Mishap at the Electrical Substation

As a little kid, I used to think electrical substations would make really awesome jungle gyms. This video helpfully demonstrates why 5-year-old Maggie was an idiot.

This is the Eldorado Substation near Boulder City, Nevada. What you're seeing: A substation like this one is connected to long-distance transmission lines and electricity has to be very high voltage to travel on those. The substation "steps up" the voltage so the electricity can travel. Everything at a substation is hot, in that shock the bejeezus out of you sense. So that maintenance can be done, substations are built with switching functions that allow you to disconnect and reconnect various parts of the system in modular sort of way. The big, crazy spark in this video happened when some of the switching mechanisms failed. The Arcs 'n Sparks page at Stoneridge Engineering explains what happened next...

There's some technical jargon involved in this, but I thought you'd find it interesting and it gets the point across.

During normal operation, the switcher will first open the SF6 interrupters which disconnects the HV circuit so that the air break switches can open with no current flowing. Once the air break switches completely rotate to the "open" position, the SF6 interrupters then reclose. Normally, this sequence insures that the air break switches operate de-energized and arc free.

Instead, here, the air break switches opened while the current was still coming through.

The arc stretches upward, driven by rising hot gases and writhing from small air currents and magnetic forces, until it easily exceeds 100 feet in length. As impressive as this huge arc may be, the air break switch was really NOT disconnecting a real load. This arc was "only" carrying the relatively low (about 100 amps) magnetizing current associated with the line reactor. The 94 mile long transmission line associated with the above circuit normally carries over 1,000 megawatts (MW) of power between Boulder City, Nevada (from the massive generators at Hoover Dam) to the Lugo substation near Los Angeles, California. A break under regular load conditions (~2,000 amps) would have created a MUCH hotter and extremely destructive arc. Imagine a fat, blindingly blue-white, 100 foot long welding arc that vaporizes the contacts on the air break switch and then works its way back along the feeders, melting and vaporizing them along the way. Still, you've got to admit that this "little" 33 MVAR arc is certainly an awesome sight!



  1. “Everything at a substation is hot, in that shock the bejeezus out of you sense.”

    Everything after the comma is gibberish. Even if you switch sense to senses, I’m still clueless. Missing word? Wrong word?

    1. “Everything at a substation is hot, in that shock the bejeezus out of you sense.”

      “Everything at a substation is hot, in that shock the bejeezus out of you sense.”


    2. “”Everything at a substation is hot, in that shock the bejeezus out of you sense.” Everything after the comma is gibberish. Even if you switch sense to senses, I’m still clueless. Missing word? Wrong word?”

      This really only needs one word change and some dashes:
      Everything at a substation is hot, in the shock-the-bejeezus-out-of-you sense.

    3. You may also be missing the fact that “hot” sees occasional use as jargon meaning that there is current running through it.

    4. “Everything in that substation is hot, in that shock-the-bejeezus-out-of-you sense” is what I think was meant.

  2. This isn’t a mishap. This was an intentional decoupling. I forget the exact reason, but you can tell it was planned from the whoop at the end of the video, even electrical engineers get to have fun sometimes.

    1. From what I’ve read and how I understand it, something was going wrong with the switching, but the engineers weren’t sure what. This video is from when they went out to the field and ran a test to see what was happening. So, yes, the test was planned…but the arc was not, and it was the result of a system failure that the test was meant to catch.

  3. A scientist working on a new energy source creates more than he bargained for. Dr. Quest receives a radio request for help from the man, who is cut off. Now Benton, Race, Jonny, Hadji and Bandit must investigate and defeat an invisible entity that seemingly feed on everything in its path!

  4. That’s cool and all, but planned. I’ve got a question sorta related. Does anyone know what causes the random (seemingly) flashes coming off substations? I live across the street from one in downtown Toronto. About once every 2 months, there’s a flash that comes off the station (may be more often, but i’m not ALWAYS home). It’s usually bright enough to see quite clearly, and comes with the same ‘whiny electrical’ noise. It seems to do it more in the winter than in summer, so maybe related to static electricity?? I wish I could capture it on film, but I don’t have 2 months to dedicate to sitting watching the place 24/7…

    Any ideas?

    1. Is the flashing associated with drizzles or fog? I know the dust on an insulator can get damp and give the electricity a path to travel.

      1. Usually…but then again, sometimes not. But there is always ‘some’ moisture in the air, so it could still be part of it!

      2. You know, that’s a very likely explanation. I often see little flashes due to accumulated ice on the catenary wires that power the electric trains and the electric streetcars in the winter.

    2. I have heard transformers making large amounts of noise. I have also seen them pop with a really bright flash. Maybe that is what you have seen?

  5. I dunno. . . unless someone gets caught in the blast and winds up with electro-powers, I can only be so impressed.

  6. @#12 yeah this video was making the rounds in at least 2004. The neat thing here is the fractal patterns created by the arc. I’d like a better explanation of that.

  7. Around high voltage lines a coronal discharge develops which is accentuated by dust on the insulators and moist air. You can hear an ongoing crackle and the occasional pop.
    When a circuit is opened and the wiring or loads constitute inductance, the magnetic field collapses all at once and very high voltages are the result. If resistance was zero the voltage would be infinite hence the arcing. In smaller substation switches, dry nitrogen gas is released to blow out the arc.
    Power line lose is a function of current squared hence the need for high voltages to minimize current.

  8. If I understand well they have to switch off the low voltage first before they can switch off the big switch on the high voltage side otherwise the big switch will fry.

    May be there is an arc because even though the low voltage is down there is still some substantial residual voltage in the high voltage circuit. Is it the problem?

  9. It’s interesting how parts of it, and even the whole thing, instantaneously vanish and are replaced with a new formation. I don’t think it would occur to me to do that if I were animating it.

  10. Great post, Maggie! I’ve always wondered what goes on at those things. I knew they were for stepping up the voltage, but I didn’t know about all the moving parts–or that arcs could fly!

  11. This reminds me that I’ve been meaning to order some SF6 to play with. In addition to being good at quenching arcs, it is inert enough to inhale safely, and dense enough to lower your voice–the opposite of helium. But it is kinda pricey.

  12. This is interesting.. I actually work for an electric company north of Dallas and part of our training during our first year there (mind you, I’m only in the GIS department and not on the line crew) is to witness an arcing demonstration right up close.

    Something like that arc at the substation is extremely devastating, even with no load on the circuit.. we were watching an arc being built from a 5 kVa transformer onto a metal rod that was able to tunnel a hole in a hot dog about the size of a pencil in about a second. That is enough to kill somebody.. the temperatures in these arcs can reach higher than temperatures on the sun, especially when you’re dealing with 600 amp lines or even substation/transmission line arcing.

    Scary stuff

  13. My 6-year-old daughter also happens to be named Maggie. It took me a few seconds to realize Maggie Koerth-Baker wasn’t calling my daughter an idiot. :)

  14. Seeing as how looking at a welding arc can damage your eyes, I’d like to know at what distance these huge arcs are dangerous to view, and for how long?

  15. In the early ’80s when I was in my early teens, a few of the burnouts from my school (i.e., potheads, no pun intended) broke into and explored a nearby power substation. Out of the four kids, one was killed, and a second was horribly scarred. That kind of ruined the whole hanging out around high-voltage thing for me.

  16. ah yes, good old Sulfur Hexaflouride…

    Wont be seeing too many more substations using that stuff, it being a fairly potent greenhouse gas and all. But the kW quenching capabilities of SF6 are hard to match by either air or oil interrupters.

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