Ground Overcurrent - GE 750 Instruction Manual

750/760
Feeder Management Relay

Ground Overcurrent

7–26
original angle. The block alarm should remain throughout the rotation as the
current polarized element is still blocking.
6. Increase the angle of the ground current lagging 3I
are in-phase. The block alarm should remain.
7. Maintaining the ground current angle in-phase with 3I
lagging the V voltage until into the permitted region. The block alarm should
an
disappear when the angle reaches the tripping region.
a) Ground TOC
The procedure to test this element is identical to that outlined in Phase TOC 1 on
page 7–18, except that current is injected into the ground input terminals and the
element is not subject to the "phases required for operation" and "voltage
restrained time overcurrent" checks.
The blocking from logic inputs check is different from that for Phase TOC 1 and is
performed as follows:
1. Inject current to cause a pickup.
2. Assert a logic input to provide a "Block Ground Time". The Pickup LED should
immediately go out.
3. Repeat Steps 1 and 2 for logic inputs "Block Ground O/C", "Block All O/C" and
"Block 1 Trip Relay" as required.
b) Ground IOC
The procedure to test this element is identical to that outlined in Phase TOC 1 on
page 7–18, except that current is injected into the ground input terminals, and the
element is not subject to the "phases required for operation", "linear reset timing",
and "voltage restrained time overcurrent" tests.
The blocking from logic inputs check is different from that for Phase TOC 1 and is
performed as follows:
1. Inject current to cause a pickup.
2. Assert a logic input to provide a "Block Ground Inst". The Pickup LED should
immediately go out.
3. Repeat Steps 1 and 2 for logic inputs "Block Ground O/C", "Block All O/C" and
"Block 1 Trip Relay" as required.
c) Ground Directional OC
The procedure to test this element is identical to that outlined in Neutral Directional
OC on page 7–24, except that the operating current is the ground current. Also,
Ground Directional may only be voltage polarized.
d) Sensitive Ground TOC
The procedure to test this element is identical to that outlined in Phase TOC 1 on
page 7–18, except that current is injected into the sensitive ground input terminals,
and the element is not subject to the "phases required for operation" and "voltage
restrained time overcurrent" tests.
The blocking from logic inputs check is different from that for Phase TOC 1 and is
performed as follows:
1. Inject current to cause a pickup.
2. Assert a logic input to provide a "Blk Sens Gnd Time". The Pickup LED should
immediately go out.
3. Repeat Steps 1 and 2 for logic inputs "Block Sens Gnd O/C", "Block All O/C" and
"Block 1 Trip Relay" as required.
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Protection Schemes
current until the currents
0
increase the angle of 3I
0 0
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