Study of pin-type polymeric electric insulators: manufacturing process, tomographic analyses, and electrical and mechanical tests

Unlike other countries, pin-type porcelain insulators are still considered traditional in Brazil and are applied on a large scale in electric power distribution lines, in a predominantly aerial type configuration. Despite their low and therefore competitive cost, these insulators have undergone non-programmed shutdowns caused by defects in the dielectric material. A description is given herein not only of the manufacturing process of pin-type polymeric insulators, but also of computerized tomography-based analyses of these insulators to verify the homogeneity of the dielectric material's composition, as well as the results of alternating electric current tests and mechanical flexure tests before and after accelerated aging. This paper reports on a preliminary study, presenting and discussing pin-type polymeric insulators manufactured with castor oil-based polyurethane resins and comparing them with porcelain insulators. The results revealed that the aged and nonaged electric insulators displayed the same electrical behavior under alternating electric current, while the aged insulators showed greater mechanical rigidity.