Mechanisms Responsible for Corona Formation & Breakdown in Non-Uniform Field at Power Frequency

Though efforts are made in the design to maintain the field as uniform as may be, in Engineering works quite often it happens that due to manufacturing difficulties, special limitations & many other factors, the non-uniformity of field creeps in. The peculiarity of the non-uniform field is the occurrence of corona prior to break-down. As corona is known to cause a considerable damage to the insulation system & break-down causes complete damage of the system, the high voltage Engineers face the troubles due to the occurrence of corona & break-down in the operation & maintenance of any high voltage equipment or system. As corona occurs only in non uniform field, the study of non-uniform field assumes importance both from corona & breakdown point of view. In the present discussion use is made of a needle-plane gap, since a needle-plane arrangement gives highly divergent field.

In the following discussions, efforts have been made to explain the mechanism responsible for corona formation in non-uniform field & also the consequences which lead to its break-down have been pointed out.