Current Differential Relay
GARD 8000 SYS RFL Electronics
June 20, 2014 13-41 973.334.3100
Relay Configuration Mismatch
There are a number of key setup and configuration parameters that need to be the same on both ends of
the line being protected. The current differential relay compares these parameters and if they do not
match this indicator is set to red. When they match the indicator is set to green.
The parameters that must match include:
50 Hz /60 Hz line
Two-terminal / three terminal relay configuration
Single-pole / three-pole configuration
The local and remote CT factor settings in both relays must agree
Pong-Pong
This is the unidirectional channel delay (in ms) as measured by the ping-pong tests. The ping-pong is
calculated based on a bidirectional measurement; the displayed result is half of the bidirectional
measurement.
Pong-Pong Alarm
When red this indicates that the ping-pong measurements made by the local and remote relays do not
match. The ping-pong is a bidirectional measurement and should provide the same result when either
relay initiates the test. If the two measurements differ by more than 3 ms the error flag is set.
Green indicates the ping-pong tests are the same.
BER
This is an approximation of the communications channel bit error rate (BER). It is most accurate for
modest BER’s (between 2E-5 and 8E-3).
Comms Alarm
When red this indicates an alarm condition in the communications channel. Green indicates the
absence of an alarm condition.
Comms Failure
When red this indicates a failure in the communications channel. Green indicates the absence of a
failure condition.
Timestamp Synched
Red indicates that the real-time clock on the remote system is not synchronized with the local clock.
Green indicates that the two clocks are synchronized.
Guard Before Trip Not Satisfied
When red this indicates that the guard before trip criteria has not been satisfied and the relay will not
trip in primary protection mode. Green indicates that either the criteria have been satisfied or guard
before trip has been disabled by the user.
Hot Standby Active Channel
When red this indicates that the hot standby channel is inactive, green indicates that the channel is
active.
13.4.4 TRANSFERRED STATUS
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