I was glad to see that you added another thrilling video and photo to your utility section. I would kill to see an actual video of that 115kV disconnect opening with two phases continuing to arc until the switch was reclosed. Those bushings are about 5' tall, so that arc is a good 8-10 feet long.
Even when removing grounds from an 'unenergized' line often results in large inductance arcs. On another site, I found a photo of a lineman removing a ground from an unenergized 345kV line. He is using a twenty-foot long fibreglass pole to grab the gound and pull it off. The resulting arc is about ten feet long and growing as he pulls the ground away from the conductor. There is another three-phase set of 345kV next to this line, so the voltage is induced in the line.
The video with the fuse meltdown was cool also. The arc seemed to be rather docile and maybe lower voltage/amperage? It must have finally melted the fuse holder down to ground, causing an upstream breaker to open, killing power to the station. That arc was not as nasty as the one on your video with the transformer overheating and catching fire. THAT was a super nasty full-amperage arc. I wish you could get more info as to what was arcing over on that video. With all that black smoke while the arc is still going, makes me believe that it was burning a transformer, or oil breaker...something with oil, as the bus wouldn't smoke like that. Please keep posting HV utility photos and videos. Your 500kV video is still the king of them all!