Cause of Electrical Short Circuit Fires?

More details, please.

Very simplistically, electricity flows in a circuit and is limited by various resistances that prevent this flow from exceeding some specified safe current. When these resistances are removed or reduced the current will increase.

In electrical terms, when the circuit resistance and/or impedance is decreased, such as during a short circuit, the current can rise dramatically. This contributes to I-squared heating, meaning that the power increases as the square of the current through a resistive component. This heating can cause the component to flash and ignite adjacent combustible materials.

In most cases, a complete short circuit will blow a mains fuse, but sometimes it's a situation where there is really just an overload and the current rises, but not sufficiently to blow the fuse, that a circuit can just simmer and overheat to the point of igniting somthing.

There are numerous causes of electrical fires, but the best way to prevent them is to:

1 - use approved electrical equipment ONLY,

2 - leave all the infrastructure wiring to qualified electricians,

3 - ALWAYS use the proper fuses in the panel, and

4 - maintain all equipment in proper working order, repair or replace when necessary, and don't misuse it.

While this won't eliminate all of the fires, it will eliminate 99%. Nowdays, most electrical fires can be attributed to neglect or misuse of equipment.

Thanks for the detailed response.

Would like to advise if this issue has any connection to the faulty earth pit.

Possibly, but I'd suggest it would have more to do with the circuit itself. However, a faulty earth pit may contribute to shock hazards.

Electrical Earthing and Circuit Protective Devices

Electrical Earthing and Circuit Protective Devices Reasons For Earthing

There are four basic reasons for Earthing an electrical system:

REDUCTION OF SHOCK HAZARD

An earthed chassis will provide a low impedance path to ground for any active voltage that appears on the case or metalwork.

SAFE DISCONNECTION OF SUPPLY

If the exposed metalwork of an appliance were connected by a fault condition to an active conductor, the active current path needs to be able to flow to ground via a low impedance path so an excessive current will flow that will cause a protective device such as a fuse or circuit breaker to open circuit, thus prenting an electric shock situation.

MINIMISE THE DANGER OF FIRE HAZARD

The earth wire should always be in good contact with all metal parts of any appliance the user may touch. Should the equipment become faulty by the active wire touching the case, then current will rush to earth, smoke will rise from the equipment, and if the current is very high the fuse in the active line will blow, disconnecting mains power from the faulty appliance. Without the earth wire, this fault would go undetected, allowing high current to flow through the patient whenever the patient formed a circuit to ground. Standards limiting current in any circuit are vital to prevent excessive heating of the power supply wires leading to fires.

VOLTAGE STABILITY

Neutral earthing : Star point of Wye connected transformers and alternator windings are earthed primarily to provide voltage stability to system on account of imbalance in loading resulting in neutral current flow. Neutral point allows vector sum of three phase currents displaced at 120 degrees nullifying it to zero. Secondary purpose served is detection of earth faults or earth leakages and allow the protective gear to operate in desired time.

In the view of high harmonic contents found in modern facilities, the zero sequence or triplen harmonic currents overload the neutrals if not adequately sized. This is because these are in phase and hence do not cancel out at neutral point. So neutrals are required to be sized equal to or sometimes double the size of line conductors to carry "algebraic sum" of triplen components in the lines.

Neutral earthing for applicable to low voltage distribution systems upto 1000 V ac comprise of solid earthing with no intentional resistance connected in the path.

Please see following links to understand What is earthing in electrical system

http://picearthingtech.com/

Regards

Raju