ABB RED650 - Page 601

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-US
Figure 294: Fault on transmission line fed from both ends
From figure 294 it is evident that:
U
A
I
A
p Z
L
I
F
R
F
×+× ×=
EQUATION95 V1 EN-US (Equation 78)
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-US (Equation 79)
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-US (Equation 80)
Thus, the general fault location equation for a single line is:
1MRK 505 394-UEN A Section 15
Monitoring
Line differential protection RED650 2.2 IEC 595
Technical manual