ABB REC650 Technical Manual page 482

Section 12
Monitoring
476
F
A
Z pZ
I
A
A
U
A
IEC01000171 V1 EN
Figure 225: Fault on transmission line fed from both ends
From figure 225 it is evident that:
× × ×
U I p Z I R
= +
A A L F F
EQUATION95 V1 EN
Where:
I is the line current after the fault, that is, pre-fault current plus current change due to the fault,
A
I is the fault current and
F
is a relative distance to the fault
p
The fault current is expressed in measurable quantities by:
I
F A
------- -
I =
F
D
A
EQUATION96 V1 EN
Where:
I is the change in current at the point of measurement, IED A and
FA
D is a fault current-distribution factor, that is, the ratio between the fault current at line end A and
A
the total fault current.
For a single line, the value is equal to:
( ) Z ×
1 p – + Z
L B
-----------------------------------------
D =
A
Z Z Z
+ +
A L B
EQUATION97 V1 EN
L
(1-p).Z
I
L L
B
I
F
R
F
1MRK 511 287-UEN A
B
Z
B
xx01000171.vsd
(Equation 61)
(Equation 62)
(Equation 63)
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