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5.6 GROUPED ELEMENTS
5
Up to three identical neutral current unbalance elements, one per each installed CT/VT module.
The neutral current unbalance element responds to a differential current signal measured as a vectorial current difference
between neutral currents of parallel banks. In case of ungrounded banks, regular, preferably low-ratio CT can be used. In
case of grounded banks, a window or core-balance CT shall be used for increased accuracy/sensitivity.
The function applies simplified compensation for the inherent bank unbalance. Accurate compensation requires three bal-
ancing factors that are difficult to measure in practical situations. Instead, a simple and practical compensation responding
to both the positive-sequence current and negative-sequence current is applied. This method is easy to apply and remains
accurate as long as the zero-sequence bank currents are relatively small. Under large zero-sequence bank currents, the
applied method of compensation for the inherent bank unbalance is less accurate. The solution to this problem is to use a
small portion of the zero-sequence current at the bank terminals to produce extra restraint and preserve high sensitivity of
this protection method.
By setting both the slope and the inherent unbalance compensating factor to zero one could apply the function as a plain
overcurrent element responding to the split-phase neutral current.
5-136
NTRL CUR UNBALCE 1
MESSAGE
STG 2 PKP: 0.030 pu
NTRL CUR UNBALCE 1
MESSAGE
STG 2 SLOPE: 2.0%
NTRL CUR UNBALCE 1
MESSAGE
STG 3 PKP: 0.040 pu
NTRL CUR UNBALCE 1
MESSAGE
STG 3 SLOPE: 2.0%
NTRL CUR UNBALCE 1
MESSAGE
STG 4 PKP: 0.050 pu
NTRL CUR UNBALCE 1
MESSAGE
STG 4 SLOPE: 5.0%
NTRL CUR UNBALCE 1
MESSAGE
STG 1 DEL: 30.00 s
NTRL CUR UNBALCE 1
MESSAGE
STG 2 DEL: 10.00 s
NTRL CUR UNBALCE 1
MESSAGE
STG 3 DEL:
NTRL CUR UNBALCE 1
MESSAGE
STG 4 DEL:
NTRL CUR UNBALCE 1
MESSAGE
DPO DELAY: 0.25 s
NTRL CUR 1 BLK STG1:
MESSAGE
Off
NTRL CUR 1 BLK STG2:
MESSAGE
Off
NTRL CUR 1 BLK STG3:
MESSAGE
Off
NTRL CUR 1 BLK STG4:
MESSAGE
Off
NTRL CUR UNBALCE 1
MESSAGE
TARGET: Self-Reset
NTRL CUR UNBALCE 1
MESSAGE
EVENTS: Disabled
C70 Capacitor Bank Protection and Control System
Range: 0.001 to 5.000 pu in steps of 0.001
Range: 0.0 to 10.% in steps of 0.1
Range: 0.001 to 5.000 pu in steps of 0.001
Range: 0.0 to 10.% in steps of 0.1
Range: 0.001 to 5.000 pu in steps of 0.001
Range: 0.0 to 10.% in steps of 0.1
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.00 to 600.00 s in steps of 0.01
1.00 s
Range: 0.00 to 600.00 s in steps of 0.01
0.20 s
Range: 0.00 to 600.00 s in steps of 0.01
Range: FlexLogic™ operand
Range: FlexLogic™ operand
Range: FlexLogic™ operand
Range: FlexLogic™ operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
5 SETTINGS
GE Multilin
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