What’s inside a lightning arrestor?

What is inside one of those things? The folks over at Northstreetlabs have set out to answer just that question. You’ve seen these things before, and if you’re uneducated on the subject like myself, you just assumed they were there to stop a possible connection from a power line to the pole/building to which it is attached. Apparently that is part of their purpose. When presented with lightning, however, they turn to conductors allowing the lightning to pass to ground.

You can see their teardown in video form, as well as an explanation of how exactly they work on their site.

14 thoughts on “What’s inside a lightning arrestor?

  1. And they explode quite violently when hit with a mazzive strike.

    I was 1200 feet away from a substation when it was struck with a really fat lightning bolt. Most everything looked like it exploded, but later it was found that all the Suppressors like this blew up and then the safety breakers released too slow causing extra arcs.

    http://youtu.be/SBzRmWeC6Ds This is what it looks like when those safetys fail, and those happened on 4 of them after the lightning strike.

    1. Your link connects to a Star Wars Trilogy video. While interesting, you might still want to fix your link.

    2. Arrgh! This one is of the safety fail and the resulting arc.

      Imagine 4 of them in heavy rain after a massive lightning strike. IT was jumping to fences and other devices.

      1. If you look on the right side of the switch there is porcelain up top where the conductor is. These are either vacuum bottles, or filled with sf6 to break the current just before the switch opens. It clearly failed to do its job. I’m assuming the workers knew this to be the case since they had the hindsight to grab the video camera.

  2. I am smarter for having read and seen that. I thought they were strictly for insulating the power line from the pole. And I always wondered what was inside. Now I know!

    1. There are things on the pole just to insulate from the conductor, called insulators. They look very similar to lightning arrestors. I will take some pictures later of each.

    2. Actually these look very similar to insulators, which are much more common. I will snap some pictures later to show you what I mean.

  3. Fascinating, thanks for posting. I’ve also seen the results of what happens when they blow up and arc, but never knew what was inside.

  4. Wow – that vid above is interesting. Back about ten years ago a transformer down the street from me got blown off a pole due to a lightning strike. But the lines sat there are arced away for a good 2 minutes until the power went out.

  5. At the utility I work for, lightning arrestors are used inside the substation (in addition to spark gaps) to protect substation equipment like circuit breakers and transformers.

    The lightning arrestors are the grey insulators to the left and right of the picture.

      1. Not a very good picture but just the closest thing to me at the moment.

        Arrestor left
        insulator right

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