ABB Relion 670 series, Руководство по применению

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Parallel line out of service and not earthed
GUID-DF8B0C63-E6D1-4E11-A8CB-D0C8EAE10FF0 v1
Z
0m
A B
Z< Z<
IEC09000254_1_en.vsd
IEC09000254 V1 EN-US
Figure 208: 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 208
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.
A
B
C
IEC09000255_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0m
Z
0
-
IEC09000255 V1 EN-US
Figure 209: Equivalent zero-sequence impedance circuit for a double-circuit line with one
circuit disconnected and not earthed
The reduction of the reach is equal to equation 373 .
( )
( )
( )
2
1 0
0
1 0
0
1 0
1
2
3
1
1
2 3
2
3
E f
m
U
f
f
Z Z R
Z
K
Z Z Z R
Z Z R
× × + +
= = -
× × + +
× × + +
EQUATION1284 V1 EN-US
(Equation 373)
This means that the reach is reduced in reactive and resistive directions. If the real and
imaginary components of the constant A are equal to equation 374 and equation 375 .
Re( ) 0 (2 1 0 3 ) 0 ( 0 2 1) A R R R Rf X X X
= × × + + × - × + ×
EQUATION1285 V1 EN-US
(Equation 374)
0 1 0 1 0 1 0
Im( ) (2 3 ) (2 ) A X R R R R X X
= × × + + × + × × +
EQUATION1286 V1 EN-US
(Equation 375)
The real component of the KU factor is equal to equation 376 .
Section 7 1MRK 505 343-UEN B
Impedance protection
334
Application manual