Accelerated Multi Stress Aging and Life Estimation of Polymeric Insulators

Ceramic insulating materials are widely used for HV and EHV applications and were used for many decades. However, these materials response in a polluted environment and lack of hydrophobicity, high maintenance cost, etc., make them vulnerable. From the past decade, polymeric insulators evolved as the best replacement of these traditional materials. However, improvement in long term performance, service life and their aging behavior under different stresses in the field is still a challenging task for researchers. The impact of the environment on the performance of these insulators may vary depending on the severity of environment which necessitates, the proper investigation of performance for different environmental conditions, specifically for the regions having polluted environment. To understand the aging behavior and effects of different stresses on polymeric insulators, various aging techniques are applied worldwide. A lot of research is going on the natural as well as multi stress aging of polymeric insulators. Multi stress accelerated aging is an attractive technique used to simulate the effects of actual field environment and to analyze the long term service performance in a quite short time span. In this paper, the results of 10,000 hours of the aging test under accelerated multi stresses of the polymeric insulators are presented. Silicon rubber (SiR) is chosen from thermoset type and thermoplastic elastomeric (TPE) is chosen from the thermoplastic group. These insulators were applied multi stresses in accelerated weather chamber to be aged. The seasons (summer/winter) and time (day/night) are simulated for the weather cycles. The environmental region of Hattar, Pakistan, was simulated for designing the weather cycles which is an industrial area having high pollution index. The environmental stresses include heat, UV-A, acid rain and salt fog. The insulators selected for aging in this study are known as 10 kV distribution class insulators. The electrical analysis is based on leakage current and physical analysis are discoloration & classification of hydrophobicity, while material analysis technique considered here is Fourier Transform Infrared Spectroscopy (FTIR). This study showed that the TPE insulator lost its hydrophobicity initially with aging while SiR showed better hydrophobicity. Both TPE and SiR showed better leakage current suppression under the simulated environment of Hattar. Investigation of SiR and TPE insulators performance for the long term in the polluted industrial zone and their comparison under the same stresses condition with each other are the two main objectives of the study. Results revealed that both of the insulators are appropriate for the environment.