Check the reduction of a reach for the overreaching zones due to the effect of the zero
sequence mutual coupling. The reach is reduced for a factor:
0
0 1
2 1
0
m
f
Z
K
Z
Z
R
= -
×
+
+
EQUATION1426 V1 EN-US
(Equation 180)
If the denominator in equation
is called B and Z0m is simplified to X0m, then the
real and imaginary part of the reach reduction factor for the overreaching zones can be
written as:
( )
( )
( )
( )
2
2
0
Re
Re
0
1
Re
Im
X m
B
K
B
B
×
= -
+
EQUATION1427 V2 EN-US
(Equation 181)
( )
( )
( )
( )
2
2
0
Im
Im
0
Re
Im
X m
B
K
B
B
×
=
+
EQUATION1428 V2 EN-US
(Equation 182)
Parallel line is out of service and grounded in both ends
SEMOD154704-69 v3
Apply the same measures as in the case with a single set of setting parameters. This
means that an underreaching zone must not overreach the end of a protected circuit for
the single phase-to-ground faults. Set the values of the corresponding zone (zero-
sequence resistance and reactance) equal to:
R
0E
R
0
1
X
m0
2
R
0
2
X
0
2
+
--------------------------
+
è
ø
ç
÷
æ
ö
×
=
EQUATION561 V1 EN-US
(Equation 183)
X
0E
X
0
1
X
m0
2
R
0
2
X
0
2
+
--------------------------
–
è
ø
ç
÷
æ
ö
×
=
EQUATION562 V1 EN-US
(Equation 184)
8.5.3.6
Setting of reach in resistive direction
SEMOD154704-76 v1
Set the resistive reach independently for each zone, for phase-to-ground loop (
RIPE
)
measurement.
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
309
Application manual
Summary of Contents for RELION RET670
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