ABB RELION 620 Series Technical Manual page 304

Section 4
Protection functions
298
I U
A 1
U
A
I
I
B
C
U
C
A
GUID-1937EA60-4285-44A7-8A7D-52D7B66FC5A6 V3 EN
Figure 149: Phasors in a single-phase earth fault, phase A to ground, and a two-
phase short circuit, phases B-C, are short-circuited when the
polarizing quantity is the positive-sequence voltage U
Network rotation direction
Typically, the network rotatiion direction is counterclockwise and defined as "ABC".
If the network rotation direction is reversed, meaning clockwise, that is, "ACB", the
equations for calculating the angle difference need to be changed. The network
rotation direction is defined with a system parameter Phase rotation. The change in
the network rotation direction affects the polarization method of the phase-to-phase
voltages where the calculated angle difference needs to be rotated 180 degrees. Also,
when the sequence components are used, the calculation of the components is affected
but the angle difference calculation remains the same. The sequence components are
the positive-sequence voltage or negative-sequence voltage components. When the
phase-to-ground voltages are used as the polarizing method, the network rotation
direction change has no effect on the direction calculation.
The network rotation direction is set in the IED using the parameter in
the HMI menu: Configuration/System/Phase rotation. The default
parameter value is "ABC".
I
C
U
C
U
B
1MRS757644 F
U
A
U
1
-90°
I
A
I - I
B c
-I
C
I
B
U
B
B
1
Technical Manual
620 series