ABB Relion 670 series - Setting of Zones for Parallel Line Application

8.3.3.5 Setting of zones for parallel line application
Parallel line in service – Setting of zone 1
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
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 115
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 (Equation 132)
X
0E
X
0
X
m0
+=
EQUATION554 V1 EN (Equation 133)
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 (Equation 134)
If the denominator in equation 134 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
(Equation 135)
Section 8 1MRK 506 369-UUS -
Impedance protection
244 Line distance protection REL670 2.2 ANSI
Application manual