Harmonic Inhibit - GE 745 TRANSFORMER MANAGEMENT RELAY Instruction Manual

5 SETPOINTS
b) HARMONIC INHIBIT
This section contains the settings of the percent differential harmonic inhibit feature. This the percent differen-
tial element in a particular phase if the 2
setpoint. With harmonic inhibit parameters set to 2nd+5th, the RMS sum of the 2
nents is compared against the level setting. With harmonic averaging enabled, all three phases are inhibited if
the three-phase average of the harmonics exceeds the level setting.
S HARMONIC INHIBIT
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HARMONIC INHIBIT

FUNCTION: Enabled
HARMONIC INHIBIT
PARAMETERS: 2nd
HARMONIC AVERAGING:
Disabled
HARMONIC INHIBIT
LEVEL: 20.0% ƒο
c) ENERGIZATION INHIBIT
Over and above the standard harmonic inhibit feature programmed above, the 745 contains a harmonic inhibit
feature which is in service only during energization and/or sympathetic inrush.
De-energization and energization of the transformer is detected by any of the following three methods:
1. With energization sensing by current enabled, all currents dropping below the minimum energization cur-
rent indicates de-energization; any current exceeding the minimum energization current indicates energi-
zation. This method is the least reliable method of detecting energization, since an energized and
unloaded transformer will be detected as being de-energized if this method is used alone.
2. With energization sensing by voltage enabled, the voltage dropping below the minimum energization volt-
age indicates de-energization; any current exceeding the minimum energization current indicates energi-
zation.
3. With 'b' auxiliary contacts from all switching devices (which can be used to energize the transformer) con-
nected in series to a logic input and assigned to the BREAKERS ARE OPEN setpoint, the contacts closed indi-
cates de-energization; any current exceeding the minimum energization current indicates energization.
Energization inhibit settings are put in service upon detection of de-energization. Upon energization, the ener-
gization inhibit duration timer is initiated and the settings are removed from service when the time delay
elapses.
GE Power Management
nd
harmonic of the same phase exceeds the HARMONIC INHIBIT LEVEL
This message indicates the start of the HARMONIC INHIBIT section. To
continue with these setpoints press
next section.
Range: Disabled / Enabled
Range: 2nd / 2nd + 5th
Select 2nd to compare only the 2
INHIBIT LEVEL. Select 2nd+5th to use the RMS sum of the 2
components. For most transformers, the 2
exceed 20% during energization and the 2nd setting is sufficient to inhibit the
differential element for inrush current.
Range: Disabled / Enabled
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.
Range: 0.1 to 65.0 (steps of 0.1)
Enter the level of harmonic current (2
differential element will be inhibited from operating. For most applications,
this level should be set to 20% .
745 Transformer Management Relay
5.6 S4 ELEMENTS
nd th
and 5 harmonic compo-
, or press
E N TE R
M E SSA G E
nd
harmonic current against the HARMONIC
nd
nd
harmonic current alone will
nd nd th
or 2 +5 ) above which the percent
to go to the
th
& 5 harmonic
5
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