ABB RELION 620 Series Technical Manual page 766

Section 9
Control functions
760
GUID-B31F78EB-3DAD-40EF-A74B-5833C7B8696A-ANSI V1 EN
Figure 389: Angle difference when power transformer is in sychrocheck zone
The vector group of the power transformer is defined with clock numbers, where the value
of the hour pointer defines the low-voltage-side phasor and the high-voltage-side phasor
is always fixed to the clock number 12, which is same as zero. The angle between clock
numbers is 30 degrees. When comparing phase angles, the V_BUS input is always the
reference. This means that when the Yd11 power transformer is used, the low-voltage-
side voltage phasor leads by 30 degrees or lags by 330 degrees the high-voltage-side
phasor. The rotation of the phasors is counterclockwise.
The generic rule is that a low-voltage-side phasor lags the high-voltage-side phasor by
clock number * 30º. This is called angle difference adjustment and can be set for
SECRSYN with the Phase shift setting.
52
52
1MAC504801-IB E
620 series ANSI
Technical Manual