ABB Relion 670 series - Page 279

0 1
2
1
3
N Nm
K
Z Z
K
Z
=
-
-
IECEQUATION14019 V1 EN (Equation 179)
For case 1, the measured impedance can be calculated by the following expression:
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 (Equation 180)
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 (Equation 181)
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
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 (Equation 182)
Alternative 2: Different groups of setting parameters for different operating
conditions of a protected multi circuit line
Different group of setting parameters can be used for the three cases:
• Parallel line switched off and grounded at both ends
• Parallel line switched off and not grounded or grounded at only one end
• Both lines in service.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 273
Application manual