ABB RELION 620 Series Technical Manual page 433

1MAC504801-IB E
620 series ANSI
Technical Manual
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 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 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 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 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.
Max winding tap
Tap nominal
Min winding tap
GUID-8ABE1159-7804-4369-BC04-E92E5BD95164 V1 EN
Figure 195: Simplified presentation of the HV and LV windings in the case of 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 the tap position indication function 84T. When the quality of the
TAP_POS input value is not good, the position information in the TAP_POS input is not
used, but the last value with the good quality information is used instead. In addition, the
minimum sensitivity of the biased stage, set by the Low trip value setting, is automatically
desensitized with the total range of the tap position correction. The new acting low trip
value can be calculated.
Desensitized Lowtrip value Lowtrip value ABS Max winding tap Mi
=
GUID-1F37B0DD-DA91-46EA-8E3D-4736AA1E20B0 V1 EN
Protection functions
(HV)
(
+ −
Section 4
(LV)
n n winding tap )× Step of tap
(Equation 45)
427