CHAPTER 7: PROTECTION GROUPED PROTECTION ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 189
Force Memory Polarization
Range: any FlexLogic operand
Default: OFF
The distance zones can be forced to become memory-polarized through this setting. Any
user-selected condition (any FlexLogic operand) can be configured to force memory
polarization. When the selected operand is asserted (logic 1), the distance functions
become memory-polarized regardless of the positive-sequence voltage magnitude at
this time. When the selected operand is de-asserted (logic 0), the distance functions
follow other conditions of the memory voltage logic.
CVT Filter Function
Range: Disabled, Enabled
Default: Disabled
The CVT filter removes the transient response introduced by capacitively coupled
voltage transformers (CVT), restoring the voltage waveforms to a faithful representation
of the primary system voltage. This allows the distance element to achieve operating
times comparable to those obtained when using magnetic VTs.
The CVT filter function is not required for the distance element operation but produces a
considerable improvement in operating time.
Disable the CVT filter function if the T1, T2, and Tx parameters are not known (do not use
the default values). Contact GE Digital Energy for assistance in determining these
settings.
CVT Filter T1
Range: 0.25 to 10.00 ms in steps of 0.01
Default: 1.00 ms
This setting specifies the T1 parameter of the CVT filter. Disable the CVT filter function if
this parameter is not known (do not use the default value). Contact GE Digital Energy for
assistance in determining this setting.
CVT Filter T2
Range: 0.25 to 10.00 ms in steps of 0.01
Default: 1.00 ms
This setting specifies the T2 parameter of the CVT filter. Disable the CVT filter function if
this parameter is not known (do not use the default value). Contact GE Digital Energy for
assistance in determining this setting.
CVT Filter Tx
Range: 0.25 to 10.00 ms in steps of 0.01
Default: 1.00 ms
This setting specifies the Tx parameter of the CVT filter. Disable the CVT filter function if
this parameter is not known (do not use the default value). Contact GE Digital Energy for
assistance in determining this setting.
NOTE:
Never let the Force Self-Polarization and Force Memory Polarization settings to be asserted
simultaneously. If this happens, the logic gives higher priority to forcing self-polarization as
indicated in the logic diagram. This is consistent with the overall philosophy of distance
memory polarization. The memory polarization cannot be applied permanently but for a
limited time only. The self-polarization can be applied permanently and therefore takes
higher priority.
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