304
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CONTROL ELEMENTS
CHAPTER 7: PROTECTION
RX Coordination Pickup Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.010 seconds
This setting specifies a time delay for the forward-looking protection elements used by
the scheme for coordination with the blocking response from the remote ends. This
setting should include both the response time of the protection elements used to
establish a blocking signal and the total transmission time of that signal including the
relay communications equipment interfacing and the communications channel itself.
Transient Block Pickup Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.030 seconds
This setting specifies a transient blocking mechanism embedded in the directional
comparison blocking scheme for coping with the exposure of both the over-reaching
zone 2 and ground directional overcurrent function to current reversal conditions.
The transient blocking logic applies to the send path only. Identifying the fault as a
reverse fault establishes the blocking signal. If the reverse fault condition prevails for the
time specified by this setting, the blocking operation will be extended by the transient
blocking timer for time specified by the
Transient Block Reset Delay
setting. This allows
riding through current reversal conditions. However, if zone 1 picks up during the
transient blocking condition, the blocking action is removed. This is done to cope with
evolving faults when an external fault is followed by an internal fault. Without the zone 1
feedback, the trip would be unnecessarily delayed.
This setting should not be greater than the fastest possible trip time for faults on an
adjacent line so that the extended blocking action could be established. This should take
into account the pickup time of the reverse-looking elements of the scheme. The delay
defined by this setting should also not be too short in order to avoid locking up a
spurious reverse fault indication that can occur during internal fault conditions.
Transient Block Reset Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.090 seconds
This setting specifies a transient blocking mechanism embedded in the directional
comparison blocking scheme for coping with the exposure of the overreaching
protection functions to current reversal conditions (see also the
Transient Block Pickup
Delay
setting).
This delay should be long enough to cope with transient conditions including not only
current reversals but also spurious negative and zero-sequence currents occurring
during breaker operations (in the case when neutral directional or negative-sequence
directional overcurrent functions are used). Breaker failure time of the surrounding
protection systems within the reach of the ground directional function used by the
blocking scheme should be considered to make sure that the ground directional function
is not jeopardized during delayed breaker operations.
Seal-In Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.000 seconds
The
DIR BLOCK OP
operand is produced according to the directional comparison blocking
scheme logic. This setting defines a minimum guaranteed duration of the
DIR BLOCK OP
pulse. As this operand runs the trip table of the blocking scheme, the
DIR BLOCK TRIP A
,
DIR
BLOCK TRIP B
,
DIR BLOCK TRIP C
, and
DIR BLOCK TRIP 3P
trip operands are sealed-in for the
same period of time.
