GE C70 Instruction Manual page 289

5 SETTINGS
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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.
GE Multilin
NTRL CUR UNBALCE 1
STG 2 PKP: 0.030 pu
NTRL CUR UNBALCE 1
STG 2 SLOPE: 2.0%
NTRL CUR UNBALCE 1
STG 3 PKP: 0.040 pu
NTRL CUR UNBALCE 1
STG 3 SLOPE: 2.0%
NTRL CUR UNBALCE 1
STG 4 PKP: 0.050 pu
NTRL CUR UNBALCE 1
STG 4 SLOPE: 5.0%
NTRL CUR UNBALCE 1
STG 1 DEL: 30.00 s
NTRL CUR UNBALCE 1
STG 2 DEL: 10.00 s
NTRL CUR UNBALCE 1
STG 3 DEL: 1.00 s
NTRL CUR UNBALCE 1
STG 4 DEL: 0.20 s
NTRL CUR UNBALCE 1
DPO DELAY: 0.25 s
NTRL CUR 1 BLK STG1:
Off
NTRL CUR 1 BLK STG2:
Off
NTRL CUR 1 BLK STG3:
Off
NTRL CUR 1 BLK STG4:
Off
NTRL CUR UNBALCE 1
TARGET: Self-Reset
NTRL CUR UNBALCE 1
EVENTS: Disabled
C70 Capacitor Bank Protection and Control System
5.6 GROUPED ELEMENTS
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
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: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
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