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2.8 Broken Conductor Protection
The unbalance condition caused by an open circuited conductor is detected by the broken
conductor protection. An unbalance threshold with programmable definite time delay is provided.
Figure 2.8.1.1 shows the sequence network connection diagram in the case of a single-phase series
fault assuming that the positive, negative and zero sequence impedance of the left and right side
system of the fault location is in the ratio of k
E
E
1A
Positive phase sequence
Negative phase sequence
Zero phase sequence
E
1A
Positive phase sequence current I
current I
at fault location in an single-phase series fault are given by:
0F
1A
k
1
k
Z
1
1
k
Z
2
2
k
Z
I
0
0
I
1F
k
Z
1
1
Z
1
E
1A
Figure 2.8.1.1 Equivalent Circuit for a Single-phase Series Fault
, negative phase sequence current I
1F
to (1 – k
), k
1
1
2
Single-phase series fault
I
I
1F
1F
I
I
2F
2F
I
0F
0F
k
Z
(1-k
)Z
2
2
2
2
K
Z
(1-k
)Z
0
0
0
0
I
Z
1F
2
Z
0
⎯ 39 ⎯
6 F 2 S 0 8 2 8
to (1 – k
) and k
to (1 – k
2
0
E
1B
1– k
1
(1-k
)Z
1
1
E
(1-k
)Z
2
2
(1-k
)Z
0
0
I
1F
(1-k
)Z
1
1
E
E
1B
and zero phase sequence
2F
).
0
1B
1B
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