Sensitive Ground Directional Overcurrent - GE 750 Instruction Manual

17.7 PROTECTION SCHEMES 17 COMMISSIONING

17.7.18 SENSITIVE GROUND DIRECTIONAL OVERCURRENT

The procedure to test this element is identical to that outlined for Section 17.7.12: NEUTRAL DIRECTIONAL
OVERCURRENT on page 17–28, except the operating current is the sensitive ground current.
17.7.19 NEGATIVE SEQUENCE TIME OVERCURRENT
The procedure to test this element is identical to that outlined for Section 17.7.3: PHASE TIME OVERCUR-
RENT 1 on page 17–21, with the following exceptions.
Current is injected into any one phase of the phase input terminals and the negative sequence current magni-
tude is 1/3 of the injected current. The element is not subject to the "phases required for operation" or "voltage
restrained time overcurrent" tests.
Blocking From Logic Inputs
1. Inject current to cause a pickup.
2. Assert a logic input to provide a "Block Neg Seq Time". The PICKUP indicator should immediately go out.
3. Repeat steps 1 and 2 for logic input "Block All O/C" and "Block 1 TRIP Relay" as required.
17.7.20 NEGATIVE SEQUENCE INSTANTANEOUS OVERCURRENT
The procedure to test this element is identical to that outlined for Section 17.7.5: PHASE INSTANTANEOUS
OVERCURRENT 1 on page 17–24, with the following exceptions.
Current is injected into any one phase of the phase input terminals and the negative sequence current magni-
tude is 1/3 of the injected current. The element is not subject to the "phases required for operation" test and not
subject to the tests "linear reset timing" and "voltage restrained time overcurrent".
Blocking From Logic Inputs
1. Inject current to cause a pickup.
2. Assert a logic input to provide a "Block Neg Seq Inst". The PICKUP indicator should immediately go out.
3. Repeat steps 1 and 2 for logic input "Block All O/C" and "Block 1 TRIP Relay" as required.
17
17.7.21 NEGATIVE SEQUENCE DIRECTIONAL OVERCURRENT
The procedure to test this element is identical to that outlined for Section 17.7.7: PHASE DIRECTIONAL
OVERCURRENT on page 17–25, except the injected current must be a negative sequence current.
17- 750/760 Feeder Management Relay GE Power Management
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