GE Multilin
745 Transformer Management Relay
5-45
5 SETPOINTS
5.6 S4 ELEMENTS
5
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 current indicates
de-energization; any current exceeding the minimum energization current indicates energization. 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 voltage indicates
de-energization; any
current
exceeding the minimum energization current indicates energization.
3.
With ‘b’ auxiliary contacts from all switching devices (which can be used to energize the transformer) connected in
series to a logic input and assigned to the
BREAKERS ARE OPEN
setpoint, the contacts closed indicates 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 energization inhibit
duration timer is initiated and the settings are removed from service when the time delay elapses. The energization inhibit
feature may also be put in service during sympathetic inrush. The onset of sympathetic inrush is detected via a close com-
mand to the parallel transformer switching device connected to a logic input, assigned to the
PARALL XFMR BRKR CLS
set-
point. Energization inhibit settings are put in service when the contact closes. Upon signal removal, the energization inhibit
duration timer is initiated and the settings are removed from service when the time delay elapses.
In a breaker-and-a-half scheme, where current can be present in the CTs without being present in the transformer winding,
it may be necessary to use the Parallel Transformer Breaker Close contact to initiate Energization Inhibit.
•
ENERGIZATION INHIBIT PARAMETERS
: Select "2nd" to compare the 2
nd
harmonic current against
HARMONIC
INHIBIT LEVEL
. Select "2nd + 5th" to use the RMS sum of the 2
nd
and 5
th
harmonics.
•
HARMONIC AVERAGING
: Select "Enabled" to use the three-phase average of the harmonic current against the har-
monic inhibit setting.
•
ENERGIZATION INHIBIT LEVEL
: Enter the level of harmonic current (2
nd
or 2
nd
+ 5
th
) above which the percent differ-
ential element is inhibited from operating. This setting will often need to be set significantly lower than the
HARMONIC
INHIBIT LEVEL
, especially when used with the "Parallel Xfmr BkrCls" logic input function for sympathetic inrush.
•
ENERGIZATION INHIBIT DURATION
: Enter the time delay from the moment of energization (or the end of the parallel
breaker close command) before the energization inhibit feature is removed from service.
•
ENERGIZATION SENSING BY CURRENT
: Select “Enabled” to detect de-energization by the level of all currents drop-
ping below the minimum energization current.
•
MINIMUM ENERGIZATION CURRENT
: Enter the current level below which the transformer is considered de-ener-
gized (energization sensing by current enabled), and above which the transformer is considered energized (any ener-
gization sensing enabled).
•
ENERGIZATION SENSING BY VOLTAGE
: Select “Enabled” to detect de-energization by the level of the voltage drop-
ping below the minimum energization voltage. This setpoint is displayed only if
S2 SYSTEM SETUP
ÖØ
VOLTAGE INPUT
Ö
VOLTAGE SENSING
is “Enabled”.
•
MINIMUM ENERGIZATION VOLTAGE
: Enter the voltage level below which the transformer is considered de-ener-
gized (when
ENERGIZATION SENSING BY VOLTAGE
is “Enabled”). This setpoint is displayed only if
S2 SYSTEM SETUP
ÖØ
VOLTAGE INPUT
Ö
VOLTAGE SENSING
is “Enabled”.
•
BREAKERS ARE OPEN SIGNAL
: Select any logic input which, when asserted, indicates to the 745 that the trans-
former is de-energized. The selected logic input should be connected to the auxiliary contacts of the transformer
breaker or disconnect switch.
•
PARALL XFMR BRKR CLS SIGNAL
: Select any logic input which, when asserted, will indicate to the 745 the onset of
sympathetic inrush. The selected logic input should be connected to the close command going to the parallel trans-
former switching device.
Содержание TRANSFORMER MANAGEMENT RELAY 745
Страница 2: ...Courtesy of NationalSwitchgear com ...