GE 750 User Manual

17-
24
750/760 Feeder Management Relay GE Power Management
17.7 PROTECTION SCHEMES 17 COMMISSIONING
17
17.7.5 PHASE INSTANTANEOUS OVERCURRENT 1
The procedure to test this element is identical to Section 17.7.3: PHASE TIME OVERCURRENT 1 on page
17–21, with the following exceptions. Pickup, Indication and Operation are subject to the test 'phases required
for operation' and not subject to the tests 'linear reset timing' and 'voltage restrained phase time overcurrent'.
Pickup with Two Phases For Operation:
1. Inject current into phase B at 150% of pickup.
2. Inject current at a level below the pickup level into phase A.
3. Slowly increase the phase A current until the PICKUP indicator comes on. Note the pickup value.
4. Slowly reduce the phase A current until the PICKUP indicator goes out. Note the dropout level, which
should be 2% of CT less than pickup when pickup
≤
CT or 97 to 98% of pickup when pickup > CT.
5. Repeat steps 1 through 4 for each other pair of phases; B and C, and C and A.
Pickup with Three Phases For Operation:
1. Inject current into phase B and C at 150% of pickup.
2. Inject current at a level below the pickup level into phase A.
3. Slowly increase the phase A current until the PICKUP indicator comes on. Note the pickup value.
4. Slowly reduce the phase A current until the PICKUP indicator goes out. Note the dropout level, which
should be 2% of CT less than pickup when pickup
≤
CT or 97 to 98% of pickup when pickup > CT.
5. Repeat steps 1 through 4 for current at 150% in phases C and A and adjusted in B.
6. Repeat steps 1 through 4 for current at 150% in phases B and A and adjusted in C.
Blocking From Logic Inputs:
1. Inject current into the required number of phases to cause a pickup.
2. Assert a logic input to provide a "Block Phase Inst 1". The PICKUP indicator should immediately go out.
3. Repeat 1 and 2 for logic inputs "Block Phase O/C", "Block All O/C" and “Block 1 TRIP Relay” as required.
Timing:
1. Connect the Stop Trigger to the interval timer.
2. Preset the current source to a minimum of 110% of pickup current. Turn the current off, and reset the timer.
3. Inject the preset current into the required number of phases and note the delay time. Reset the timer.
4. Repeat step 3 four more times and obtain an average of the time intervals.
5. Reset the relay and disconnect the “Stop Trigger.”
17.7.6 PHASE INSTANTANEOUS OVERCURRENT 2
The procedure to test this element is identical to that outlined in Section 17.7.5: PHASE INSTANTANEOUS
OVERCURRENT 1 on page 17–24, with the following exception.
Blocking From Logic Inputs:
1. Inject current into the required number of phases to cause a pickup.
2. Assert a logic input to provide a "Block Phase Inst 2". The PICKUP indicator should immediately go out.
3. Repeat 1 and 2 for logic inputs "Block Phase O/C", "Block All O/C" and “Block 1 TRIP Relay” as required.

GE 750 Specifications

General

Brand	GE
Model	750
Category	Relays
Language	English