...The nuances of inspecting electric equipment
We have a user’s forum on LinkedIn and have seen some discussion there on ultrasound detection of electrical emissions. There seems to be a bit of a misunderstanding about the use of ultrasound on electrical equipment. While there are many who use the technology to monitor high voltage equipment, there are many more who don’t think it will be useful on mid and low voltages. In fact ultrasound inspection can be performed on all voltages. The qualifying factor is the presence or absence of ultrasound. On voltages below 440 the type of emissions present will be either tracking or, more often arcing. On mid level voltages, tracking and arcing will be detected and on voltages above 1000, corona can be thrown into the mix. What confuses people is that there are a variety of issues that can pop up, some such as arcing, tracking and corona will produce detectable ultrasound while others that are related to resistance issues will generate heat but not ultrasound. If you know your system and your use both infrared and ultrasound technologies your chances of detecting a potential problem increases. If you rely just on infrared to detect heat related issues you’ll still be successful, but you are open to the potential of missing an issue such as tracking or even early stages of arcing where there is not a sufficient detectable heat differential. More importantly, as a safety issue, many infrared users defer to ultrasound as part of a procedure when inspecting enclosed equipment before opening panels. In fact ultrasound is an important component to inspection of lower voltage enclosed panels. There are many panels that have voltages of 480 or below. Even with IR windows there are some issues that might be considered hidden from view.
What about your experiences? How many of you have been using ultrasound to detect electrical emissions? What voltages and what types of problems have you found? Send us an email to firstname.lastname@example.org and we'll feature your findings in a future post.
For a great webinar on analyzing electrical faults, we suggest you view Joe Gierlach’s presentation: “Analyzing Electrical Sound Files”