Toshiba GR200 Series - 2.19.1 Equivalent circuit for a one-phase series fault

6F2S1914 (0.49)
GRL200 (Soft 033 & 037)
- 286 -
2.19.1 Equivalent circuit for a one-phase series fault
Figure 2.19-1 shows the sequence diagram of the network connection when a single-phase
series fault occurs. We can represent the series fault by the positive sequence, negative
sequence and zero sequence impedances; the impedances are distributed to the left and right
as shown in the diagram of the primary circuit below. The ratio of the left to the right is
determined by the fault location such as k1:1-k1, k2:1-k2, and k0:1-k0.
Figure 2.19-1 Equivalent circuit for a single-phase fault
The series fault results in positive sequence current (I
1F
), negative sequence current (I
2F
)
and zero phase sequence current (I
0F
) in the single-phase. These are given by


 

 


(2.19-1)




 




(2.19-2)


 





 



(2.19-3)
where,
E
1A
, E
1B
: power source voltage
Z
1
: positive sequence impedance
Z
2
: negative sequence impedance
Z
0
: zero sequence impedance
Positive sequence
Series or open circuit fault
Zero sequence
k
2
Z
2
(1-k
2
)Z
2
k
0
Z
0
(1-k
0
)Z
0
E
1A
E
1B
I
1F
I
1F
I
2F
I
2F
I
0F
I
0F
Negative sequence
(1-k
1
)Z
1
k
1
Z
1
E
1B
E
1A
k
1
1– k1
E
1A
E
1B
I
1F
k
1
Z
1
k
2
Z
2
(1-k
2
)Z
2
K
0
Z
0
(1-k
0
)Z
0
E
1A
E
1B
I
1F
Z
1
Z
2
Z
0
(1-k
1
)Z
1