IEC05000151-en-2.vsd
IN
>
One- or two-phase-earth-fault
3I
0
IEC05000151 V2 EN-US
Figure 86: Step 1, second calculation. Remote busbar with, one line taken out
of service
The requirement is now according to Equation 114.
step1 0I 1.2 3I (remote busbar with one line out)³ ×
EQUATION1200 V3 EN-US (Equation 114)
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
87.
IN
>
One phase-to-earth fault
3I
0
IEC05000152-en-2.vsd
IEC05000152 V2 EN-US
Figure 87: 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 505 393-UEN B Section 8
Current protection
Line differential protection RED650 2.2 IEC 177
Application manual
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