Z
A
pZ
L
A
I
F
(1-p).Z
L
B
Z
B
F
L
I
B
I
A
xx01000171_ansi.vsd
R
F
A
V
ANSI01000171 V1 EN
Figure 122: Fault on transmission line fed from both ends
From figure 122 it is evident that:
= × × + ×
A A L F F
V I p Z I R
EQUATION1595 V1 EN (Equation 58)
Where:
I
A
is the line current after the fault, that is, pre-fault current plus current change due to the fault,
I
F
is the fault current and
p
is a relative distance to the fault
The fault current is expressed in measurable quantities by:
EQUATION96 V1 EN (Equation 59)
Where:
I
FA
is the change in current at the point of measurement, IED A and
D
A
is a fault current-distribution factor, that is, the ratio between the fault current at line end A and
the total fault current.
For a single line, the value is equal to:
Section 12 1MRK 505 277-UUS C
Monitoring
304
Technical Manual
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