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Outdoor Substation Arrestors

Infrared inspections of lightning arrestors are primarily qualitative in nature. As such, thermographers should compare similar arrestors to one another and note any that are inexplicably warm.

Properly functioning lightning arrestors should be uniform in temperature and close to ambient air temperature if they have not undergone recent solar loading. Individual arrestors should not have any pronounced hot spots across them.

Because arrestors usually have a glazed porcelain surface, infrared inspections are best accomplished using a short wave (3-5 micron) imager. Working on cloudy days or at night will help to eliminate solar loading. When performing your inspection, don’t forget to check grounding connections for hot spots as well.