The influence of the Corona Current to the Ground and the Polarity Effect of small air gaps

The Corona Current in air gaps influences the values of the breakdown voltage of the air gaps greatly. This happens because the corona current changes the field distribution in the gap making it less inhomogeneous. Thus the value of the breakdown voltage increases and becomes bigger as the value of the corona current increases. A major result of this phenomenon is the appearance of the Polarity Effect. The Polarity Effect is a phenomenon occurring due to the alteration of the polarity of the applied voltage to the gaps. When the applied voltage is negative the value of the breakdown voltage is bigger and this happens because the corona current is considerably higher. A second important result of the Corona Current Effect is the inversion of the Ground Effect. The Ground Effect is the phenomenon that occurs due to the different way the gap is grounded and influences the distribution of the field in the gap, the corona onset voltage, as well as the breakdown voltage in small gaps. In longer air gaps, the Corona Effects become very intense and the influence of the Ground Effect to the breakdown voltage is overlapped. The principle of action-reaction is valid. “The corona current reacts against the action of the field to produce corona charges and makes the field less inhomogeneous”