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3.3 INDICATORS
3 SETUP AND OPERATION
3.3 INDICATORS
3.3.1 STATUS INDICATORS [9]
a) RELAY IN SERVICE
Immediately after applying control power, the 735/737 relay performs a series of self checks. Assuming all checks are suc-
cessful, the RELAY IN SERVICE indicator comes on and protection is operational. Continuous checks are also made by
the relay of its internal circuitry. If an internal failure is detected at any time, the RELAY IN SERVICE light goes out. The
SERVICE REQUIRED indicator and the SERVICE output relays are activated to warn that protection is not functioning cor-
rectly. This is a serious condition that requires immediate attention since the relay may not respond correctly to a fault.
Arrangements should be made to check or replace the relay. During simulation mode, this LED will be flashing.
b) SERVICE REQUIRED
If self checks by the internal microprocessor detect a fault with the relay, this indicator goes on and the SERVICE output
relay is activated to warn that protection is not functioning correctly. Failsafe operation of the SERVICE output relay by hav-
3
ing the coil continuously energized under normal conditions, ensures that a SERVICE output will be obtained on loss of
control power or when the relay is drawn out, even though the SERVICE REQUIRED indicator would be off under those
conditions. This is a serious condition that requires immediate attention since the relay may not respond correctly to a fault.
Arrangements should be made to check or replace the relay.
c) PHASE PICKUP
When the current in any phase exceeds the PHASE PICKUP control setting, this indicator flashes. If the condition persists,
the 735/737 will time out and trip with the TRIP 51-A/B/C indicator on.
d) GROUND PICKUP
Flashes when ground (neutral) current from the residual phase CT or separate core balance CT input (depending on
ground sensing connection) exceeds the GROUND PICKUP control setting. If the ground overcurrent persists, the 735/737
will time out and trip with the TRIP 51-N indicator on.
3.3.2 TRIP INDICATORS [10]
Fault indicators are provided to determine the cause of trip. Each indicator is latched and remains set after a trip until
cleared with the CLEAR key while control power is applied. When a trip occurs, the TRIP relay contacts are closed until the
three-phase and neutral currents are all zero. The trip output relays seal in for a further 100 ms then open. After the trip
relay opens, the trip LED will remain on steady until reset by pressing the CLEAR key at which time all the trip indicators go
off. For example, if indicator INSTANTANEOUS-N is on, the last trip was caused by a ground (neutral) instantaneous trip.
Indicators are set for all phases or ground that exceeded the time overcurrent pickup or instantaneous setting at time of trip.
Thus if indicators INSTANTANEOUS A and C are both on, a phase A to phase C fault occurred. If the breaker is closed
after a trip without pressing the CLEAR key, the cause of trip indicator will remain on steady. However, at the next trip, the
previous cause of trip indicator will be cleared so that only the most recent cause of trip indicator is on.
Hold the CLEAR key down for 2 seconds and the trip indicators will display in sequence the last five causes of trips, starting
with the most recent. This trip record is useful for analyzing a recurring fault.
a) PHASE TIME O/C – A, B, C TRIP INDICATORS
If the PHASE PICKUP level is exceeded long enough by any phase current to cause a trip according to the selected phase
time overcurrent curve, a trip occurs and the corresponding A, B, or C indicator will be set to indicate a phase time overcur-
rent trip.
b) PHASE INSTANTANEOUS A, B, C TRIP INDICATORS
When the current in any phase exceeds the PHASE INSTANTANEOUS setting, the relay will trip and the corresponding A,
B, or C indicator will be set to indicate a phase instantaneous trip.
c) GROUND TIME O/C TRIP
If the ground (neutral) current exceeds the GROUND PICKUP level long enough to cause a trip according to the selected
ground fault time overcurrent curve this indicator will be set to indicate a ground overcurrent trip.
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735/737 Feeder Protection Relay
GE Power Management
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