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5.7 CONTROL ELEMENTS
nal is primarily meant to be the output operand from either the negative-sequence directional or neutral directional
overcurrent elements. As both these elements have separate forward and reverse output operands, the forward indica-
tion should be used (that is,
The selected protection element (or elements in combination) should be coordinated with the selection of
. For all forward external faults seen by an element set as
REV
ing element set as
and to overcome spurious directional element operation during transients, adding at least 0.5 cycles of pickup delay to
the forward directional element is recommended.
•
GND DIR O/C REV: 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 set as
though any FlexLogic operand could be set as
various protection elements or to 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 ele-
ment. As both these elements have separate forward and reverse output operands, the reverse indication should be
used (that is,
NEG SEQ DIR OC1 REV
The selected protection element (or elements in combination) should be coordinated with the selection of
. For all the forward external faults seen by an element set as
FWD
looking element set as
rity and to overcome spurious directional element operation during transients, adding a pickup delay greater than the
pilot channel delay to the reverse directional element is recommended.
•
TRANS BLOCK PICKUP DELAY: This setting defines a transient blocking mechanism embedded in the directional
comparison unblocking scheme for coping with the exposure of both the over-reaching zone 2 and ground directional
5
overcurrent function to current reversal conditions.
The transient blocking logic applies to both operate (trip) and send (transmit) paths. Identifying the fault as a reverse
fault prevents the scheme from both operating and keying the channel. If the reverse fault condition prevails for
BLOCK PICKUP DELAY
BLOCK RESET DELAY
However, if distance zone 1 picks up during the transient blocking condition, the blocking action is removed. This is to
cope with evolving faults when an external fault is followed by an internal fault. Without the zone 1 feedback, the trip
would be delayed unnecessarily.
The
TRANS BLOCK PICKUP DELAY
so that extended blocking action could be established. This should take into account the pickup time of the reverse-
looking elements of the scheme. To avoid locking up a spurious reverse fault indication that can occur during internal
fault conditions, the delay defined by this setting should not be too short.
•
TRANS BLOCK RESET DELAY: This setting defines a transient blocking mechanism embedded in the directional
comparison unblocking scheme for coping with the exposure of the overreaching protection functions to current rever-
sal conditions (see also the
This delay should be selected 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). The breaker failure time of the surround-
ing protection systems within the reach of the ground directional function used by the directional comparison unblock-
ing scheme should be considered to make sure that the ground directional function is not jeopardized during delayed
breaker operations.
•
ECHO DURATION: This setting defines the guaranteed and exact duration of the echo pulse. The duration does not
depend on the duration and shape of the received
up of the transmit/receive loop.
•
ECHO LOCKOUT: This setting defines the lockout period for the echo logic after sending the echo pulse. This setting
enables the relay to avoid oscillations of the echo pulses during an autoreclosure dead-time after clearing an internal
fault.
•
LINE END OPEN PICKUP DELAY: This setting defines the pickup value for validation of the line end open conditions
as detected by the line pickup logic via the
5-318
NEG SEQ DIR OC1 FWD
at the other end should pickup and provide a blocking signal. For greater security
GND DIR O/C REV
GND DIR O/C REV
or
NEUTRAL DIR OC1 REV
at the other end should pickup and provide a blocking signal. For greater secu-
GND DIR O/C REV
value, the blocking operation will be extended by the transient blocking timer for the
value. This allows riding through current reversal conditions.
should not be longer than the fastest possible trip time for faults on an adjacent line
TRANS BLOCK PICKUP DELAY
LINE PICKUP LEO PKP
L90 Line Current Differential System
or
).
NEUTRAL DIR OC1 FWD
at one end of the line, the reverse-look-
GND DIR O/C FWD
, thereby enabling the user to combine responses of
).
GND DIR O/C FWD
setting above).
signals. This setting enables the relay to avoid a permanent lock-
RX
FlexLogic operand. The validated line end open con-
5 SETTINGS
GND DIR O/C
. Even
GND DIR O/C REV
GND DIR O/C
at one end of the line, the reverse-
TRANS
TRANS
GE Multilin
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