5–52 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S4 ELEMENTS CHAPTER 5: SETPOINTS
5.6.3.3 Harmonic inhibit
PATH: SETPOINTS S4 ELEMENTS DIFFERENTIAL HARMONIC INHIBIT
This menu contains the percent differential harmonic inhibit settings. This is the percent
differential element in a particular phase if the 2
nd
harmonic of the same phase exceeds
the
HARMONIC INHIBIT LEVEL setpoint. With harmonic inhibit parameters set to
“2nd + 5th”, the RMS sum of the 2
nd
and 5
th
harmonic components is compared against
the level setting. With harmonic averaging enabled, all three phases are inhibited if the 3-
phase average of the harmonics exceeds the level setting.
The 2nd and 5th harmonics are calculated based on W1 three-phase currents. When
HARMONIC AVERAGING is set to Enabled, the relay extracts the 2nd, or the 2nd+5th
harmonics per-phase for all three W1 phases, and calculates average harmonic value. This
value is compared against the level set under
HARMONIC INHIBIT. If HARMONIC AVERAGING
is set to "Disabled", the extracted 2nd, or 2nd+5th harmonics are compared against the
HARMONIC INHIBIT level per each phase individually.
• HARMONIC INHIBIT PARAMETERS: Select “2nd” to compare only the 2
nd
harmonic
current against the
HARMONIC INHIBIT LEVEL. Select “2nd + 5th” to use the RMS sum
of the 2
nd
and 5
th
harmonic components. For most transformers, the 2
nd
harmonic
current alone will exceed 20% during energization and the “2nd” value is sufficient to
inhibit the differential element for inrush current.
• HARMONIC AVERAGING: Select “Enabled” to use the three-phase average of the
harmonic current against the harmonic inhibit setting. For most applications, enabling
harmonic averaging is not recommended.
• HARMONIC INHIBIT LEVEL: Enter the level of harmonic current (2
nd
or 2
nd
+5
th
) above
which the percent differential element will be inhibited from operating. For most
applications, this level should be set to “20%”.
HARMONIC []
INHIBIT
HARMONIC INHIBIT
FUNCTION: Enabled
Range: Enabled, Disabled
MESSAGE
HARMONIC INHIBIT
PARAMETERS: 2nd
Range: 2nd, 2nd + 5th
MESSAGE
HARMONIC AVERAGING:
Disabled
Range: Enabled, Disabled
MESSAGE
HARMONIC INHIBIT
LEVEL: 20.0% f0
Range: 0.1 to 65.0% f
0
in steps of 0.1
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