ABB REC650 - Page 482

Z
A
pZ
L
A
U
A
I
F
R
F
(1-p).Z
L
B
Z
B
F
L
I
B
I
A
xx01000171.vsd
IEC01000171 V1 EN
Figure 225: Fault on transmission line fed from both ends
From figure 225 it is evident that:
U
A
I
A
p Z
L
I
F
R
F
×+× ×=
EQUATION95 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:
D
A
1 p–( ) Z×
L
Z
B
+
Z
A
Z
L
Z
B
+ +
-----------------------------------------
=
EQUATION97 V1 EN (Equation 63)
Section 12 1MRK 511 287-UEN A
Monitoring
476
Technical manual