ABB REL670 2.2 IEC - Page 308

A
B
C
IEC09000252_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0
-
Z
0m
IEC09000252 V1 EN-US
Figure 153: Equivalent zero sequence impedance circuit for the double-circuit
line that operates with one circuit disconnected and earthed at both
ends.
Here the equivalent zero sequence impedance is equal to Z
0
-Z
0
m in parallel with
(Z
0
-Z
0m
)/Z
0
-Z
0m
+Z
0m
which is equal to equation 243.
2 2
0
0
om
E
Z Z
Z
Z
-
=
EQUATION2002 V4 EN-US (Equation 243)
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
0m
equals to zero. They consider only the zero
sequence, mutual reactance X
0m
. Calculate the equivalent X
0E
and R
0E
zero
sequence parameters according to equation 244 and equation 245 for each
particular line section and use them for calculating the reach for the underreaching
zone.
R R
X
R X
E
m
0 0
0
2
0
2
0
2
1= ⋅ +
+








DOCUMENT11520-IMG3502 V2 EN-US (Equation 244)
X X
X
R X
E
m
0 0
0
2
0
2
0
2
1= ⋅ −
+








DOCUMENT11520-IMG3503 V2 EN-US (Equation 245)
Section 8 1MRK 506 369-UEN B
Impedance protection
302 Line distance protection REL670 2.2 IEC
Application manual