ABB RET670 Applications Manual page 307

1MRK504116-UUS C
Application manual
Parallel line in service – Setting of zone1
With reference to section
of protected line.
Parallel line in service – setting of zone2
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 131 in section "Parallel line
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
X = X + X
0E 0 m0
EQUATION554 V1 EN
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
If the denominator in equation
real and imaginary part of the reach reduction factor for the overreaching zones can be
written as:
( )
×
( ) X m 0 Re
= -
Re K 0 1
( )
2
+
Re B Im
EQUATION1427 V2 EN
( )
×
X m 0 Im
( )
=
Im K 0
( )
2
+
Re B Im
EQUATION1428 V2 EN
"Parallel line applications", the zone reach can be set to 85%
applications".
222 is called B and Z0m is simplified to X0m, then the
B
( )
2
B
B
( )
2
B
Section 3
IED application
(Equation 220)
(Equation 221)
(Equation 222)
(Equation 223)
(Equation 224)
301