ABB REL650 - Meshed Network with Parallel Line

ANSI10000275-1-en.vsd
~ ~
Z
A
Z
B
Z
L
A B
I
F
Fault
IED
ANSI10000275 V1 EN
Figure 84: Fault current: I
F
The IED setting valuePickup 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 102)
7.2.3.2 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 85 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 85 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 (I
M
) seen from the IED on
the healthy line (this applies for single-phase-to-ground and two-phase-to-ground faults)
is calculated.
1MRK 506 334-UUS A Section 7
Current protection
177
Application manual