Meshed Network With Parallel Line - ABB RET650 Applications Manual

Section 7
Current protection
7.1.3.2
104
The minimum primary setting (Is) for the instantaneous phase overcurrent
protection is then:
³ ×
I 1.3 I
s min
EQUATION79 V3 EN-US
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
in Figure 41.
I
F
A
Z
~ A
IED
IEC09000024 V1 EN-US
Figure 41: Fault current: I
Is
>>= ×
IP 100
IBase
EQUATION1147 V3 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 42,
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
previously. The maximal influence from the parallel line for the IED in Figure
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 ) on the healthy line (this applies for single-phase-to-earth and two-phase-to-
M
earth faults) is calculated.
B
Z
L
Fault
F
Transformer protection RET650 2.2 IEC
1MRK 504 169-UEN A
(Equation 15)
Z
~
B
IEC09000024-1-en.vsd
(Equation 16)
M12915-34 v7
and I mentioned
fA fB
42
Application manual
F