Case 2: Parallel line switched off and not earthed or earthed at one line end
ANSI13000256 V1 EN
Figure 132: Parallel line is out of service and not earthed
0 1
1
1
1
1
3
N
Z x Z
K
Z Z
Z
+
= ×
+
-
×
IECEQUATION14012 V1 EN (Equation 174)
Case 3: Both lines in service
0m
ANSI13000257-1-en.vsd
x
Ph-G
ANSI13000257 V1 EN
Figure 133: Class 1, parallel line in service
GUID-354B9143-D19E-4835-BCEA-737D7C5E02AA V1 EN (Equation 175)
Some observations from above equations for case 1, 2, and 3
In case 1, the lowest impedance is measured, that is, the highest reach occurs due to the
parallel connection of the zero-sequence systems of both lines.
In case 3, the highest impedance is measured, which corresponds to the shortest reach.
Section 8 1MRK 506 369-UUS -
Impedance protection
270 Line distance protection REL670 2.2 ANSI
Application manual
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