Current Differential Relay
GARD 8000 SYS RFL Electronics
June 20, 2014 13-75 973.334.3100
Note: The status bit transmission time ranges between 6 and 24 ms with an average of 16 ms.
The status bits are CRC protected for security.
13.5.2.8 DIRECT TRANSFER TRIP
The relays are constantly communicating with each other passing data regarding the measured
currents, addressing, ping-pong, etc. A high priority Direct Transfer Trip (DTT) message is also
included. (For a 3-terminal system, two DTT signals are provided; one for each channel.)
The DTT signal will be received at the remote end and typically mapped to separate output contacts, as
determined by the System Logic.
13.5.2.9 RECLOSER BLOCKING FUNCTION
The GARD 8000 provides a recloser blocking output. The logic is shown in Figure 13-48. This logic
is implemented in the programmable logic processing of the controller module.
The recloser block function is enabled for a period of 3 seconds after the first trip signal is generated
by one of the phases. The user can select if they want to initiate a block for a 2-phase trip or 3-phase
trip condition. The trip output is held for 50ms and then released.
Figure 13-48 Recloser Block Logic
The ‘FORCED 3-POLE TRIP signal is generated by the tripping logic and may be configured to allow
tripping when only the ground generates a trip.
13.5.3 TRIP LOGIC
The GARD 8000 Distance Relay trip logic combines all measuring elements set to produce tripping
into one main TRIP signal.
13.5.3.1 THREE POLE TRIPPING LOGIC
The three pole tripping logic is implemented in the GARD controller’s logic processing and is shown
in Figure 13-49. Each of the phase and ground processing routines has independent outputs to the
logic bus. These signals are latched and then routed to front panel LED indicators. A target reset
function is implemented using the front panel pushbutton.
ALL 3 PHASES
ONE PHASE
Trip PhC
2 or 3 PHASES
RECLOSER BLOCK
TIMER
ATT_DEC = 3000_0
NUMBER =
OUTIN
AT LEAST
TIMER
ATT_DEC = 50_0
NUMBER =
OUTIN
Trip PhA
HAVE TRIPPED
HAVE TRIPPED
Trip PhB
FORCED 3-POLE TRIP
MULTIPHASE RECLOSE BLOCK
HAVE TRIPPED
FORCED 3-POLE TRIP
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