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GRL150 provides the function to check the frequency of communication failures. The function
has FERALM, FERAEN and CF-PER settings, and FER, CF and CF-L counts are displayed as a
result of the checking. The function is maily used to check a quality of the pilot wire
communication route. If the FER (Frame Error Rate) exceeds the FERALM setting value, the
FER_ALM alarm signal is output. The FER is calculated by the following equation:
FER: Frame Error Rate
FER = {CF-L / (The number of received frame for CF-PER period)} × 100 (%)
CF:
counts the number of communication failure occurrence for every sampling time.
CF-L: records and displays the number of communication failure occurrence for CF-PER
setting.
The CF-L is used when the failure is out of count. (See Section 4.2.3.4 and 4.2.6.5.)
CF-PER:
period time setting for counting up the communication failure.
The FER can be disabled by the scheme switch [FERAEN].
3.3.6
Disconnector Monitoring
The disconnector is monitored because the disconnector contact signal is used for the
out-of-service terminal detection.
To monitor the disconnector, one pair of normally open contact and normally closed contact is
introduced. Disconnector failure is detected when both contacts are simultaneously in the open or
closed state for the prescribed period.
The monitoring is blocked by setting the scheme switch [DSSMEN] to OFF. The default setting of
[DSSMEN] is OFF to prevent a false failure detection when the disconnector contacts are not
introduced.
3.3.7
Circuit Breaker Monitoring
The relay provides the following circuit breaker monitoring functions.
Circuit Breaker State Monitoring
Circuit breaker state monitoring is provided for checking the health of circuit breaker (CB). If two
binary inputs are programmed to the functions 'CB_N/O_CONT' and 'CB_N/C_CONT', then the
CB state monitoring function becomes active. In normal circumstances these inputs are in opposite
states. Figure 3.3.7.1 shows the scheme logic. If both show the same state during five seconds,
then a CB state alarm CBSV operates and "Err:CB" and "CB err" are displayed in LCD message
and event record message respectively.
The monitoring can be enabled or disabled by setting the scheme switch [CBSMEN].
FER > "FERALM"
setting value
[FERAEN]
"ON"
+
Figure 3.3.5.1 Frame Error Rate Alarm
⎯
1374
FER_ALM
&
⎯
62
6 F 2 S 0 8 2 8
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