For years now there has been a random occurrence that happens with seemingly any power tap device I have with protection circuitry in it where it will make a audible buzzing/arcing sound for a few seconds once in a while (like once every few days on average) and I would like to know what the most probable explanation(s) are for it.
The first time I had noticed it was as I was laying in bed, I heard a muffled arcing noise coming from my Tripp-Lite Isobar power tap. I found this concerning, so I removed it from use and later inspected the protection circuit board inside and found no evidence of burning/melting/arcing. There was no significant load being passed through the device, as is the case with all the situations below too.
Soon after, I noticed the same thing occurring with the replacement Isobar, so I began to wonder if it was specific to that model of power tap. I had another model of power tap with active protection circuitry I tried, Intermatic, and it eventually did it too. I had concluded it must be a local/building oddity.
Years later in a new home, miles away from the previous location, I began to notice it occurring again, first with the Isobars I had, and then coming from the APC Smart-UPS I now use instead. Curiously, it seemingly only occurs specifically from the protection device directly connected to the wall receptacle, never in downstream devices with protection circuits.
As for it being some sort of transient event, I am fairly confident, as in once case I happened to have a LED, dropping resistor and Triac circuit connected line-to-neutral after the power tap device with the protection circuitry. The Triac was off and the LED visibly dark, but when the buzzing started, the LED began to shimmer dimly in sync with the buzzing, and then went back off when the buzzing stopped.
