ABB RELION REX640 Technical Manual page 345

1MRS759142 C
REX640
Technical Manual
Faulted Used fault Used
phases current polarizing
voltage
A - B I - I U
A B 1
B - C I - I U
B C 1
C - A I - I U
C A 1
I U
A 1
U
A
I
I
B
C
U
C
A
GUID-DE5E5FFD-D45D-4501-8AD3-07C15B3522C8 V1 EN
Figure 192: 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.
Angle difference
ANGLE A U
_ ( )
ϕ
= −
1
GUID-62AD692C-5FA8-4A0D-9C04-63CBA54687F0 V1 EN
ANGLE B U
_ ( )
ϕ
= −
1
GUID-C1B47B56-1D3C-41C7-80BE-C1AF407D745E V1 EN
ANGLE C U
_ ( )
ϕ
= −
1
GUID-FC20AE2D-0E93-40DC-A013-9635CA70540A V1 EN
I
C
U
C
U
B
Section 4
Protection functions
I I
( ) 30 o
ϕ ϕ
− − +
A B RCA
(Equation 24)
I I
( ) 90 o
ϕ ϕ
− − −
B C RCA
(Equation 25)
I I
( ) 150 o
ϕ ϕ
− − +
C A RCA
(Equation 26)
U
A
U
1
-90°
I
A
I - I
B c
-I
C
I
B
U
B
B
1
339