Meshed Network With Parallel Line - ABB REL650 Applications Manual

Section 7
Current protection
7.1.3.2
172
The minimum primary setting (Is) for the instantaneous phase overcurrent protection 3-
phase output is then:
³ ×
I 1.3 I
s min
EQUATION79 V3 EN
The protection function can be used for the specific application only if this setting value
is equal to or less than the maximum fault current that the IED has to clear, I
I
F
A
Z
~ A
IED
ANSI09000024 V1 EN
Figure 80: 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

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
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
parallel line for the IED in figure
open.
Z
L
Fault
F
×
100
and I mentioned previously. The maximal influence from the
fB
81 will be with a fault at the C point with the C breaker
1MRK 506 334-UUS A
F
B
Z
B ~
ANSI09000024-1-en.vsd
81 where the two lines
Application manual
(Equation 95)
in figure 80.
(Equation 96)