GE D90 Plus Instruction Manual page 438

AUTOMATION LOGIC
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Figure 359: 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 360: 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 361: 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.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 8: AUTOMATION