ABB Relion 670 series - Measuring principles

6.2.2.4 Measuring principles
Fault loop equations use the complex values of voltage, current, and changes in the
current. Apparent impedances are calculated and compared with the set limits. The
calculation of the apparent impedances at ph-ph faults follows equation
14 (example
for a phase A to phase B fault).
=
V
A
- V
B
Z
app
I
A
- I
B
EQUATION1545 V1 EN (Equation 14)
Here V and I represent the corresponding voltage and current phasors in the respective
phase.
The ground return compensation applies in a conventional manner to ph-g faults
(example for a phase A to ground fault) according to equation
15.
=
+ ×
app
N
V _ A
Z
I _ A I KN
EQUATION1546 V1 EN (Equation 15)
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 0Z R jX= +
EQUATION2106 V1 EN
1 1 1Z R jX= +
EQUATION2107 V1 EN
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
Section 6 1MRK505222-UUS C
Impedance protection
202
Technical reference manual