Studies on polymeric insulators for transmission systems under natural aging conditions

This work summarizes the results obtained after the evaluation of the electric properties plus physical and chemical characteristics of seven samples of polymeric insulators (organic, EPDM type) under natural aging at 115 kV operation voltage. The seven samples were obtained, from one to seven years insulators in normal service, respectively. First, the samples were subjected to some tests to verify the electrical characteristics. After that, the same samples were subjected to the physical and chemical tests. The results of the tests (electrical and physical-chemical), show important differences between the first sample (only one year in service) and the last sample (seven years in service), also a family of curves indicating the loss of electrical properties vs years in service was obtained. With these curves, the rest of service life of the samples was estimated maintaining the same field conditions. The criteria used for these evaluations were based on the critical values considered for the analyzed variables.