to the protection function through the tap changer position indication function
TPOSYLTC.
Typically, the tap changer is located within the HV winding, that is, winding 1 of the
power transformer. The
Tapped winding
setting parameter specifies whether the
tap changer is connected to winding 1, winding 2 or winding 3. The
Tapped winding
setting parameter is also used to enable or disable the automatic adaptation to the
tap changer position. The possible values are "Not in use", "Winding 1", "Winding 2",
"Winding 3".
There can be only one tap changer in the transformer, that is, the
function can take into account and compensate only for one tap changer.
The
Tap nominal
setting parameter provides the number of the tap which results in
the nominal voltage and current. When the current tap position deviates from this
value, the input current values where the tap changer resides are scaled to match
the currents on the other side.
A correct scaling is determined by the number of steps, the direction of the
deviation from the nominal tap and the percentage change in the voltage resulting
from a deviation of one tap step. The percentage value is set via the
Step of tap
setting.
The operating range of the tap changer is defined by the
Min winding tap
and
Max
winding tap
settings. The
Min winding tap
setting gives the tap position number
resulting from the minimum effective number of winding turns on the side of the
transformer where the tap changer is connected. Correspondingly, the
Max winding
tap
setting gives the tap position number resulting from the maximum effective
number of winding turns.
The
Min winding tap
and
Max winding tap
settings help the tap position
compensation algorithm find the direction of the compensation. This also ensures
that if the current tap position information is corrupted, the automatic tap changer
position adaptation does not try to adapt to any unrealistic position values.
(HV) (LV)
Tap nominal
Min winding tap
Max winding tap
Figure 408: Simplified presentation of the HV and LV windings of a two-winding
transformer with demonstration of the settings Max winding tap, Min winding tap
and Tap nominal
The position value is available in the Monitored data view on LHMI or through
other communication tools in TPOSYLTC. When the quality of the TAP_POS input
value is not good, the position information in the TAP_POS input is not used, and
1MRS759142 F
Protection functions
REX640
Technical Manual
721
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