Inspection of pin insulators in medium voltage distribution lines and outage reduction presents the results of a four-year field research study. The abstract and introduction are shown as in the following.

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.

Introduction:
In the first part of the present research [1] 6.728 insulators were analyzed at the High Voltage Laboratory of the Federal University of Itajubá – 1.934 of which were 15 kV class insulators and the remaining 4.794 25 kV class insulators. Considering transport issues, identification and other problems, 5.615 units were identified as being in test conditions, and of these, a further division was made of 1.443 15 kV class insulators and 4.172 25 kV class insulators.

Table 1 [1] presents the success and error indexes of the noise detector applied during the field inspections. It was observed that, in spite of the high success index for damaged insulators ranging from 90% to 70%, for noise levels between 0 and 10 dB, no similar correlation with respect to the success index for undamaged insulators was obtained, which, at its best, reached 40%. One possible source for this mismatch was the influence of the weather conditions, which calls for further investigation.

This paper discusses the influence of the weather conditions on the results of the noise detection during the field inspection of porcelain pin insulators and the correlation of the laboratory results based on a two-year field campaign involving 4.781 insulators, of which 1.129 were 15 kV class insulators and the remaining 3.625 25 kV class insulators. Finally, some further discussion on the possibility of improving the efficiency of the present set of techniques is also addressed.

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