RFL Electronics GARD 8000, Инструкция по эксплуатации

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Description of Operation
GARD 8000 Distance Relay RFL Electronics Inc.
9.2.6 DIRECTIONAL COMPARISON BLOCKING (DCB)
DCB is operating on the principle to use a communication channel to block tripping for external faults
while no signal transfer is required for internal faults. This scheme is typically applied with ON/OFF
Power Line Carrier and has the advantage of not being affected by a possible loss-of-signal for faults
internal to the line. Power Line Carrier transmission uses the power line itself and there is a risk of a
transmitted signal being shorted or interrupted by a fault on the same conductor or line.
The DCB scheme with directional start uses a reverse directional element to start and maintain a carrier
block signal. The scheme requires a channel coordination timer, and a reverse distance zone (Zone 4).
The coordination timer should be adjusted to accommodate maximum expected channel delay plus a
margin to allow for variations of the pick up time of the forward pilot zone and the reverse blocking
element.
21R (CARRIER TX)
21P
21R (CARRIER TX)
BKR
A
BKR
B
TRIP BKR A
CARRIER TX
+
CARRIER
RX
T2A
21R
21P
TRIP BKR B
CARRIER TX
+
CARRIER
RX
T2B
21R
21P
coordination
timer
coordination
timer
21P
21R (CARRIER TX)
21P 21P
21R (CARRIER TX)
BKR
A
BKR
B
TRIP BKR A
CARRIER TX
+
CARRIER
RX
T2A
21R
21P
TRIP BKR B
CARRIER TX
+
CARRIER
RX
T2B
21R
21P
coordination
timer
coordination
timer
21P 21P
Figure 9-18. Directional Comparison Blocking With Directional Carrier TX
Directional Comparison is activated when selected in the Protection Scheme setting. It will function as
a complement to the Step Distance scheme.
The main difference between this scheme and the others is that the channel signal is transmitted to
block remote tripping instead of permitting it. Proper operation of this scheme requires that the
measuring element used to activate the channel be selected as reverse. Therefore, if directional
comparison is selected as the protection scheme, Zone 4 will be set as reverse, even if the setting is
selected as forward.
August 1, 2009 9-21 973.334.3100