- The simplest and the most commonly found dielectrics are gases.
- Most of the electrical apparatus use air as the insulating medium
- Such gases are nitrogen, CO2, CCl2F2, SF6
- When the applied voltage is low, small currents flow between the electrodes and the insulation retains its electrical properties.
- When the applied voltage is large, the current flowing through the insulation increases very sharply, and an electrical breakdown occurs
- The maximum voltage applied to the insulation at the moment of break down is called break down voltage.
- The break down in a gas, called spark break down is the transition of a non- sustaining discharge to Self-sustaining discharge.
Two Types of Electrical Discharges in Gases
- Non-sustaining discharges
- Self-sustaining discharges