Series Compensated Lines; Distance Settings - GE L90 Instruction Manual

CHAPTER 8: APPLICATION OF SETTINGS
forward fault. The time window of allowing the scheme to operate when no
guard was received is the difference between the
default settings, this value is 150 – 8 = 142 ms. This means the scheme is unblocked and can trip during this time window if
a forward fault is sensed.
8.5.7.4 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 (
DCUB FUNCTION
• 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 keys the channel(s) by means of asserting transmit signals
with the aid of the local phase selector or zone 2 distance elements.
DCUB TX4
8.5.7.5 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, keys the carrier(s) during the following conditions:
• The scheme is enabled (
DCUB FUNCTION
• the
DCUB PERMISSIVE ECHO
• the operand that detects the local breaker to be open picks up for a time set by
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 echoes (transmits 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
scheme. As such, if the trip output or breaker control operands (if the breaker control function is used) are used for tripping,
the scheme is fully operational. The permissive key carrier signals
tripping/operating logic, and to output contacts as per the usual L90 logic/output assignments.

8.6 Series compensated lines

8.6.1 Distance settings

Traditionally, the reach setting of an underreaching distance function is set based on the net inductive impedance
between the potential source of the relay and the far-end busbar, or location for which the zone must not overreach. Faults
behind series capacitors on the protected and adjacent lines need to be considered for this purpose. For further
illustration, a sample system shown in the figure is considered.
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
DCUB LOG TRIP WINDOW
signals, are established as follows:
DCUB TX4
is "Enabled" and
is "Enabled" and
setting is "Enabled", and
through is received and any
DCUB RX4
through consist of all normal keying or echo keying conditions.
DCUB TX1 DCUB TX4
C, and
B, DCUB TRIP DCUB TRIP 3P
signal is received when any loss-of-
DCUB RX
and
DCUB LOG PICKUP DELAY
is "Off"), and
DCUB BLOCK
DCUB TX1
is "Off"), and
DCUB BLOCK
to is received, and
LOG1 LOG4
through
DCUB TX1 DCUB TX4
output operands are hard-wired to the trip output
through
DCUB TX1 DCUB TX4
SERIES COMPENSATED LINES
timers. When using
through
DCUB TX1
through transmit
DCUB TX4
LINE END OPEN
operands) the received
must still be assigned to the
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