Effect of the interfacial pressure and electrode gap on the breakdown strength of various dielectric interfaces [in underground power cables]

Electrical breakdown at the interface of two dielectric surfaces is a major design consideration in underground power cable accessories. The authors´ previous studies have shown that the dielectric strength of greased and nongreased interfaces can be greatly affected by their surface conditions as well as their substrate material. These observations were made in both laboratory molded samples and real cable joints. The present paper deals with the effect of the interfacial pressure and electrode gap on the breakdown strength of various molded dielectric interfaces. Results showed that greased and nongreased interfaces each have a distinct behavior in both parameters examined. Finally, a plot of the breakdown voltage as a function of the product of pressure and gap was introduced and seems to give a more appropriate representation of both effects