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From symmetrical components, it is possible to derive the impedance Z at the IED
point for normal lines without mutual coupling according to equation
ph
ph
0
1
ph
N
ph
0
1
0
V
V
Z
Z
I
3
K
I
3I
3 Z
I
Z
=
=
-
+
×
+
×
×
EQUATION1275 V3 EN-US
(Equation 35)
Where:
Vph
is phase-to-ground voltage at the IED point
Iph
is phase current in the faulty phase
3I0
is ground-fault current
Z1
is positive sequence impedance
Z0
is zero sequence impedance
Z0m
A
B
21
21
en05000221_ansi.vsd
FAULT
ANSI05000221 V1 EN-US
Figure 72:
Class 1, parallel line in service
The equivalent circuit of the lines can be simplified, as shown in figure
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
197
Application manual
Summary of Contents for RELION RET670
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