Question

Possible faults may occur on a transmission line are

1. 3-phase fault

2. L-L-G fault

3. L-L fault

4. L-G fault

The decreasing order of severity of the faults from the stability point of view is:
1. 1-2-3-4
2. 1-4-3-2
3. 1-3-2-4
4. 1-3-4-2

Answer 1

Correct Answer - Option 1 : 1-2-3-4

The different type of faults in power systems are:

• Single line to ground fault (LG)
• Line to line fault (LL)
• Double line to ground fault (LLG)
• Three-phase faults (LLL or LLLG)

 

Frequency of occurrence:

• Among the given faults, LG or line to ground fault is most common and occurs frequently.
• The order of frequency of occurrence is given below.

LG > LL > LLG > LLL

 

Severity of faults:

• Among the given faults, LLLG or 3 phase faults are most severe. LG or line to ground fault is least severe.
• Line to line fault is more severe than line to ground fault while double line to ground fault is one level severe than LL.
• The order of frequency of occurrence is given below.

LLL > LLG > LL > LG