Plasma arc - GIF

**ToolTalkBot** · Oct 23, 2024, 09:51 PM

Plasma arc.

Previously:

Cesium plasma - GIF
Plasma in slow motion - GIF
Sodium plasma - GIF

**hemmjo** · Oct 25, 2024, 07:51 AM

what would make that happen? Maybe moist, salty air? Or perhaps, but unlikely, downed high voltage lines somehow energized those lower voltage lines?

**Hoosiersmoker** · Oct 25, 2024, 08:16 AM

Looks like the ghost of a linesperson traveling down the lines. Happy Hallowe'en!

**Karl_H** · Oct 25, 2024, 08:56 AM

She watches it for 20 seconds, until it is 3 or 4 houses down the road. Then it is urgent to "get inside!"

**BuffaloJohn** · Oct 26, 2024, 11:21 AM

Originally Posted by hemmjo

what would make that happen? Maybe moist, salty air? Or perhaps, but unlikely, downed high voltage lines somehow energized those lower voltage lines?

Probably a lightning strike and a cascade of arresting devices failing (or completely missing). The air is humid (notice all the flooding). Salty air, maybe, but we can't tell from the video.

We - as high school students in the early 70's - used neon sign transformers to make a Jacob’s ladder. If you have enough voltage, you get the air between the conductors to ionize and the arc is formed from the high voltage and the ions. It needs to be alternating current so that the arc can sustain itself. If it is just direct current, you can get repeated sparking, but if the arc is sustained for too long - it becomes welding and the electrodes melt.

Also, to step up the voltage, you need alternating current - transformers don't work on direct current. Well, this power line is AC and is much higher than the voltage entering the house.

BTW, this is the principle behind florescent lights just more controlled. You probably don'r want anyone saying "oh, my god" multiple times when you turn the kitchen lights on...

**Gadgeteer** · Yesterday, 11:38 PM

This was a great video capture. I witnessed one of these, going by about 40' from me, several decades ago. St. Elmo's fire. Never thought I'd see one, but I never thought I'd see a Bigfoot, either.

**desbromilow** · Today, 05:41 AM

phase to phase fault started further up the line, and as the arc was established, the line impedance causes it to move towards the source (transformer) in order to reduce impedance - the closer it gets to the source, the more energy is released into the plasma ball, and it keeps moving until it gets to the source, or the supply protection (eg fuse) trips.

Given the flooding, I'd guess that the initial phase to phase fault may have been caused by a tree branch contacting the wires. - I was tree felling some years ago and a phase to phase fault caused by a 3/16" thick branch (with leaves) was enough to create this exact effect - it traveled about 400m before popping the transformer fuses.

**Hoosiersmoker** · Today, 06:12 AM

Originally Posted by desbromilow

phase to phase fault started further up the line, and as the arc was established, the line impedance causes it to move towards the source (transformer) in order to reduce impedance - the closer it gets to the source, the more energy is released into the plasma ball, and it keeps moving until it gets to the source, or the supply protection (eg fuse) trips.

Given the flooding, I'd guess that the initial phase to phase fault may have been caused by a tree branch contacting the wires. - I was tree felling some years ago and a phase to phase fault caused by a 3/16" thick branch (with leaves) was enough to create this exact effect - it traveled about 400m before popping the transformer fuses.

So, not a ghost then?