Electrical arc, sometimes referred to as plasma, what is it?
Electrical insulators, when subjected to a high enough voltage, undergo an electrical breakdown. When Electrical Breakdown occurs the electric current starts flowing through the insulator and what was the insulator then becomes an electricity conducting substance after an electrical breakdown.
In other words, Voltaic arc or plasma is the electrical discharge which occurs in the insulating substance during an electrical breakdown, and this happens at a specific voltage and specific conditions in an insulator.
The electrical spark can take place in an electrical insulator ( be it plastic, SF6, mineral oil, and even air or a vacuum). A dramatic electrical arc, with which we are all familiar with, is lightening, where the insulator is the air.
This natural phenomenon of arcing or sparking was first scientifically described by Sir Humphry Davy, in an 1801 paper published in William Nicholson’s Journal of Natural Philosophy, Chemistry, and the Arts.