Ultrasonic testing of MV switchgear <20dB requirement?

[irishguy2010]

does anyone have any ideas for what standards & tables I should be referring to when performing an ultrasonic test on online MV switchgear. I have found several references to 20dB limits, but they don't call out any standards.

[ElectricalTestTech]

does anyone have any ideas for what standards & tables I should be referring to when performing an ultrasonic test on online MV switchgear. I have found several references to 20dB limits, but they don't call out any standards.

Hey Irishguy2010,

I am a certified level 2 ultrasonic inspector. "Sounds" like it carries weight, pun intended. But the truth of the matter, is that the company I work for, our Project managers don't know how to sell the service of ultrasound. The 2nd issue is that they don't buy the more expensive equipment that can data log and plot out the sound waves. So if you are using an older ultrasonic detector with an analog meter, you don't get accurate measurements.

From my experience performing a few ultrasonic inspections, you are listening for specific sounds. "Bursts" of sound could be arcing. You can describe corona as a frying egg sound or popcorn popping sound. The decibels are not very important as understanding and training your ears to the specific sounds. It all may sound "fuzzy" at first, but you may hit a spot that doesn't sound "fuzzy" anymore. That may be a spot to investigate.

I hope this helps you.

[SecondGen]

does anyone have any ideas for what standards & tables I should be referring to when performing an ultrasonic test on online MV switchgear. I have found several references to 20dB limits, but they don't call out any standards.

Where do the 20db limit references come from?