GE L90 Instruction Manual page 603

10 APPLICATION OF SETTINGS
c) LOSS-OF-GUARD OPERATION
The loss-of-guard operation picks under the following conditions:
• The scheme is enabled (
• any loss-of-guard signal is received without its associated
• a fault is seen in the forward zone 2 distance elements or ground directional forward function (if configured), and
• the reverse zone 4 distance elements or ground directional reverse function (if configured) did not pickup to set the
transient blocking.
If these conditions are met, then the
operating the scheme and asserting the
tor and loss-of-guard signals will determine what tripping operands will be operated. The
allows for any and all channel(s) to transition from guard to permissive before operating due to loss-of-guard in the pres-
ence of a forward fault. The time window of allowing the scheme to operate when no
loss-of-guard was received is the difference between the
When using default settings, this value is 150 – 8 = 142ms. This means the scheme is unblocked and can trip during this
time window if a forward fault is sensed.
d) KEYING OF THE CARRIER(S) UNDER NORMAL CONDITIONS
The keying signals, which allows the relay to key the permissive channel during normal permissive scheme operation by
means of the through
DCUB TX1
• The scheme is enabled (
• a fault is seen in the forward zone 2 distance elements or ground directional forward function (if configured), and
• the reverse zone 4 distance elements or ground directional reverse function (if configured) did not pickup to set the
transient blocking.
If these conditions are met, then the scheme will key the channel(s) by means of asserting transmit signals
through with the aid of the local phase selector or zone 2 distance elements.
DCUB TX4
e) KEYING OF THE CARRIER DURING ECHO CONDITIONS
The echo signal, which allows the relay to key the permissive channel(s) through the
operands during echo conditions when the local breaker opened, will key the carrier(s) during the following conditions:
• The scheme is enabled (
• the
DCUB PERMISSIVE ECHO
• the
LINE PICKUP LEO PKP
, and
PICKUP DELAY
• any permissive signal
DCUB RX1
• a fault is not seen in the forward zone 2 distance elements or ground directional forward function (if configured) for at
least 100 ms, and
• the reverse zone 4 distance elements or ground directional reverse function (if configured) did not pickup to set the
transient blocking.
If these conditions are met, then the scheme will echo (transmit the
permissive signal(s) back to the remote relay based on the echo table.
DCUB RX
The keying or transmit signals
The scheme ,
DCUB TRIP A DCUB TRIB B
scheme. As such, if the trip output or breaker control operands (if the breaker control function is used) are used for tripping,
the scheme fully operational. The permissive key carrier signals
tripping/operating logic, and to output contacts as per the usual L90 logic/output assignments.
GE Multilin
is "Enabled" and
DCUB FUNCTION
DCUB LOG PICKUP DELAY
FlexLogic™ operand. The trip table with the aid of the local phase selec-
DCUB OP
signals, are established as follows:
DCUB TX4
is "Enabled" and
DCUB FUNCTION
is "Enabled" and
DCUB FUNCTION
setting is "Enabled", and
operand that detects the local breaker to be open picks up for a time set by
through is received and any
DCUB RX4
through
DCUB TX1 DCUB TX4
, , and
DCUB TRIP C
L90 Line Current Differential System
10.5 PROTECTION SIGNALING SCHEMES
is "Off"), and
DCUB BLOCK
signal, and
RX
timer is started. After this timer times out, the trip table is run,
DCUB RX
and
DCUB LOG TRIP WINDOW
is "Off"), and
DCUB BLOCK
DCUB TX1
is "Off"), and
DCUB BLOCK
to
LOG1 LOG4
through
DCUB TX1 DCUB TX4
consist of all normal keying or echo keying conditions.
output operands are hard-wired to the trip output
DCUB TRIP 3P
through
DCUB TX1 DCUB TX4
timer
DCUB LOG PICKUP DELAY
signal is received when any
timers.
DCUB LOG PICKUP DELAY
DCUB TX1
through transmit
DCUB TX4
LINE END OPEN
is received, and
operands) the received
must still be assigned to the
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