IEC09000025-1-en.vsd
~ ~
Z
A
Z
B
Z
L1
A B
I
M
Fault
IED
Z
L2
M
C
Line 1
Line 2
IEC09000025 V1 EN
Figure 58: Two parallel lines. Influence from parallel line to the through fault
current: I
M
The minimum theoretical current setting (Imin) will in this case be:
I m in M A X I
fA
I
fB
I
M
, ,( )³
EQUATION287 V1 EN (Equation 27)
Where:
I
fA
and I
fB
have been described for the single line case.
Considering the safety margins mentioned previously, the minimum setting (Is) is:
EQUATION288 V2 EN (Equation 28)
Transformer inrush current shall be considered.
The setting of the protection is set as a percentage of the base current (IBase).
Operation: set the protection to On or Off.
IN>>: Set operate current in % of IBase. IBase is a global parameter valid for all
functions in the IED.
6.6 Four step residual overcurrent protection, zero,
negative sequence direction EF4PTOC
1MRK 505 291-UEN A Section 6
Current protection
115
Application manual
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