GE 750, Instruction Manual

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GE Power Management 750/760 Feeder Management Relay 17-
33
17 COMMISSIONING 17.7 PROTECTION SCHEMES
17
17.7.22 NEGATIVE SEQUENCE VOLTAGE
Procedure To Check:
a) FOR WYE VTs
Test Connections per Figure 17–1: RELAY TEST WIRING – WYE CONNECTION on page 17–4.
A negative sequence voltage can be created by injecting a single phase voltage, or a set of three single-phase
voltages with a known negative sequence component. For single phase injection the negative sequence volt-
age magnitude is the injected voltage divided by 3.
Pickup:
1. Inject a negative sequence voltage = 0 into the bus voltage input of the relay. The PICKUP indicator should
be off.
2. Slowly raise the voltage until the PICKUP indicator comes on. This is the pickup level.
3. Lower the voltage until the PICKUP indicator goes out. This is the reset voltage, which should be 2% of VT
less than the pickup level.
b) FOR DELTA VTs
Test Connections per Figure 17–2: RELAY TEST WIRING – DELTA CONNECTION on page 17–4.
A negative sequence voltage can be created by injecting a single phase-phase voltage, or a set of two phase-
phase voltages with a known negative sequence component. For a single phase-phase injection the negative
sequence voltage magnitude is the injected voltage divided by
√
3.
Pickup
1. Inject a negative sequence voltage = 0 into the bus voltage input of the relay. The PICKUP indicator should
be off.
2. Slowly raise the voltage until the PICKUP indicator comes on. This is the pickup level.
3. Lower the voltage until the PICKUP indicator goes out. This is the reset voltage, which should be 2% of VT
less than the pickup level.
Indications and Operations are as outlined under Phase Time Overcurrent 1.
Blocking From Logic Inputs:
1. Inject voltage to cause a pickup.
2. Assert a logic input to provide a "Block Neg Seq Voltage". The PICKUP indicator should immediately go
out.
3. Repeat steps 1 and 2 for logic input “Block 1 TRIP Relay” as required.
Timing:
1. Connect the “Stop Trigger."
2. Set the voltage source to the required test voltage, then turn off the voltage.
3. Reset the timer. Turn the voltage on and measure the operating time. Repeat steps 2 and 3 four more
times and obtain an average of the time intervals.
4. Reset the relay and disconnect the “Stop Trigger.”