- Few years ago, most of the electrical apparatus are used air as a insulating medium.
- Now a days, various gases are used for insulating medium such as nitrogen (N2), freon (CCl2F2) and sulphur hexafluoride (SF6).
- During testing when applied voltage is low, small currents flow between the conducting electrodes and the insulation keep its electrical properties.
- Whereas, if applied voltage is high, the large amount of current flowing through the insulation between electrodes and an electrical breakdown occurs.
- The maximum voltage applied to the insulation at the moment of breakdown occur is known as breakdown voltage.
- Two types of electrical discharge in gases :
- Non-sustaining discharge
- Self-sustaining discharge
- There are the various physical conditions of gases, like pressure, temperature, electrode field configuration, nature of electrode surfaces and the availibility of initial conducting particles are called the ionization processes.
