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10.6 PROTECTION SCHEMES
This procedure verifies that the Restricted Ground Fault performance matches the in-service settings. The
ground element measures the current signal connected to the ground current input CT, H10 and G10 or F12
and E12. The neutral (3 I
rent into one phase automatically produces a neutral current (i.e. 3 I
found under:
SETPOINTS/S4 ELEMENTS/RESTRICTED GROUND/W1 RESTD GND FAULT/...
a) WINDING #1 ELEMENT
To ensure that only the Restricted Ground Fault element operates the trip relays (and any other output relays
selected by the logic) disable all protection features except Restricted Ground Fault.
Using a current supply as shown in the figure below, connect the I
the Winding 1 phase current element and I
ment. Monitor the appropriate output relays as per the relay FlexLogic settings.
b) PICKUP LEVEL
1. With the interval timer disabled, apply the current signal feeding the phase current element and increase
its magnitude slowly until the trip relay, and all the selected auxiliary relays, operate. The operate level
should correspond to the pickup setting in:
SETPOINTS/S4 ELEMENTS/RESTRICTED GROUND/W1 RESTD GND FAULT/W1 RESTD GND FAULT PICKUP
2. When the element operates, check that the TRIP, GROUND and PICKUP LEDs are on and the following
message is displayed:
SS LATCHED (OPERATE):
SS W1 Restd Gnd Fault
3. Reduce the current until the element resets. The reset level should be 97% of the operate level. When the
element resets, the TRIP and message indicators should remain on if the TARGET was selected as
latched. Otherwise, only the TRIP indicator should remain on.
10
4. Reset indicators and clear messages.
10-30
) current is calculated from the vector sum of the three phase currents. Injecting cur-
o
to terminals G10 and H10 as shown for the ground current ele-
2
Figure 10–10: RESTRICTED GROUND TEST SETUP
745 Transformer Management Relay
10 COMMISSIONING
10.6.13 RESTRICTED GROUND FAULT
= I
). Settings for these elements are
o
A
current source to terminals H1 and G1 for
1
GE Power Management
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