ABB REL650 series, Applications Manual, Page: 178 / 516

The minimum primary setting (Is) for the instantaneous phase overcurrent protection 3-
phase output is then:
min
1.3
s
I I
³ ×
EQUATION79 V3 EN
(Equation 95)
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
F
in figure 80 .
ANSI09000024-1-en.vsd
~ ~
Z
A
Z
B
Z
L
A B
I
F
Fault
IED
ANSI09000024 V1 EN
Figure 80: 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 96)
7.1.3.2 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
81 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 81 will be with a fault at the C point with the C breaker
open.
Section 7
1MRK 506 334-UUS A
Current protection
172
Application manual