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"∗OB", "∗OJ", and "∗NC" and may display after the location result. These mean the followings:
∗OB: Fault point is over the boundary.
∗OJ: Fault point is over the junction in three-terminal line application.
∗NC: Fault calculation has not converged.
In case of a fault such as a fault duration time is too short, the fault location is not displayed and the
"---" marked is displayed.
2.17.4 Distance to Fault Calculation
2.17.4.1 Fault location using the local and remote end data
Calculation Principle
In the case of a two-terminal line as shown in Figure 2.17.4.1, the relationship between the
voltages at the local and remote terminals and the voltage at the fault point are expressed by
Equations (1) and (2).
Terminal A
V A - χ Z I A = V f
V B - (1 - χ )Z I B = V f
where,
V A = voltage at terminal A
I A
= current at terminal A
V B = voltage at terminal B
I B
= current at terminal B
χ
= distance from terminal A to fault point as a ratio to line length
V f
= voltage at fault point
Z
= line impedance
The distance χ is given by Equation (3) by eliminating V f ,
χ = (V A - V B + ZI B ) /Z(I A + I B ) (3)
As (I A + I B ) is equal to differential current Id, χ is calculated with the differential current
obtained as follows:
χ = (V A - V B + ZI B ) /ZI d
The distance calculation principle mentioned above can be applied to three-terminal lines. But in
V A
I A
χ
Figure 2.17.4.1 Two-terminal Model
150
Fault
V f
Z
1 − χ
(1)
(2)
(4)
6 F 2 S 0 8 5 0
Terminal B
V B
I B
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