ABB REL650 series, Technical Manual

Page: 127 / 856

apparent impedances at phase-to-phase faults follow equation 23 (example for a phase A
to phase B fault).
=
V
A
- V
B
Z
app
I
A
- I
B
EQUATION1545 V1 EN
(Equation 23)
Here V and I represent the corresponding voltage and current phasors in the respective
phase Ln (n = 1, 2, 3)
The ground return compensation applies in a conventional manner to phase-to-ground
faults (example for a phase A to ground fault) according to equation
24 .
=
+ ×
app
N
V _ A
Z
I _ A I KN
EQUATION1546 V1 EN
(Equation 24)
Where:
V_A, I_A and IN are the phase voltage, phase current and residual current present to the IED
KN is defined as:
Z0 Z1
KN
3 Z1
-
=
×
EQUATION-2105 V1 EN
0 0 0 Z R jX
= +
EQUATION2106 V1 EN
1 1 1 Z R jX
= +
EQUATION2107 V1 EN
Where
R0
is the resistive zero sequence reach
X0 is the reactive zero sequence reach
R1 is the resistive positive sequence reach
X1 is the reactive positive sequence reach
Here IN is a phasor of the residual current in IED point. This results in the same reach
along the line for all types of faults.
1MRK 506 335-UUS A
Section 6
Impedance protection
121
Technical manual