Meshed Network With Parallel Line - ABB REG670 Applications Manual

Section 9
Current protection
9.1.3.2
322
The minimum primary setting (Is) for the instantaneous phase overcurrent protection
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
Figure 170.
I
F
A
Z
~ A
IED
IEC09000024 V1 EN
Figure 170: Fault current: I
Is
>>= ×
IP 100
IBase
EQUATION1147 V3 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 171, 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
maximal influence from the parallel line for the IED in Figure
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-earth
faults) is calculated.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
B
Z
L
Fault
F
and I
fA fB
1MRK 502 071-UEN -
(Equation 176)
Z
~
B
IEC09000024-1-en.vsd
(Equation 177)
mentioned previously. The
171 will be with a fault
Application manual
in
F
)
M