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Fantastic example of an arc flash: When two phases of a power line are bridged (like a branch crossing them), an arc of electricity is formed. If it's big enough, the air between them ionizes, and instead of being an insulator, it becomes a conductor. https://twitter.com/CWatkinsWDSU/status/1361353720689221635
It'll move down the wire until it reaches either a circuit breaker that trips and prevents it from moving forward, or a transformer... which then explodes in a brilliant flash and a bang.
Arc flashes/flashovers are exceedingly dangerous.
Arc flashes/flashovers are exceedingly dangerous.
A "runaway" electrical arc has negative incremental resistance: that means as the temperature increases, electrical resistance decreases.
As it gets hotter, it draws more and more current. We're talking plasma-generating heat, here.
Nearly 19k°C/34k°F.
As it gets hotter, it draws more and more current. We're talking plasma-generating heat, here.
Nearly 19k°C/34k°F.
In addition to that, the arc vaporizes most things (like the metal conductors, etc.), and when things are rapidly phase shifted from solid to gas, that creates a volume expansion, aka: an explosion.
Not to mention the intensely burning light radiation from the arc blast itself.
Not to mention the intensely burning light radiation from the arc blast itself.
Arc welding is effectively a controlled use of a low-power arc flash to melt metals together.
Also, if you've ever seen an incandescent lightbulb go out with a flash and a pop, that's a tiny example of an arc flash.
A huge one happened in Astoria, Queens in Dec. of 2018.
Also, if you've ever seen an incandescent lightbulb go out with a flash and a pop, that's a tiny example of an arc flash.
A huge one happened in Astoria, Queens in Dec. of 2018.
This happened when a ConEdison transformer failed, creating a 138k-volt arc. The blue-green glow is from aluminium vaporizing.
(Aluminium burns bright white at lower temps because of the aluminum oxide burning, a pretty light blue at higher temps, but that's a different thread.)
(Aluminium burns bright white at lower temps because of the aluminum oxide burning, a pretty light blue at higher temps, but that's a different thread.)
Remember... electricity is a great convenience that is also fun and exciting.
It's also horrifically, insanely dangerous.
It's also horrifically, insanely dangerous.
