I'm curious if there has been research done on studying the harmonic content of an arc. I would like to know because I have seen some electronic relays with second harmonic blocking and I'm unsure if this would block the relay from tripping for an arcing fault.

The research I've seen done was focussed on using the wave shape as a means of detecting arcing faults. At low voltages (AFCI's) this works quite well but the lack of devices and the prevalence of other detection means indicates that it is not so successful at higher voltages.

If I remember correctly, Albert Marroquin, VP at etap, had some information on harmonics in arc fault currents. It looked pretty typical odd order. That said, the second order blocking is done in software, so I have to imagine if it did have an affect on arc fault sensing they would not enable the blocking there.

I have met Albert before. I'll give him a call and see what he thinks. I may also reach out to some engineers at SEL