Performance evaluation of 15 kV polymeric insulators for dead-end type applications on distribution systems

Results are reported of a research program to investigate the performance of polymeric insulators for 15 kV dead-end applications on distribution systems. The test program involved both new insulators from five different manufacturers and naturally aged insulators removed from service on the distribution system of Pennsylvania Power & Light. The test series to evaluate the new insulators included preconditioning treatments, salt fog and tracking wheel accelerated aging tests, electrical tests, and material and physical tests. The tests for the naturally aged insulators were mainly limited to the electrical tests and the material and physical tests. It is found that some of the polymeric insulators installed on the distribution system have limited remaining service life. The performance of the naturally aged insulators in the test program indicates that the electrical characteristics of the early production insulator has degraded from published data. These results substantiate concerns about insulator performance based on external appearance. The new insulators show marked improvement over the first generation of insulators provided sufficient filters are added to alleviate erosion and tracking problems. Based on the preconditioning and accelerated aging test results, a 30-year field life does not appear unreasonable