IEC05000151-en-2.vsd
IN
>
One- or two-phase-earth-fault
3I
0
IEC05000151 V2 EN-US
Figure 266: Step 1, second calculation. Remote busbar with, one line taken out
of service
The requirement is now according to Equation 462.
step1 0I 1.2 3I (remote busbar with one line out)³ ×
EQUATION1200 V3 EN-US (Equation 462)
A higher value of step 1 might be necessary if a big power transformer (Y0/D) at
remote bus bar is disconnected.
A special case occurs at double circuit lines, with mutual zero-sequence impedance
between the parallel lines, see Figure
267.
IN
>
One phase-to-earth fault
3I
0
IEC05000152-en-2.vsd
IEC05000152 V2 EN-US
Figure 267: Step 1, third calculation
In this case the residual current out on the line can be larger than in the case of
earth fault on the remote busbar.
1MRK 506 369-UEN B Section 9
Current protection
Line distance protection REL670 2.2 IEC 485
Application manual
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