Study on the field behavior at the contact point between a covered conductor and a dielectric solid

Abstract

We study the electric field behavior in a configuration of a cylindrical covered conductor lying on a dielectric solid, which is a simplified configuration of a space aerial cable (SAC) on a spacer. The SACs, which are a partially insulated cable, are used in Thailand by electric utilities to reduce space requirement for distribution lines and to prevent faults on the line by a contact with objects. However, after a period of use, the losses of cable insulation at the spacer position have been found, in particular for the SAC installed with porcelain spacers whose dielectric constant is much higher than that of the cable insulation. In this work, we apply an analytical method to the electric field calculation. The calculation results show that at the contact point between the covered conductor and the dielectric solid, the electric field is intensified with increasing the dielectric constant of the dielectric solid. As porcelain spacers are still needed for mechanical reasons, we investigate the field behavior in modified configurations in order to mitigate the field at the contact point. The modification includes (i) applying a thicker insulation layer to the covered conductor, (ii) inserting a HDPE sheet in between the covered conductor and the dielectric solid, and (iii) enclosing the covered conductor by a floating conductor. The changes in the electric field in each case are then discussed.