Let’s Blow Up An Explosive Lightning Arrestor

Lightning is some nasty stuff. Luckily, it doesn’t have a very long lifespan. [BigClive] decided to tear down an 11KV lighting arrestor used in power distribution systems. The fiberglass core has silicone rubber water-shedding disks that make the unit look sort of floppy, but inside is some serious hardware.

To protect the circuit, metal oxide varistors shunt high voltage from a lightning strike to ground as you’d expect. The interesting part is how the device deals with failure. It would be a disaster if the device shorted the 11KV power line to ground for any length of time due to a fault. To prevent that problem, a resistor heats up when struck by lightning and triggers an explosive charge that disconnects the ground wire and releases a flag to indicate the failure.

[BigClive] triggered the charge in the video below. So if you like to see things explode in a bucket of water, you’ll enjoy the video.

Amazingly, this isn’t the first lightning arrestor tear down we’ve seen (although the embedded link is dead). However, it seems most hackers don’t want to stop lightning, they just want to photograph it.

37 thoughts on “Let’s Blow Up An Explosive Lightning Arrestor

    1. A politician would be aware that you can just buy effective explosives and/or their constituent ingredients directly and legally without the pretense. A fear mongering kitten rapist would try to scare people that safety equipment will be used to build bombs.

      P.S. I am not referencing you Shakipu, just supplying a more descriptive title for the 3rd party which you referenced.

      1. Our current politicians understanding (or lack of) of the difference between an “assault rifle” and a “rifle” should be proof enough that politicians don’t know their asses from holes in the ground. This case included…

      1. The disks add creepage distance. The higher your voltage, the greater minimum creepage distance you need.
        Some small insulators have drip points to shed water. This one looks like water would be able to cling to it if it were hanging vertically. I would guess that if there is enough water (with dissolved impurities or dirt/grime), to conduct, it would just boil off.

      2. I actually work with high voltage for a living with some of the brightest minds in the field. Those are as the others are telling you, for increasing standoff distance for high voltage. Not for water deflection, regardless of what the poster at stack exchange is spewing.

        Besides WATER IS NOT THAT CONDUCTIVE. It’s the contaminates in the water from being exposed to the air that makes it conductive.

        But that shape has ZERO to do with water.

        In fact we use deionized water for cooling parts at high voltage and after being in contact with high voltage, not more than a couple of inches away the water touches hard ground. In fact, DI water flowing through plastic pipes will create a static charge all its own if not grounded.

        In fact, in fact there are tons of high voltage parts and insulators that are not even designed to be exposed to rain or the outdoor elements that have that exact shape. TO INCREASE THE HV STAND OFF DISTANCE so that any corona or arcing will not creep along the surface and cause the device to “break down”. And that can happen if the device is perfectly clean and dry if an overvoltage condition were to occur.

        It’s ok to be wrong.

  1. I was disappointed that he didn’t show the flag that pops out when these detonate. I’ve seen one of these explode on the high-tension lines that go through the right-of-way on my grandparents’ farm. I don’t recall seeing the flag, but it did sound like a shotgun.

  2. with today’s day in age with terrorism i am surprised that anyone can get ahold of the explosive charged disconnector i would think they are carefully monitored by the government.

    he said that if he cut or hit it that the charge could go off.

    what’s to keep a terrorist from doing the same thing with a spring loaded hammer or cutter or even firing a bullet at it?

    1. They are not carefully monitored by the government, because they are not an explosive. The manufacturer of the device requires ATF licensing for manufacture of commercial pyrotechnic devices.
      The devices contain about the same amount of powder found in a 12 gauge shotgun shell. There would be no point in tying to obtain these for making a bomb when you could easily just buy a pound of black powder, or extract the smokeless powder from shotgun shells or other firearm rounds.

    2. I doubt they are monitored by the government. Not that it matters since BigClive is located in the UK where the rules are a bit different than the US.

      Besides, he was erring on the side of caution. It’s possible it could explode if he cut into it. It’s also possible that it wouldn’t.

      1. We used to by small amounts of un-mixed binary “flash powder” from a costume store nearby when we were kids. That stuff was amazing. Especially when contained… Lucky none of us lost a finger or limb!
        I would have figured that stuff was outlawed long ago. I am astounded after reading the ATFs rules on it.
        An older wiser me gets enough death defying excitement at work. I think I’ll just leave that stuff alone :)

        1. I used to buy (and make) flash powder as a kid too. Back then we could buy all sorts of fun things. Flash paper was always my favorite.
          But flash powder is a pyrotechnic mixture, and although there are different compositions, is generally a type of black powder with low sulfur content and fine aluminum dust (the German black aluminum was the best) added to it for flash effect and higher deflagration speed.
          The binary high explosive mentioned is similar to ANFO (ammonium nitrate – fuel oil mixture), but instead of fuel oil, very fine aluminum dust is used as the fuel. The mixture does not detonate if put to fire. It requires a large, fast shock to cause it to detonate. Most center-fire rifle rounds that have sufficient muzzle velocity will detonate the mixture upon impact of the bullet. I use .308 Winchester and .223 Remington, but using aluminum dust in the mixture with a smaller particle size will increase it’s shock sensitivity, so (sometimes) a high velocity .22LR round (like CCI Stinger) can also detonate it.

    3. In half of the world including the US people can buy unlimited bullets, that each and every one carries ‘an explosive charge’ which is more powerful than this thing (after all a bullet is lead and flies hundreds of yards/meters whereas this thing just separates and dangles.

      Equally most places sell fireworks, which also have black powder and is capable of more explosive power than this.

      And then there are various ways to combine household chemicals to make an explosive.
      And many spray cans use an explosive gas as a propellant (and which can also be purchased in pure form in canisters for various uses)
      And all houses have a pipe with explosive natural gas going into them (even seen a house after a gas explosion? That’s more than a detached plug)

      Then we have gasoline, which propels cars by a continues range of millions of explosions for many years.

      Or in other words, explosives are ubiquitous..

    4. I had 150 of these elements in a bucket for years. I removed them from arresters because the MOV will pass HF but the explosive element will not. I was making coupling units for powerline comms installations. Some utilities chose to install another MOV in parallel with the coupling unit, some chose not to.

    5. If you did fire a bullet at it, or whatever, then worst-case you might cut the power on one of the feeds. Other feeds would take over, the electric company would notice, and they’d send out a guy with a new one. So you’ve possibly created slightly less annoyance than static electricity.

  3. I recognized the multimeter from the picture before I even read that it was [bigclive]. By a bizarre co-incidence I have just spent the last half hour watching him tear down some poundland LED lamps. Perhaps I need to get out more.

  4. ahh clive XD at least with this one he did it safely…

    “ahh, just throw the 240v heater into the tub, it’ll warm it up”

    PS: if it bubbles before it heats up or if it bubbles only at the connections it means the water is LIVE… and soon you wont be! lol

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