ABB RELION 650 Series Applications Manual page 117

1MRK 505 363-UEN A
=
Z
E
EQUATION2002 V4 EN-US
The influence on the distance measurement will be a considerable overreach, which must be
considered when calculating the settings. It is recommended to use a separate setting group
for this operation condition since it will reduce the reach considerably when the line is in
operation.
All expressions below are proposed for practical use. They assume the value of zero sequence,
mutual resistance R
X . Calculate the equivalent X
0m
and equation
underreaching zone.
R =
0 E
DOCUMENT11520-IMG3502 V2 EN-US
X =
0 E
DOCUMENT11520-IMG3503 V2 EN-US
Parallel line out of service and not earthed
A
Z<
IEC09000254 V1 EN-US
Figure 61: Parallel line is out of service and not earthed
When the parallel line is out of service and not earthed, the zero sequence on that line can only
flow through the line admittance to the earth. The line admittance is high which limits the
zero-sequence current on the parallel line to very low values. In practice, the equivalent zero-
sequence impedance circuit for faults at the remote bus bar can be simplified to the circuit
shown in figure
The line zero sequence mutual impedance does not influence the measurement of the distance
protection in a faulty circuit. This means that the reach of the underreaching distance
protection zone is reduced if, due to operating conditions, the equivalent zero sequence
impedance is set according to the conditions when the parallel system is out of operation and
earthed at both ends.
Application manual
2 2
-
Z Z
0 om
Z
0
equals to zero. They consider only the zero sequence, mutual reactance
0m
0E
48 for each particular line section and use them for calculating the reach for the
2
 
X
0 m
R ⋅  1 + 
0
 
2 2
R + X
 
0 0
2
 
X
0 m
X ⋅  1 − 
0
 
2 2
R + X
 
0 0
B
Z
0m
Z<
IEC09000254_1_en.vsd
61
and R zero sequence parameters according to equation
0E
Section 7
Impedance protection
(Equation 46)
47
(Equation 47)
(Equation 48)
GUID-949669D3-8B9F-4ECA-8F09-52A783A494E1 v2
111