GE Power Management
745 Transformer Management Relay
5-49
5 SETPOINTS
5.6 S4 ELEMENTS
5
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
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 compo-
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.
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.
y
HARMONIC INHIBIT
y
[ENTER] for more
This message indicates the start of the
HARMONIC INHIBIT
section. To
continue with these setpoints press
, or press
to go to the
next section.
HARMONIC INHIBIT
FUNCTION: Enabled
Range: Disabled / Enabled
HARMONIC INHIBIT
PARAMETERS: 2nd
Range: 2nd / 2nd + 5th
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
& 5
th
harmonic
components. For most transformers, the 2
nd
harmonic current alone will
exceed 20% during energization and the
2nd
setting is sufficient to inhibit the
differential element for inrush current.
HARMONIC AVERAGING:
Disabled
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.
HARMONIC INHIBIT
LEVEL: 20.0%
ƒο
Range: 0.1 to 65.0 (steps of 0.1)
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%
.
E N TE R
M E SSA G E
Summary of Contents for 745 TRANSFORMER MANAGEMENT RELAY
Page 30: ...2 8 745 Transformer Management Relay GE Power Management 2 3 SECURITY 2 GETTING STARTED 2 ...
Page 210: ...7 36 745 Transformer Management Relay GE Power Management 7 2 BLOCK DIAGRAMS 7 SCHEME LOGIC 7 ...
Page 322: ...9 12 745 Transformer Management Relay GE Power Management 9 3 USING 745PC 9 745 PC SOFTWARE 9 ...
Page 396: ...A 4 745 Transformer Management Relay GE Power Management A 1 FIGURES AND TABLES APPENDIXA A ...
Page 400: ...C 2 745 Transformer Management Relay GE Power Management C 1 WARRANTY INFORMATION APPENDIXC C ...
Page 406: ...vi 745 Transformer Management Relay GE Power Management ...
Page 407: ...GE Power Management 745 Transformer Management Relay NOTES ...