ABB RELION RET670 - Setting of Zones for Parallel Line Application

8.3.3.5 Setting of zones for parallel line application
SEMOD55087-50 v2
Parallel line in service – Setting of zone 1
SEMOD55087-52 v3
With reference to section "Parallel line applications", the zone reach can be set to 85%
of the protected line.
However, influence of mutual impedance has to be taken into account.
Parallel line in service – setting of zone 2
SEMOD55087-55 v4
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-
ground 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
126 in section "Parallel line in service".
The components of the zero sequence impedance for the overreaching zones must be
equal to at least:
R
0E
R
0
R
m0
+=
EQUATION553 V1 EN-US (Equation 137)
X
0E
X
0
X
m0
+=
EQUATION554 V1 EN-US (Equation 138)
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 139)
If the denominator in equation 139 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 140)
Section 8 1MRK 504 163-UUS A
Impedance protection
278 Transformer protection RET670 2.2 ANSI
Application manual