ANSI09000024-1-en.vsd
~
~
Z
A
Z
B
Z
L
A
B
I
F
Fault
IED
ANSI09000024 V1 EN-US
Figure 258:
Fault current: I
F
The IED setting value
Pickup
is given in percentage of the primary base current value,
IBase
. The value for
Pickup
is given from this formula:
100
Is
Pickup
IBase
=
×
ANSIEQUATION1147 V1 EN-US
(Equation 417)
9.1.3.2
Meshed network with parallel line
M12915-34 v7
In case of parallel lines, the influence of the induced current from the parallel line to
the protected line has to be considered. One example is given in Figure
two lines are connected to the same busbars. In this case the influence of the induced
fault current from the faulty line (line 1) to the healthy line (line 2) is considered
together with the two through fault currents I
fA
and I
fB
mentioned previously. The
maximal influence from the parallel line for the IED in Figure
at the C point with the C breaker open.
A fault in C has to be applied, and then the maximum current seen from the IED (I
M
)
on the healthy line (this applies for single-phase-to-ground and two-phase-to-ground
faults) is calculated.
1MRK 504 163-UUS A
Section 9
Current protection
Transformer protection RET670 2.2 ANSI
517
Application manual
Summary of Contents for RELION RET670
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