ABB Relion REQ650, Руководство по применению

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The IED setting value IP>> is given in percentage of the primary base current value,
IBase . The value for IP>> is given from this formula:
100
Is
IP
IBase
>>= ×
EQUATION1147 V3 EN
(Equation 11)
6.2.3.2 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
45 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 45 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-earth and two-phase-to-earth
faults) is calculated.
IEC10000278-1-en.vsd
~ ~
Z
A
Z
B
Z
L1
A B
I
M
Fault
IED
Z
L2
M
C
Line 1
Line 2
IEC10000278 V1 EN
Figure 45: Two parallel lines Influence form parallel line to the through fault
current: I
M
The minimum theoretical current (I
min
) for the overcurrent protection function will be:
Imin MAX I
fA
I
fB
I
M
, ,
( )
³
EQUATION82 V1 EN
(Equation 12)
1MRK 505 291-UEN A
Section 6
Current protection
93
Application manual