It's a disturbing video, for a number of reasons.
At first glance, it appears the person is a pro, wearing typical PPE. I can't see if he's wearing gloves, but it sure looks like he has a flash hood on ubder that hard hat. After that, his actions leave me completely confused.
The wire sure does look like triplex - two 'hot' wires wrapped around a bare neutral. The arcing you see is probably between the wire ends, rather than the ground they're laying on.
Still, if he's a lineman- where is his truck? I would have expected to see him in his insulated bucket, making the disconnection at the pole. I mean- what's his plan for the newly cut wires? If nothing else, at the pole there will be some slack, some space between the wires.
I think, instead, what we have is a simple downed power line, at 'residential' volyage, being toyed with by some untrained 'other trades' type. The 'hood' might be simple cold weather wear- a hard hat liner not properly installed in the hard hat. ZFor all I knopw, he was trying to cut the wires with pruning shears, and shorted the shears to the bare neutral.