Inspection of pin insulators in medium voltage distribution lines and outage reduction

This paper presents the results of a four-year field research study involving the inspection of porcelain pin insulators in medium voltage networks aiming at defining their operational condition when installed in medium voltage distribution lines. The initial part of this research [1], performed during the first two years, considered a preliminary rough inspection using electromagnetic noise detectors and detailed final inspection using ultrasonic noises detectors. During the discussion of the research results, the need for clarifying the influence of the weather conditions on the effectiveness of the applied set of techniques was clearly detected. Therefore, the temperature, the wind speed and the relative humidity of the air were also recorded during the last part of the present research and included in a data base together with the main insulator data. Throughout these 4 years, once a single noise-emitting insulator was detected, all insulators installed in the inspected pole were removed and substituted by equivalent post insulators. These insulators were further classified, tested and a comparison of field and laboratory results was carried out to check the influence of the weather conditions on the noise level, defined by the detectors, which determines the boundary limit between damaged & undamaged insulators. The laboratory tests were carried out at the High-Voltage Laboratory of the Federal University of Itajubá.