Does anyone else use the ultrasound for Corona detection. If so I had what sounded like corona in a exterior sub station transformer but the sound appeared to be on the 480 V side lines which is unusual because of the low voltage. I used the corona camera to see if anything could be detected in the vecinity (may be noise bouncing), turned off outside lighting and the noise went away, turned the outside light back on and the noise came back. Chances are its not corona but some other type of high frequency disturbance and I am not sure what it might be or where to look for an answer. Any thoughts would be appreciated.

Craig

Hint, take your ultrasound device and scan a neon light fixture. Hear the sound produced by the ballast. It should very familiar to what you heard in the substation.
But, your right about 480. Corona can be heard by ultrasound from 1khz or higher, IR cannot see it under 240kHz.

The neon sign I belive is different. I have a neon sign transformer I use for practice to create corona. I didnt know neon signs had ballasts?. I have a 9,000 volt neon sign transformer but they range up and down from there but are generally over 3,000 volts which will produce corona. The light I am talking about is 277 volts with some type of interference out at the sub.

Craig

This message has been edited. Last edited by: Craig Casler,

Jim,
You had me wondering so I did some further research on the neon sign. As I suspected the neon signs do not have ballasts like your interior lighting 110,208,277. They have transformers due to the high voltage needed to make the signs glow. The crackling you are here in the neon signs is likely corona and may or may not be a potential problem. I have also done some further investigation on my problem which is leading to EMR or RFI I have to investigate further to see if either of these is the culpret. Not sure at this point any imput would be helpful.

Craig

Yes, your right. I have a 7500 volt transformer I use for my corona & arcing electrical trainer. I can easily produce corona discharge with this unit. I have actually shot it with the IR Camera and obviously NO heat was seen, yet the corona could easily be heard.

Craig,
We finished an in-house, day and a half training course for the CTRL UL101 with all the attachments. 10 people were trained and 9 out of ten found the same loose 24v control wire in a MCC. It was amazing because I thought airborne ultrasound would not detect low voltage either, especially that low!
Good In = Good Out

No one said that it cannot hear that low (24v). An arc is an arc, it is friction in the air. A disturbance or turbulence in the air. Ultrasound typically can be used to find low to high voltage. Most of the topics you hear or read are on corona. Corona can be detected with ultrasound at 1kv or higer. However, arcing or tracking at much lower voltage, may possibly be detected. MCC is another area to be using your ultrasound detector. Good find and please keep everyone informed of what you find in the future.

WoW great information. I will take a closer look out at the sub since this is where I heard the disturbance and may be I will find it expanding my search.

Thank you both for your help.

Craig