Abstract: The field distribution and the dynamic balance process of the insulator surface under heavily icing condition are mainly related with the conductivity of ice water and the length of air gap,but are slightly affected by types or materials of insulators.A columnar model of insulator icing was established,and the dynamic balance equation of the icing process was established by three variables,which are length of the air gap,conductivity of ice water and melting efficiency based on the analysis of major factors affecting the ice growth;and the tests were carried out in the artificial climate room.The theoretic derivation and the experiment results indicated that the process of energized icing,which mainly affected by two factors,is a reversible process with the dynamic balance state existed.The critical conditions in different environments were obtained after implementing experimental study on the model;the result indicated that most of the Joule heat generated by various types of discharge during the energized icing process is used to maintain the arc combustion and the loss,only 15%-35% is used to melt the ice;and the heat for melting will be reduced with the increase of air-gap length.