ABB RELION REX640 Technical Manual page 603

1MRS759142 C
REX640
Technical Manual
Compensation of tap changer position
The position of the tap changer used for voltage control can be compensated and the
position information is provided for the protection function through the tap position
indication function TPOSYLTC.
Typically, the tap changer is located within the high voltage winding, that is, winding
1, of the power transformer. The Tapped winding parameter specifies whether the tap
changer is connected to the high voltage side winding or the low voltage side winding.
This parameter is also used to enable and disable the automatic adaptation to the tap
changer position. The possible values are "Not in use", "Winding 1" or "Winding 2".
The Tap nominal parameter tells 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 on the side 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 and the direction of the
deviation from the nominal tap and the percentage change in voltage resulting from a
deviation of one tap step. The percentage value is set using the Step of tap parameter.
The operating range of the tap changer is defined by the Min winding tap and Max
winding tap parameters. The Min winding tap parameter tells the tap position number
resulting in the minimum effective number of winding turns on the side of the
transformer where the tap changer is connected. Correspondingly, the Max winding
tap parameter tells the tap position number resulting in the maximum effective
number of winding turns.
The Min winding tap and Max winding tap parameters help the tap position
compensation algorithm know in which direction the compensation is being made.
This ensures also that if the current tap position information is corrupted for some
reason, the automatic tap changer position adaptation does not try to adapt to any
unrealistic position values.
GUID-075EC0C8-59AF-452F-B02D-0907E33D3481 V1 EN
Figure 330: Simplified presentation of the high voltage and medium voltage
windings with demonstration of the Max winding tap, Min winding tap
and Tap nominal parameters
Section 4
Protection functions
597