Improving results of thermographic inspections of electrical transmission and distribution lines

Inspecting compression splices on transmission and distribution lines has long been accomplished using infrared thermography but the results have too often been disappointing. There are instances of splices failing within months of infrared inspections. An understanding of the actual condition of the splices had been "masked" by one or more of the factors discussed in this paper. A number of factors are involved, including a poor understanding of the application of the technology; inadequate training of some service providers; environmental factors; low electrical loading; the resolution limitations of the inspection equipment; low emissivity of the components, and poor interpretation of the data. Too often the severity of the problems found has been underestimated and some bad fittings have simply not been located. In a deregulated environment, electric utilities will require more predictable reliability. In part, this will be accomplished through a much higher level of confidence in the assessment of the condition of compression fittings. This paper discusses the background for using thermography in the industry and the results that have been achieved in the past, as well as the use of resistance measurements to assess the condition of compression fittings. It also details steps that can be taken to improve the infrared results to provide for greater confidence in the interpretation of the data collected.