ABB REC650 ANSI - Page 517

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 225: Fault on transmission line fed from both ends
From figure 225 it is evident that:
= × × + ×
A A L F F
V I p Z I R
EQUATION1595 V1 EN (Equation 61)
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:
I
F
I
FA
D
A
--------
=
EQUATION96 V1 EN (Equation 62)
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:
1MRK 511 287-UUS A Section 12
Monitoring
511
Technical manual