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S4 CONTROLS
Second harmonic inhibit
6–150
The 350 relay can be used for feeder transformer protection. During transformer
energization, the inrush current presenting in phase currents may impact some sensitive
elements, such as neutral directional overcurrent. Therefore, the ratio of the second
harmonic to the fundamental magnitude per phase is monitored. When this ratio exceeds
a set pickup level, an inhibit signal is asserted, which can be used to block such sensitive
elements.
PATH:
SETPOINTS > S4 CONTROLS > 2ND HARMONIC INHIBIT
2ND HARMONIC INHIBIT FUNCTION
Range: Disabled, Latched Alarm, Alarm, Control
Default: Disabled
For details see
Common
PICKUP
Range: 0.1 to 40.0% in steps of 0.1%
Default: 20.0%
DELAY
Range: 0.00 to 600.00 s in steps of 0.01 s
Default: 0.00 s
This setting specifies the time delay after pickup the function waits before operating.
PHASES FOR OP
Range: Any One, Any Two, All Three, Average
Default: Any One
This setting defines the phases required for operation as follows:
ANY ONE: At least one phase picked up.
ANY TWO: Two or more phases picked up.
ALL THREE: All three phases picked up.
AVERAGE: The average of three-phase harmonics picked up.
If set to AVERAGE, the relay calculates the average level of the second 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. Only phases where the fundamental current exceeds the cut-off level are
included in the average.
MIN OP CURRENT
Range: 0.03 to 3.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
This setting specifies the minimum value of fundamental current required to allow the
second harmonic inhibit element to operate.
OUTPUT RELAYS X
For details see
Common
setpoints.
setpoints.
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
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