CHAPTER 7: PROTECTION CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 303
Echo Duration
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.100 seconds
This setting specifies the guaranteed and exact duration of the echo pulse. The duration
is not dependent on the duration and shape of received RX signals. This setting enables
the relay to avoid a permanent lock-up of the transmit-receive loop.
Echo Lockout
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.250 seconds
This setting specifies the lockout period for the echo logic after sending the echo pulse.
This enables the relay to avoid oscillations of the echo pulses during an autoreclosure
dead-time after clearing an internal fault.
Seal-In Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.000 seconds
The HYB POTT OP FlexLogic operand is produced according to the hybrid POTT scheme
logic. This setting specifies a minimum guaranteed duration for the HYB POTT OP pulse. As
this operand runs the trip table of the hybrid POTT scheme, the HYB POTT TRIP A, HYB POTT
TRIP B, HYB POTT TRIP C, and HYB 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 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 (both through the
transient blocking logic). Good directional integrity is the key requirement for an over-
reaching forward-looking protection element used for this feature.
Even though any operand can be used for this setting, enabling the user to combine
responses of various protection elements or 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. Use the forward
indication (that is, NEG SEQ DIR OC1 FWD or NEUTRAL DIR OC1 FWD).
Coordinate the selected protection element (or elements in combination) with the
selection of the
Ground Directional OC Reverse setting. For all the forward external faults
seen by an element selected by the Ground Directional OC Forward at one end of the
line, the reverse-looking element at the other end selected by
Ground Directional OC
Reverse
picks up and provides a blocking signal.
Ground Directional OC Reverse
Range: any FlexLogic operand
Default: OFF
This setting defines the FlexLogic operand (if any) of a protection element used in
addition to zone 4 for identifying reverse faults, and thus, for stopping the transmit
signal and initiating the transient blocking timer. Good directional integrity is the key
requirement for a reverse-looking protection element used for this feature.
Even though any operand can be used for this setting, enabling the user to combine
responses of various protection elements or to apply extra conditions through FlexLogic
equations, this extra signal is meant to be the output operand from either the negative
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