CHAPTER 7: PROTECTION CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 299
Line End Open Pickup Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.050 seconds
This setting specifies the pickup value for validation of the line end open conditions as
detected by the line pickup logic through the LINE PICKUP LEO PKP FlexLogic operand. The
validated line end open condition is a requirement for the POTT scheme to return a
received echo signal (if the echo feature is enabled). This value should take into account
the principle of operation and settings of the line pickup element.
Seal-In Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.000 seconds
The POTT OP FlexLogic operand is produced according to the POTT scheme logic. A seal-
in time delay is applied to this operand for coping with noisy communication channels.
This setting defines a minimum guaranteed duration of the POTT OP pulse. As this
operand activates the trip table of the POTT scheme, the POTT TRIP A, POTT TRIP B, POTT TRIP
C, and POTT TRIP 3P trip operands are sealed-in for the same period of time.
Ground Directional OC Forward
Range: any FlexLogic operand
Default: OFF
This setting defines the FlexLogic operand (if any) of a protection element that is used in
addition to zone 2 for identifying faults on the protected line, and thus, for keying the
communication channel and initiating operation of the scheme. Good directional
integrity is the key requirement for an over-reaching forward-looking protection element
used for this setting. Even though any FlexLogic operand can be assigned to this setting,
allowing the user to combine responses of various protection elements or apply extra
conditions through FlexLogic equations, this extra signal is meant to be the output
operand from either the negative-sequence directional overcurrent or neutral
directional overcurrent element. Both of these elements have separate forward and
reverse output operands. The forward indication needs to be used (NEG SEQ DIR OC1 FWD
or NEUTRAL DIR OC1 FWD).
Communication Bits
Range: 1, 2, 4
Default: 1
This setting specifies the number of bits of the communications channel available for the
scheme. With only one bit available, the scheme sends the permissive over-reaching
transfer trip command on bit 1 (the POTT TX1 operand) and responds to the direct trip
command received on bit 1 (the
RX1 setting). The scheme uses only local fault type
identification provided by the phase selector to assert the trip operands (POTT TRIP A, POTT
TRIP B, POTT TRIP C, and POTT TRIP 3P).
RX1, RX2, RX3, RX4
Range: any FlexLogic operand
Default: OFF
These settings select the FlexLogic operands that represent the receive signals for the
scheme. Typically input contacts interfacing with a signaling system are used in the
following manner:
– In single-bit applications,
RX1 must be used
– In two-bit applications,
RX1 and RX2 must be used
– In four-bit applications,
RX1 through RX4 must be used
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