GE L90 Instruction Manual page 614

CONTROL ELEMENTS
BLOCK RX CO-ORD PKP DELAY
scheme for coordination with the blocking response from the remote end(s). In this setting, 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.
TRANS BLOCK PICKUP DELAY
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
transient blocking timer for
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 is unnecessarily
delayed.
Do not set the
TRANS BLOCK PICKUP DELAY
extended blocking action can be established. Take into account the pickup time of the reverse-looking elements of the
scheme. Do not set the delay too short, in order to avoid locking up a spurious reverse fault indication that can occur
during internal fault conditions.
TRANS BLOCK RESET DELAY
coping with the exposure of the overreaching protection functions to current reversal conditions (see also the
).
PICKUP DELAY
Set this delay 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). Consider breaker failure time of the surrounding protection systems
within the reach of the ground directional function used by the blocking scheme, to make sure that the ground directional
5
function is not jeopardized during delayed breaker operations.
BLOCK SCHEME SEAL-IN DELAY
logic. The
BLOCK SCHEME SEAL-IN DELAY
runs the Trip Table of the Blocking scheme, the trip operands
of time.
— This setting defines the FlexLogic operand (if any) of a protection element used in addition to zone 2 for
GND DIR O/C FWD
identifying faults on the protected line, and thus, for initiating operation of the scheme. Good directional integrity is the key
requirement for an over-reaching forward-looking protection element used as
Even though any FlexLogic operand can be used as
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 elements. Both these
elements have separate forward (FWD) and reverse (REV) output operands.
The forward indication is used (
(or elements in combination) with the selection of G
used as
GND DIR O/C FWD
picks up and provides a blocking signal. For greater security 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.
— This setting defines the FlexLogic operand (if any) of a protection element that is used in addition to
GND DIR O/C REV
zone 4 for identifying reverse faults, and thus, for initiating the blocking signal. Either reverse-looking directional or non-
directional overcurrent protection element can be used as
Even though any FlexLogic operand can be used as
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, neutral directional, or a non-directional instantaneous
overcurrent element.
5-390
— This setting defines a delay for the forward-looking protection elements used by the
— This setting defines a transient blocking mechanism embedded in the blocking scheme for
TRANS BLOCK PICKUP DELAY
. This allows riding through current reversal conditions. However, if
TRANS BLOCK RESET DELAY
longer than the fastest possible trip time for faults on an adjacent line so that the
— This setting defines a transient blocking mechanism embedded in the blocking scheme for
— The output FlexLogic operand
defines a minimum guaranteed duration of the
GND DIR O/C FWD
or
NEG SEQ DIR OC1 FWD
ND DIR O/C REV
at one end of the line, the reverse-looking element used as
GND DIR O/C REV
, the blocking operation is extended by the
(DIR BLOCK OP) is produced according to the Blocking scheme
A, B, C, and
DIR BLOCK TRIP
GND DIR O/C FWD
enabling the user to combine responses of various
). Coordinate the selected protection element
NEUTRAL DIR OC1 FWD
. For all the forward external faults seen by an element
.
GND DIR O/C REV
, enabling the user to combine responses of various
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
TRANS BLOCK
pulse. As this operand
DIR BLOCK OP
are sealed-in for the same period
3P
.
at the other end
GND DIR O/C REV