ABB RED615 Technical Manual page 196

Section 4
Protection functions
190
I U
A 1
U
A
I
I
B
C
U
C
A
GUID-1937EA60-4285-44A7-8A7D-52D7B66FC5A6 V3 EN
Figure 94: 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 rotating direction is counter-clockwise and defined as
"ABC". If the network rotating direction is reversed, meaning clockwise, that is,
"ACB", the equations for calculating the angle difference needs to be changed. The
network rotating direction is defined with a system parameter Phase rotation. The
change in the network rotating direction affects the phase-to-phase voltages
polarization method where the calculated angle difference needs to be rotated 180
degrees. Also, when the sequence components are used, which are, the positive
sequence voltage or negative sequence voltage components, the calculation of the
components are affected but the angle difference calculation remains the same.
When the phase-to-ground voltages are used as the polarizing method, the network
rotating direction change has no effect on the direction calculation.
The network rotating 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
1YHT530004D05 D
U
A
U
1
-90°
I
A
I - I
B c
-I
C
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B
1
Technical Manual
615 series