Distance Relay Setting Examples
GARD 8000 Distance Relay
RFL Electronics Inc.
8.2.10
21L DCB TIMER SETTINGS
There are two timer settings associated with DCB; Dist coord time and DCB dist delay time.
Dist coord time
extends the blocking signal (carrier start) from the reverse Z4 (note that the timer does
not operate on the non-directional Fast carrier start as the latter will assert for forward faults as well).
The recommended setting is 20 ms.
DCB dist delay time
is the time the forward pilot zone has to wait for a blocking signal before it is
allowed to issue a trip. When using Fast carrier start, this timer can be set to 0, if extra high speed fault
clearing is required. However, a more conservative setting of 10 ms is recommended. When not
applying Fast Carrier start 10 ms is recommended.
Note that these times assumed that the communication channel is a GARD ON/OFF carrier. Other
carrier sets may have different drop-out characteristics that will have to be considered. In addition, a
distance relay of different design at the remote end may warrant longer time delay settings.
Channel receive
Forward pilot zone
Out -of-step Block
Block pilot trip
Input channel stop
Zone 1 Fault
Enable OSB pilot
Distance pilot protection
trip
Distance protection
channel start
50P-1 Phase A
Reverse pilot zone (Z4)
50P-1 Phase B
50P-1 Phase C
50G-1 Ground
Fast carrier start
0
T
Dist Coord Time
Distance protection
channel stop
T
0
DCB dist delay
time
Figure 8-3. Directional Comparison Blocking (DCB) Distance Relay Scheme
August 1, 2009
8-27
973.334.3100
