ABB Relion 670 series, Technical Manual

Page: 195 / 1432

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 36 .
=
+ ×
app
N
V _ A
Z
I _ A I KN
EQUATION1546 V1 EN-US
(Equation 36)
Where:
V_A, I_A and IN are the phase voltage, phase current and residual current present to the IED
KN
is defined as:
0 1
3 1
Z Z
KN
Z
-
=
×
EQUATION-2105 V2 EN-US
0 0 0 Z R jX
= +
EQUATION2106 V2 EN-US
1 1 1 Z R jX
= +
EQUATION2107 V2 EN-US
Where
R0 is setting of the resistive zero sequence reach
X0 is setting of the reactive zero sequence reach
R1 is setting of the resistive positive sequence reach
X1 is setting of 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.
The apparent impedance is considered as an impedance loop with resistance R and reactance X.
The formula given in equation 36 is only valid for radial feeder application without load. When load
is considered in the case of single phase-to-ground fault, conventional distance protection might
overreach at exporting end and underreach at importing end. The IED has an adaptive load
compensation which increases the security in such applications.
Measuring elements receive current and voltage information from the A/D converter. The check
sums are calculated and compared, and the information is distributed into memory locations. For
each of the six supervised fault loops, sampled values of voltage ( V), current (I), and changes in
1MRK 502 066-UUS B Section 7
Impedance protection
189
Technical manual