Woodward HighPROTEC - Page 643

Protective Elements
Tap Changer:
The tap changer changes the transformer voltage ratio
k
Tap
.
k
Tap
=
V
LL,W1
(1+Tap Changer)
V
LL,W2
Principally, the following calculations need to be executed before calculating differential values and restraining
values of the transformer differential protection:
• Rotating the measured values of winding 2 to the reference winding 1 count-clockwise
with an angle of rotation number (0, 1, …..11) * 30 degrees;
• Adjustment of measured values for winding 2 with respect to CT ratio mismatch;
• Adjustment of measured values for winding 2 with respect to winding connection (y, d, z); and
• Adjustment of measured values for winding 1 and winding 2 according to neutral connection and ground
treatment (zero sequence current elimination).
643 MCDGV4 DOK-HB-MCDGV4-2E