder unit and phase
shifting capacitor.
I NDICAT I N G C ONTACTOR SWITCH U N IT
(ICS)
The indicating contactor switch is a small de
operated clapper type device. A magnetic arma­
ture, to which leaf-spring m ounted contacts are
attached, is attracted to the magnetic core upon
energization of the switch. When the switch closes,
the moving contacts bridge two stationary con­
tacts, completing the trip circuit. Also during this
operation two fingers on the armature deflect a
spring located on the front of the switch, which
allows the operation indicator target to drop. The
target is reset from the outside of the case by a
push rod located at the bottom of the cover.
The front spring, in addition to holding the
target, provides restraint for the armature and
thus controls the pickup value of the switch.
OPERATI ON
I N STANTAN EOUS OVERC U R R ENT U N IT
Operation of the instantaneous overcurrent
unit occurs when the primary current of the trans­
former exceeds a value as marked on the tap plate.
Upon application of current to the transformer, a
voltage is induced in the secondary winding. This
voltage is impressed upon the parallel connected
pairs of cylinder unit coils. The capacitor con­
nected in series with one pair of coils shifts the
current flowing in these coils in reference to the
current flowing in the other pair of coils. As a
result, the air gap fluxes o f the cylinder unit are
out of phase and a contact closing torque is
produced.
The primary of the transformer is tapped and
brought out to a tap connector block for ease in
changing the pickup current of the relay. The use
of a tapped transformer provides approximately
the same energy level at a given m ultiple of pickup
current for any tap setting, resulting in one time
curve throughout the range of the relay.
B R EAKER FAI LURE S C H E M E S U S I N G T H E
KC-4 R ELAY
The following explanations frequently refer to
the type TD-5 timing refay, which is usually used
in conjunction with the KC-4 relay for breaker
failure protection. For detailed data on the TD-5,
refer to instruction leaflet 4 1 -579. 1 .
SINGLE B U S/SI NGLE B REAKER
ARRANGE M ENT
In a properly functioning breaker, current
flow should cease shortly after the trip circuit is
energized. The time interval between trip-circuit
energization and current flow cessation is the
breaker-interrupting time. If interruption doesn't
occur within the s pecified interrupting time, the
breaker is assumed to have failed and the breaker­
failure relaying should initiate tripping of adjacent
and/ or remote breakers to isolate the protected
breaker. For the single bus-single breaker config­
uration, all the breakers on the bus m ust be tripped
to isolate any one of them which fails. This is
readily accomplished by having the breaker-failure
protection circuits energize the bus-differential
lockout auxiliary 86B.
Figure 2 shows the simplest breaker-failure
scheme using the KC-4 relay. Primary and backup
line relays connected to separate current trans­
formers and separately-fused de supplies so that a
failure in either circuit will not disable all of the
protection. When primary protection operates, it
energizes auxiliary relay 62X and the breaker trip
coil simultaneously. Similarly, backup relays
energize both tripping auxiliary 94T and auxiliary
62Y simultaneously. 62X and 62Y are k nown as
breaker-failure initiate (BFI) auxiliaries. The
closure of contacts 62X and 62Y provide a signal
in the breaker failure scheme that breaker tripping
3
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