GE D90 Plus Instruction Manual page 309

CHAPTER 7: PROTECTION
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Ground Directional OC Forward
Range: any FlexLogic™ operand
Default: OFF
This setting selects the FlexLogic™ operand (if any) of a protection element used in
addition to zone 2 for identifying faults on the protected line, and thus, for initiating
operation of the scheme. Good directional integrity is the key requirement for an over-
reaching forward-looking protection element used for this feature.
Even though any operand could be used, enabling the user to combine responses of
various protection elements or to apply extra conditions through FlexLogic™ equations,
this extra signal is primarily meant to be the output operand from either the negative-
sequence directional or neutral directional overcurrent elements. Both these elements
have separate forward and reverse output operands.
The forward indication should be used (that is,
FWD). The selected protection element (or elements in combination) should be
coordinated with this setting. For all the forward external faults seen by an element
selected by the
Ground Directional OC Forward
reverse-looking element selected by the
other end should pickup and provide a blocking signal.
Ground Directional OC Reverse
Range: any FlexLogic™ operand
Default: OFF
This setting selects the FlexLogic™ operand (if any) of a protection element that is used
in addition to zone 4 for identifying reverse faults, and thus, for initiating the blocking
signal. Either reverse-looking directional or non-directional overcurrent protection
element may be used for this feature.
Even though any operand could be used, enabling the user to combine responses of
various protection elements or to apply extra conditions through FlexLogic™ equations,
this extra signal is primarily meant to be the output operand from either the negative-
sequence directional, neutral directional, or a non-directional instantaneous overcurrent
element.
The selected protection element (or elements in combination) should be coordinated
with the selection of the
external faults seen by an element selected by the
setting at one end of the line, the reverse-looking element selected by the
setting at the other end should pickup and provide a blocking
Directional OC Reverse
signal.
Communication Bits
Range: 1, 2, 4
Default: 1
This setting specifies the number of bits of the communications channel available for the
directional comparison blocking scheme. With only one bit available, the scheme sends
the blocking signal by asserting the
used to start the channel (set the blocking signal). On internal faults, the scheme
removes the blocking signal by asserting the
For tripping, the directional comparison blocking scheme responds to lack of the
blocking signal on bit 1 (selected by the
type identification provided by the phase selector to assert the
BLOCK TRIP B, DIR BLOCK TRIP
To take advantage of the four-bit blocking scheme, the blocking signals should be
initiated from a disturbance detector. This can be accomplished by using both 50DD and
the operand to assert the blocking signal. Subsequently, specific bits will
DIR BLOCK TX INIT
NEG SEQ DIR OC1 FWD
setting at one end of the line, the
Ground Directional OC Reverse
Ground Directional OC Forward
DIR BLOCK TX INIT
DIR BLOCK TX1
setting). The scheme uses only local fault
RX1
C, and
DIR BLOCK TRIP 3P
CONTROL ELEMENTS
or
NEUTRAL DIR OC1
setting at the
setting. For all the forward
Ground Directional OC Forward
Ground
operand. This operand should be
FlexLogic™ operand.
DIR BLOCK TRIP
output operands.
A, DIR
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