304 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CONTROL ELEMENTS CHAPTER 7: PROTECTION
sequence directional or neutral directional overcurrent element. Both these elements
have separate forward and reverse output operands. Use the reverse indication (NEG SEQ
DIR OC1 REV or NEUTRAL DIR OC1 REV).
Coordinate the selected protection element (or elements in combination) with the
selection of the
Ground Directional OC Forward setting. For all the forward external faults
seen by an element selected by the Ground Directional OC Forward setting at one end of
the line, the reverse-looking element at the other selected by the
Ground Directional OC
Forward
setting end picks up and provide a blocking signal.
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 hybrid permissive over-
reaching transfer trip command on bit 1 (the HYB 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 (HYB POTT
TRIP A, HYB POTT TRIP B, HYB POTT TRIP C, and HYB POTT TRIP 3P).
RX1, RX2, RX3, RX4
Range: any FlexLogic operand
Default: OFF
These settings allow the user to select the FlexLogic operands that represent the receive
signals for the scheme. Typically input contacts interfacing with a signaling system are
used as follows:
– 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
Events
Range: Enabled, Disabled
Default: Enabled
This setting enables and disables the logging of hybrid permissive over-reaching transfer
trip (hybrid POTT) scheme events in the sequence of events recorder.
Echo Condition
Range: any FlexLogic operand
Default: OFF
This setting specifies and applies an echo condition when the
Permissive Echo setting is
“Custom.”
Weak Infeed
Range: Enabled, Custom, Disabled
Default: Disabled
If this setting is “Enabled,” the scheme activates both the keying and operating paths
using a pre-programmed weak infeed logic (see the logic diagram). If this setting is
“Custom,” the weak infeed condition is to be specified by the user via the
Weak Infeed
Condition
setting.
Weak Infeed Condition
Range: any FlexLogic operand
Default: OFF
This setting specifies and applies a weak infeed condition when the
Weak Infeed setting
is “Custom.”
The figure shows the hybrid POTT scheme logic.
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