CHAPTER 7: PROTECTION
CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
301
these elements have separate forward and reverse output operands. The reverse
indication should be used (that is,
NEG SEQ DIR OC1 REV
or
NEUTRAL DIR OC1 REV
).
The selected protection element (or elements in combination) should be coordinated
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 should pickup 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 an 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 (refer to the logic diagram below). 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 hybrid permissive over-reaching transfer trip (hybrid POTT) scheme logic is shown
below.