The role of solid particles in prebreakdown phenomena in transformer oil

The prebreakdown and breakdown phenomena in liquid dielectrics subjected to high electric field have been the subjects of study since the beginning of this century. Unfortunately not enough progress has been made in formulating the phenomena leading to breakdown. There are two aspects of the problem of the prebreakdown phenomena in transformer oil. One is theoretical and is more difficult due to the complexity of the molecular structure of the oil. The other, a practical one, is the existence of various kinds of impurities even in purified oil. While very little has so far been achieved towards a theoretical solution of the problem, recent investigations are directed more towards the practical side. Increase in the dielectric strength of insulating oil with increased purity is now an established fact. Understanding the relative effects of various kinds of impurities should, therefore, lead to improved methods of purifying mineral oil for insulation purposes. [Continues.]