CHAPTER 7: MONITORING HARMONIC DETECTION
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 7–39
– AVERAGE: The average of three-phase harmonics or THDs picked up.
If set to AVERAGE, the relay calculates the average level of the selected harmonic and
compares this level against the pickup setting. Averaging of the selected harmonic
follows an adaptive algorithm depending on the fundamental current magnitude per-
phase. If the fundamental magnitude on any of the three phases goes below the current
cut-off level, the selected harmonic current from that phase is dropped (zeroed) from the
equation for averaging, and the divider is decreased from 3 to 2. The same happens if
the magnitude of the fundamental magnitude on one of remaining two phases drops
below the cut-off level. In this case the selected harmonic on this phase is dropped from
summation, and the divider is decreased to 1.
MIN OPER CURRENT
Range: 0.03 to 1.00 x CT in steps of 0.01
Default: 0.10 x CT
This setting sets the minimum value of current required to allow the Harmonic Detection
element to operate.
If PHASES FOR OPERATION is set to AVERAGE, the average of three-phase currents is
used for supervision. A similar adaptive average algorithm is applied to calculate the
average of operation current magnitude.
OUTPUT RELAY X
For details see Common Setpoints
.
EVENTS
Range: Disabled, Enabled
Default: Enabled
TARGETS
Range: Self-reset, Latched, Disabled
Default: Self-reset
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