11 May 2016 Classification of electrical problems detected by infrared thermography using a risk assessment process
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For more than 40 years thermography has been used for electrical problem detection. In addition, since radiometric infrared cameras can establish apparent surface temperature of the problem, a classification system is often utilized based upon surface temperature, or temperature rise above normal operating temperature or ambient air temperature. This however can be an extremely unreliable classification method for a number of reasons including: emissivity and background energy; a lack of regard for failure modes and stressors; surface temperature variability with load and ambient conditions; temperature gradient from internal source to surface; and the presence of convection, just to name a few. Standards, such as NFPA 70B, try to address some of these issues by having very low threshold temperature limits, but this as well has issues including identifying an over-abundance of non-critical problems for immediate repair. This paper will present a risk assessment process and matrix which classifies electrical problems based upon a variety of factors affecting both probability and consequence of electrical component failure. Inherent in this process will be a discussion of understanding and analysing electrical connection failure modes and failure stressors, as well as consideration of both heat energy flow and stored energy rather than only considering surface temperature as a single point predictor of catastrophic failure.
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Gregory B. McIntosh, Gregory B. McIntosh, Roy Huff, Roy Huff, "Classification of electrical problems detected by infrared thermography using a risk assessment process", Proc. SPIE 9861, Thermosense: Thermal Infrared Applications XXXVIII, 98610T (11 May 2016); doi: 10.1117/12.2224261; https://doi.org/10.1117/12.2224261

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