ABB RET670 - Page 405

ANSI09000024-1-en.vsd
~ ~
Z
A
Z
B
Z
L
A B
I
F
Fault
IED
ANSI09000024 V1 EN
Figure 181: 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 (Equation 336)
Meshed network with parallel line
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 182 where the
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
182 will be with a fault
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.
1MRK504116-UUS C Section 3
IED application
399
Application manual