![]() (Right) Effects on electric field with corona ring installed. 2: (Left) Electric field surrounding three differently shaped insulators. Note how each different shape influences gradient and also the location of the most vulnerable sections of an insulator operating within a high E-field. Black, orange and yellow-colored areas show the highest gradients. 2 shows three different insulator configurations with resulting electrical fields. For example, sharp edges, corners, points, tight radii or other irregular objects within a region of high E-field all have the potential to initiate corona. Darkened areas between sheds are fault pathway to ground.įor corona activity to exist, a high electric field is needed in combination with how the shapes of energized components influence that field. ![]() 1: Rupture pattern on polymeric insulator. The same effect can also be observed during daytime using solar blind UV cameras. This ‘recombination’ event releases energy in the form of light photons and is the glow commonly observed on transmission lines during low light conditions. This generally occurs in the vicinity of conducting surfaces but sometimes also near insulating surfaces due to ionization processes in air involving transfer of electrons being ‘knocked out’ of orbit and recaptured by atoms. Corona is not detectable during infrared inspection and its potentially destructive impact is often not fully understood or appreciated.Ĭorona is an electrical discharge in the high electric field region of an insulator. Although both utilities had been conducting annual visual and infrared inspections to identify threats to reliability and, while effective in rooting out certain issues, failures were nonetheless still experienced on polymeric insulators due to suspected corona activity. In response, Brady was contracted to carry out a comprehensive inspection of this asset. These power suppliers share operation of a crucial transmission line that experienced insulator failures. This edited contribution to INMR by James Brady, a Certified Level III Infrared Thermographer, reported on findings from line inspections conducted on behalf of two Florida-based utilities.
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