Different types of faults in power system

The faults in a power system could be classified as symmetrical or unsymmetrical faults:

·         Symmetrical faults:

They involve 3-phase short-circuit. Symmetrical faults are the least probable type of faults. Symmetrical faults represent the most severe type of faults i.e. maximum short-circuit current. Therefore the breaking (rupturing) capacity of circuit-breakers is determined by that type of fault.

·         Unsymmetrical faults:

Comprise the following types of faults:

i.      Line-to ground faults

This is the most common type of faults. It usually results from a flashover on the insulator string, thus electrically connecting the conductor to ground

ii.    Line-to-line fault

This usually results when conductors of different phases touch each other. This can happen as a result of swinging of over-head conductors by wind.

iii.   Double line-to ground fault

This is similar to line-to-tine fault, but also involves fault to earth.