Distance Relay Setting Examples
GARD 8000 Distance Relay
RFL Electronics Inc.
Description Range
Units
Step
Actual
49 Thermal Memory
If thermal memory is set to Yes, the function retains
the last calculated thermal level in memory and uses
this as start level when the GARD 8000 is put back
into service.
No - Yes
-
1
No
49 Reset Threshold
Thermal image reset level in % of alarm level.
50 - 100
%
1
80
8.2.9
DISTANCE ELEMENTS – PILOT (COMMS SCHEME) SETTINGS
The standard Directional Comparison Scheme uses a forward pilot zone (Z2 or Z3) and a reverse
blocking zone (Z4). However, this scheme can be complemented with non-directional overcurrent start
elements, Fast Carrier Start.
Carrier start (blocking signal) is issued when the non-directional 50-P1 and 50-G1 (Fast carrier start)
or when the reverse Z4 operates. The drop out of the Z4 signal is delayed by the time set on “Dist
Coord Time.”
Trip is issued when the forward pilot zone (Z2 or Z3) asserts, after the set pickup delay “DCB dist
delay time.” AND no block signal (channel receive) is present. This indicates a forward fault, within
set pilot zone reach.
Carrier stop is issued when the forward pilot zone asserts, Z1 picks up or a pilot trip is issued. This
indicates a forward fault.
8.2.9.1
FAST CARRIER START
Fast Carrier Start is mainly used for one of two reasons:
1.
Coordination with a remote E/M scheme that lacks channel coordination timer and has
measuring elements of an “inverse” characteristic. The operating times of E/M distance relays
are very dependent on settings (taps) and fault conditions while a microprocessor relay exhibits
a more “flat” characteristic. In order to ensure that a block signal will be issued fast enough to
block a remote E/M relay, non-directional overcurrent start is beneficial.
2.
Shorter channel coordination time setting (DCB dist delay time). When Fast Carrier Start is
used, the timer (DCB dist delay time) can be set to 0. This means that trip for internal faults
will take place as soon as the forward pilot zone has detected the fault, without any additional
delay.
Note that when Fast Carrier Start and 67 DCB are used, there are common elements and settings need
to be coordinated. This coordination is covered in the last section in this document. If “Fast carrier
start” is set to “NO,” the 50P-1 and 50G-1 elements are not used in the 21L DCB scheme.
For the majority of applications, where the remote relay is of comparable design, Fast Carrier Start is
not required. The most common way for DCB today is to have directional start (Z4) only.
August 1, 2009
8-25
973.334.3100
