GE D90 Plus Instruction Manual page 197

CHAPTER 7: PROTECTION
NOTE:
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
become self-polarized regardless of other memory voltage logic conditions. When the
selected operand is de-asserted (logic 0), the distance functions follow other conditions
of the memory voltage logic shown below.
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 will produce
a considerable improvement in operating time.
The CVT filter function should be disabled if the T1, T2, and Tx parameters are not known
(the default values should not be used). Contact GE Grid Solutions 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. The CVT filter function should be
disabled if this parameter is not known (the default value should not be used). Contact
GE Grid Solutions for assistance in determining these settings.
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. The CVT filter function should be
disabled if this parameter is not known (the default value should not be used). Contact
GE Grid Solutions for assistance in determining these settings.
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. The CVT filter function should be
disabled if this parameter is not known (the default value should not be used). Contact
GE Grid Solutions for assistance in determining these settings.
The
Force Self-Polarization
asserted simultaneously. If this happens, the logic will give higher priority to forcing self-
polarization as shown in the figure below. 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 may be applied permanently and therefore
should take higher priority.
and
Force Memory Polarization
GROUPED PROTECTION ELEMENTS
settings should never be
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