GE 750 User Manual

17-
38
750/760 Feeder Management Relay GE Power Management
17.7 PROTECTION SCHEMES 17 COMMISSIONING
17
Pickup with Two or Three Phases For Operation:
1. Inject
V
ab
= V
cb
> pickup into the bus voltage input. The PICKUP indicator should be on.
2. Lower
V
ab
until the PICKUP indicator goes out. This is the reset voltage, which should be the pickup value
minus 2% of VT.
3. Slowly raise
V
ab
until the PICKUP indicator comes on. This is the pickup voltage.
4. Repeat steps 1 through 3 except adjust
V
bc
.
c) FOR WYE and DELTA VTs
Test Connections per Figure 17–1: RELAY TEST WIRING – WYE CONNECTION or Figure 17–2: RELAY
TEST WIRING – DELTA CONNECTION on page 17–4. 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 1 TRIP Relay".
Timing:
1. Connect the “Stop Trigger."
2. Set the voltage source to the required test voltage, then turn off voltage.
3. Reset the timer. Turn the voltage on in the required number of phases, 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.”
17.7.26 NEUTRAL DISPLACEMENT (WYE VTs ONLY)
Test Connections per Figure 17–1: RELAY TEST WIRING – WYE CONNECTION on page 17–4.
Pickup Level:
1. Apply a three phase balanced nominal voltage to the relay.
2. Reduce
one phase voltage slowly until the Neutral Displacement element operates. Note this voltage.
3. Calculate the 3
V
o
(neutral voltage i.e. residual voltage) being supplied to the relay using the formula:
3
V
o
= V
a
+ V
b
+ V
c
.
4. Repeat steps 1 through 3 except adjust
V
bn
and V
cn
in turn.
Blocking From Logic Inputs:
1. Cause a pickup of the Neutral Displacement element.
2. Assert a logic input to provide a "Blk Ntr Displacement". 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. Preset the neutral (residual) voltage to be 150% of the pickup setting.
3. Inject the preset neutral (residual) voltage into the relay and note the delay time. Reset the timer.
4. Repeat step 3 four more times and obtain an average of the time intervals. Disconnect the stop trigger
when finished.

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English