IEC09000023-1-en.vsd
~
~
Z
A
Z
B
Z
L
A
B
IED
I
fA
Fault
IEC09000023 V1 EN-US
Figure 53:
Through fault current from B to A: I
fA
The function shall not operate for any of the calculated currents to the protection.
The minimum theoretical current setting (Imin) will be:
Im
,
fA
fB
in
MAX I
I
EQUATION284 V2 EN-US
(Equation 38)
A safety margin of 5% for the maximum static inaccuracy and a safety margin of
5% for maximum possible transient overreach have to be introduced. An additional
20% is suggested due to inaccuracy of instrument transformers under transient
conditions and inaccuracy in the system data.
The minimum primary current setting (Is) is:
I
s
= 1.3 ×
I
min
EQUATION285 V3 EN-US
(Equation 39)
In case of parallel lines with zero sequence mutual coupling a fault on the parallel
line, as shown in Figure
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-US
Figure 54:
Two parallel lines. Influence from parallel line to the through fault
current: I
M
Section 8
1MRK 506 375-UEN A
Current protection
168
Railway application RER670 2.2 IEC
Application manual
Summary of Contents for RELION RER670
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