ABB Relion 650 Series Technical Manual page 86

Section 5
Impedance protection
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 2.
=
Z
app
I _ A
EQUATION1546 V1 EN-US
Where:
V_A, I_A and IN
KN is defined as:
Z0 Z1
=
KN
×
3 Z1
EQUATION-2105 V1 EN-US
=
Z 0 R
EQUATION2106 V1 EN-US
=
Z 1 R 1
EQUATION2107 V1 EN-US
Where
R0
X0
R1
X1
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
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.
The directional evaluations are performed simultaneously in both forward and reverse directions,
and in all six fault loops. Positive sequence voltage and a phase locked positive sequence memory
voltage are used as a reference. This ensures unlimited directional sensitivity for faults close to
the IED point.
5.1.6.5 Simplified logic diagrams
80
V _ A
+ ×
I KN
N
are the phase voltage, phase current and residual current present to the IED
-
+
0 jX 0
+
jX 1
is the resistive zero sequence reach
is the reactive zero sequence reach
is the resistive positive sequence reach
is the reactive positive sequence reach
2
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is only valid for radial feeder application without load. When load
1MRK 506 326-UUS B
(Equation 2)
M13841-35 v2
Line distance protection REL650
Technical manual