Description of Operation
GARD 8000 Distance Relay
RFL Electronics Inc.
The remote breaker open detector is based on if there is a three-phase trip of the remote end during a
non-three-phase fault, the current through any of the phases (one if the fault is phase-to-phase and two
if the fault is single-phase-to-ground) will be very small (capacitive charging current only) while the
remaining phase (s) will continue to detect the fault in zone 2. For this, the unit has an undercurrent
unit whose level is given by the “Min current level” for the Remote Open Breaker function set in
“Breaker settings.”
In case of long lines, the capacitive current could exceed the minimum current setting and then the
setting “Detection by capacitive current” should be used.
The block diagram below shows the operation of the remote breaker open detector logic.
Fault detector
3 phase fault
Zone 1 fault
Trip
Zone 2 fault
Trip Remote Open
Breaker
IA
IB
IC
10 ms
0
Remote open
breaker time
delay
Cap IA
Cap IB
Cap IC
Enable Cap current
T
0
Figure 9-33. Open breaker detector
August 1, 2009
9-36
973.334.3100
