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Thread: Trending Electrical System Exceptions

  1. #1

    Trending Electrical System Exceptions

    Other than "what infrared camera should I buy?", probably the most common questions asked of me by thermographers is "what temperature threshold should I assign to electrical components and connections?"

    OK, so it's not in exactly those words... it's more like "how hot should a circuit breaker be? What severity rating do I give to a hot connection when it's 70°C? How do I rate faults using temperature? Over what period should I trend a hot spot? Do I record ALL components so I can trend them over time?

    Unlike many organisations our philosophy around electrical system exceptions is to NEVER trend them or assume that temperature severity equates to a timeline to failure. Electrical system exceptions are by their very nature unpredictable and as such whenever a thermal exception is found, rather than utilise temperature severity, a more reliable assessment is to give consideration toward the safe and profitable operation of the facility. After all, if it is a genuine exception, it won’t fix itself and will eventually fail. Assuming that the degree of "hotness" is a good indicator of that is a misnomer.

    Anecdotally we find that customers that still use traditional temperature thresholds and temperature severity criteria for prioritising repairs still report a significant number of failures that “they didn’t get around to in time”. While there are certainly very hot components that will/do fail as anticipated, they don’t openly recognise (or realise) that many of the lower temperature exceptions also failed.

    We are well aware that most in the industry, particularly manufacturers who sell thermal imagers that “measure temperature” continue to promote the easily digestible paradigm that if it’s hotter, it’s surely likely to fail quicker. While I agree that holds true for most mechanical systems scenarios, there are many electrical system failures that won’t exhibit the same trend.

    The illustration below is case in point as to the dangers of trending electrical system exceptions.

    Name:  hypotherical fualt curve.jpg
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    This is also a great article that discussed this topic with some great insight.
    QIRT-2014-019-electrical system exceptions.pdf
    Brenton Ward
    Level III Infraspection Institute Certified Thermographer
    Level II Airborne Ultrasound

  2. #2
    excellent garph this is great knowledge for me and other

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