Importance Short Circuit (Or) For Fault Analysis

IMPORTANCE SHORT CIRCUIT (OR) FOR FAULT ANALYSIS

Fault

A fault in a circuit is any failure which interferes with the normal flow of current. The faults are associated with abnormal change in current, voltage and frequency of the power system.

Faults occur in a power system

The faults occur in a power system due to

(i). Insulation failure of equipment

(ii). Flashover of lines initiated by a lighting stroke

(iii). Due to permanent damage to conductors and towers or due to accidental faulty operations.

Various types of faults

(i) Series fault or open circuit fault

One open conductor fault

Two open conductor fault

(ii) Shunt fault or short circuit fault. Symmetrical fault or balanced fault

§ Three phase fault

Unsymmetrical fault or unbalanced fault

§ Line to ground (L-G) fault

§ Line to Line (L-L) fault

§ Double line to ground (L-L-G) fault

Relative frequency of occurrence of various types of fault

Symmetrical fault or balanced three phase fault

This type of fault is defined as the simultaneous short circuit across all the three phases. It occurs infrequently, but it is the most severe type of fault encountered. Because the network is balanced, it is solved by per phase basis using Thevenins theorem or bus impedance matrix or KVL, KCL laws.