Meshed Network With Parallel Line - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
9.1.3.2
Transformer protection RET670 2.2 ANSI
Application manual
I
F
A
Z
~
A
IED
ANSI09000024 V1 EN-US
Figure 258: Fault current: I
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:
Is
=
Pickup
IBase
ANSIEQUATION1147 V1 EN-US

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 259, 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
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
on the healthy line (this applies for single-phase-to-ground and two-phase-to-ground
faults) is calculated.
Z
L
Fault
F
×
100
and I
fA
Section 9
Current protection
B
Z
~
B
ANSI09000024-1-en.vsd
mentioned previously. The
fB
259 will be with a fault
(Equation 417)
M12915-34 v7
)
M
517