ABB REL670 2.2 IEC - Page 262

2
0 1 0
1 0
1
1 (
1
)
3
N
m
Nm
Z x Z
K
Z Z Z
K
Z Z
+
= ×
+
-
-
×
IECEQUATION14017 V1 EN-US (Equation 177)
For case 2, the measured impedance can be calculated by the following expression:
2
0 1
1
1
1
1
3
N
Z x Z
K
Z Z
Z
+
= ×
+
-
×
IECEQUATION14016 V1 EN-US (Equation 178)
For both case 1 and 2, the overreach would be much higher. For case 3, the
function measures the correct impedance.
The normal influence of infeeds is to be added to these influences of the mutual
coupling for setting of remote backup zones.
Setting of zone 3
GUID-3F20E209-A29C-4D16-84AB-F0594DC10AC0 v1
The reach of zone 3 is affected as well, but when zone is normally set with
sufficient margin to always overreach the remote line end, K
N3
for zone 3 can be
set as for a single line, that is:
0 1
3
1
3
N
K
Z Z
Z
=
-
IECEQUATION14020 V1 EN-US (Equation 179)
Alternative 2: Different groups of setting parameters for different operating
conditions of a protected multi circuit line
GUID-DB67F163-289C-40C6-A850-074FFE61DEBC v2
Different group of setting parameters can be used for the three cases:
• Parallel line switched off and earthed at both ends
• Parallel line switched off and not earthed or earthed at only one end
• Both lines in service.
With this method of setting the zero sequence compensation factor K
N
can for zone
1 and zone 2 be even better adapted for the real system conditions.
The table describes earth-fault compensation settings to be adopted for different
groups.
Section 8 1MRK 506 369-UEN B
Impedance protection
256 Line distance protection REL670 2.2 IEC
Application manual