Question

The consequence of the short circuit fault is
A. Dangerously high currents.
B. Circuit resistance reducing to almost zero.
C. Excessive heating which may cause a fire.
D. All of the above.

Answer 1

When the current in the circuit system increases abruptly with a sudden decrease in the voltage, the short circuit is said to have occurred. The excessive heating caused by the short circuit results in fire or explosion. The low voltage creates harmful effects on the power supply.

Complete step by step solution:
A short circuit fault occurs when there is an insulation failure between the phase conductors or between the phase conductor and the earth or both.
A fault like a large current flow in a network occurs, then, a short circuit is said to have occurred. The causes of the short circuit are internal effects and external effects. In the case of internal effects – the breakdown of the transmission lines, the ageing of insulation, the inadequate design or the improper installation can be the reasons. In the case of external effects – insulation failure, overloading, excessive heating may cause mechanical damage.
The properties of the short circuit fault are over current, under voltage, zero power factor, lagging, increased speed and the decreased frequency. In simple words, the short circuit fault is a high current, under voltage, zero power factor lagging phenomenon.
$\therefore$The consequence of the short circuit fault are dangerously high currents, the circuit resistance reducing to almost zero and the excessive heating which may cause fire,
Thus, option (D) all of the above is correct.

Note: The fault like large current flow in a network occurs, then, a short circuit is said to have occurred, this results in almost zero resistance in the network along with the low voltage. The types of fault are symmetrical faults, unsymmetrical faults, winding fault and the open circuit of phases. The positive sequence currents are present in all the types of faults mentioned above, the negative sequence currents are present in all unsymmetrical faults and the zero sequence currents are present when the neutral of the system is grounded.