486 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
AUTOMATION LOGIC CHAPTER 8: AUTOMATION
Figure 423: Raise command automation logic
The following automation logic detects excessive tap changer operations. First, a TIMEOUT
signal is created that produces a one second pulse once an hour.
Figure 424: Timeout signal automation logic
A counter is then implemented to accumulate the number of operations (indicated by the
OFF TAP signal). The value of OP COUNT is reset to zero by the TIMEOUT signal once per
hour.
Figure 425: Operation counter automation logic
If the number of operations is equal to or greater than the maximum number of permitted
operations (30 in this example), then a MAX OP/HOUR alarm is declared.
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