Page here
video by itself here
Pretty cool. Here’s my guess at the explanation:
The pair of wires in a two-wire transmission line, like power lines, experience a force pushing them apart. See this video. The case when the current is in series is the one that matches the power transmission lines, so there’s a force pushing power transmission wires apart. There will also be a force pushing on the arc, which is acting as a wire shorting the lines, pushing it along the line. It’s like a sideways Jacob’s ladder. In a Jacob’s ladder, the heat of the arc causes the arc to rise*, but here, since the wires are parallel instead of spreading apart, the arc just moves down the line, and doesn’t break.
I suspect that there’s somehow a higher voltage on the power lines than they are designed for, causing the arc in the first place.
- ETA: I’ve always assumed it’s the heat, but maybe the Lorentz force is a factor in a Jacob’s Ladder as well.
Guess
looks like something happened around the corner causing an arc between the lines. And then the arc traveled back down the lines until it reached a transformer or a capacitor that would have been the explosion.
It looks like terrible camera work, someone with no idea how to properly frame the video or keep the action in the shot. Because of that, it’s nearly impossible to tell what’s going on with the powerlines.
This site has pictures of a circular Jacob’s ladder, but uses a magnet to get a strong enough force to make the arc move. But it has a link to a different circular Jacob’s ladder with enough power that the Lorentz force is enough to move it without using a magnet. The audio is in German, so I don’t know what he’s saying.
The article says wind knocked out the power lines, so my guess is that wind blew the lines close enough together to cause an arc to form, but not close enough that the lines actually touched (otherwise the short would have tripped the line).
Then the arc traveled down the line, just as you and others have said, until it happened to hit a transformer (maybe a capacitor but more likely a transformer, IMHO). It either blew the transformer or finally drew enough current to trip the line, because after the kaboom everything went dark.
The transformer is converting of the order of 30 kV (10 , or 30 or 110 kV ? whatever !) to 200 to 415 volts three phase (Depending on the standards at that part of the world. Its not important.)
The lines we are looking at the local distribution mains power… The ones that provide 110 or 240 volts single phase ( up to 415 volts between phases ).
There is 30 kV on one of the power lines and its arcing to another. For some reason this is not triggering the fault protection - the current may be limited by the exact nature of the fault, details unknown to us.
The air gap between these local distribution lines is large enough enough to hold off higher voltage , eg 30kV, but somewhere along the way, the arc occurred, as it had to, because the gap is reduced at various places.
Arcing is ionising the air … Ions turn the air into a conductor !. The ions diffuse into the air, and as the ions move toward the source of the fault, the arcing moves… So you see the arc travel toward the source.
When the arcing reached the transformer, well the transformer has an input of the 10kV or more… the ionised air shorted out the input of the transformer…
That created the bang, and the fault that triggered a fault detector … A solenoid back at the power switch yard threw the switch to cut off power to that part of the city.
My SWAG.
A high voltage power transmission line was blown or somehow connected (tree branch falling) to a lower voltage distribution line. (unseen by us but it’s been known to happen)
The distribution line which was built to carry 2,4 or 12 KV now has 34KV to possibly 161KV on it and Flashes over phase to phase or phase to ground. The transmission protection devices (relays) are either set wrong or the distributions system appears to look like just a heavy load to those devices.
So the flash continues to burn and moves across the line as the wind blows the ionizing gas of the arc down the conductors.
This is why power system designers don’t like to put their transmission lines and distribution lines on the same poles but sometimes do so to save cost and sometimes to keep urban areas from having twice as many poles.
I’ve seen that in real life. In my case, it was triggered by a lightning strike on a residential transmission line. The arc lasted about 20 seconds, and ended with an explosion. Green fire, and a hum that rattled my colon before the final bang.
Nothing much to add otherwise. I’ll confirm the arc/fireball is a dielectric breakdown of the air between the conductors, but I haven’t heard the cause.
The video was waaaaaay cool, but would have terrified my wife if she witnessed it.