Arc flash

Arc flash is an accidental electrical explosion usually caused by a short circuit. It usually happens at higher-voltages (around 300 volts and above). It can cause the electrical conductors to melt creating an explosion of molten or even vaporized metal. Temperatures can be as high as 20000 degrees Celsius. Arc flash is one of the reasons it is so important to turn the power off before working on any high-voltage equipment.

Arc Flash Media

An electric arc between two nails
A 480 volt switchgear and distribution panel, requiring category-4 arc-flash protection.
A video describing the dangers of arc flashes and measures that can be taken to reduce risk to workers
Example of IED equipped with arc protection

This short article about science can be made longer. You can help Wikipedia by adding to it.