Description of Operation
GARD 8000 Distance Relay
RFL Electronics Inc.
STATION “A” Z2
STATION “B” Z2
BKR
A
BKR
B
+
T2A
“A” Z2
RXA
TRIP BKR A
“A” Z1
TRANSMIT
TRIP B
+
T2B
“B” Z2
RXB
TRIP BKR B
“B” Z1
TRANSMIT
TRIP A
STATION “A” Z1
STATION “B” Z1
STATION “A” Z2
STATION “B” Z2
BKR
A
BKR
B
+
T2A
“A” Z2
RXA
TRIP BKR A
“A” Z1
TRANSMIT
TRIP B
+
T2B
“B” Z2
RXB
TRIP BKR B
“B” Z1
TRANSMIT
TRIP A
STATION “A” Z1
STATION “B” Z1
Figure 9-13. Permissive Underreach Transfer Trip (PUTT)
Permissive Underreach is activated when selected in the Protection Scheme setting. It functions as a
complement to the Step Distance scheme. With this scheme, if a terminal locates the fault inside zone
1 (adjusted below 100% of the line), and the other terminal locates the fault inside zone 2 (adjusted
over 100% of the line), the fault is considered internal to the transmission line; closer to the terminal
that initially detects the fault.
The terminal detecting the fault inside zone 1 will generate an instantaneous tripping signal and
transmit this channel signal to the remote end to allow tripping. If any overreach measuring element
(zone 2 or zone 3) has picked up, the remote terminal will trip instantaneously when the channel signal
is received.
August 1, 2009
9-17
973.334.3100
