ABB RED650 Applications Manual page 131

1MRK 505 393-UEN B
Line differential protection RED650 2.2 IEC
Application manual
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
If the denominator in equation
the 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-US
( )
×
( ) X m 0 Im
=
Im K 0
( )
2
+
Re B Im
EQUATION1428 V2 EN-US
Parallel line is out of service and earthed in both ends
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-earth faults.
Set the values of the corresponding zone (zero-sequence resistance and reactance)
equal to:
56 in section Parallel line in
58 is called B and Z0m is simplified to X0m, then
( )
B
( )
2
B
B
( )
2
B
Section 7
Impedance protection
GUID-98D11A72-C5BE-4C67-ADB5-95124C2AF987 v1
service.
(Equation 56)
(Equation 57)
(Equation 58)
(Equation 59)
(Equation 60)
GUID-345B36A6-B5FB-46DD-B5AE-81A1599FFC6E v1
125