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Section 8
Impedance protection
8.9.3.5
308
-
³
×
Z
1.2 Z2
Z
rev
rem
L
EQUATION2314 V1 EN-US
Where:
Z
is the protected line impedance
L
Z2
is zone 2 setting at remote end of protected line.
rem
In many applications it might be necessary to consider the enlarging factor due to
fault current infeed from adjacent lines in the reverse direction in order to obtain
certain sensitivity.
Setting of zones for parallel line application
Parallel line in service – Setting of zone 1
With reference to section
85% of protected line.
However, influence of mutual impedance has to be taken into account.
Parallel line in service – setting of zone 2
Overreaching zones (in general, zones 2 and 3) must overreach the protected circuit
in all cases. The greatest reduction of a reach occurs in cases when both parallel
circuits are in service with a single phase-to-earth fault located at the end of a
protected line. The equivalent zero sequence impedance circuit for this case is
equal to the one in figure
The components of the zero sequence impedance for the overreaching zones must
be equal to at least:
R
=
R
+
R
0E
0
m0
EQUATION553 V1 EN-US
X
X
X
=
+
0E
0
m0
EQUATION554 V1 EN-US
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:
Z
0
m
= -
K
0 1
×
+
+
2
Z
1
Z
0
R
f
EQUATION1426 V1 EN-US
"Parallel line
applications", the zone reach can be set to
113
in section
"Parallel line
1MRK 506 369-UEN B
(Equation 250)
GUID-F10BF2FF-7B0F-40B0-877B-081E1D5B067B v1
GUID-8EAD617A-D33B-453C-83FC-21E3CFC37CB1 v1
applications".
(Equation 251)
(Equation 252)
(Equation 253)
Line distance protection REL670 2.2 IEC
Application manual
SEMOD55087-50 v2
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