| ▲ | ericd 6 hours ago |
| Something to consider, and something I got a vivid demonstration of while playing with solar panels, DC arcs aren't self-extinguishing, unlike AC arcs. At one point I stuck a voltage probe in, and the arc stuck with it as I pulled the probe away. It also vaporized the metal tip of the probe. My understanding is that DC breakers are somewhat prone to fires for this reason, too. |
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| ▲ | bigiain 6 hours ago | parent | next [-] |
| Heh - I vaporised a fairly large soldering iron tip (probably 4mm copper cylindrical bar?), when I fucked up soldering a connector to a big 7 cell ~6000mAHr LiPo battery and shorted the terminals. Quite how I didn't end up blind or in hospital I don't know. It reinforced just how much respect you need to pay to even low-ish voltage DC when the available current was likely able to exceed 700A by a fair margin momentarily. I think those cells were rated at 60C continuous and 120C for 5 seconds. |
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| ▲ | ericd 6 hours ago | parent | next [-] | | heh man, I'm glad you got out of that easy, I definitely wore safety glasses 100% of the time after my experience. I think a lifetime of experience with dangerous wall outlets and harmless little 1.5V/9V DC cells teaches us the wrong lessons about DC safety. I've since heard stories of wrenches exploding when they fall across EV high voltage battery terminals. Wrenches aren't supposed to be explosive. The electricians I was working with also told me stories about how with the really big breakers, you don't stand in front of it when you throw it, because sometimes it can turn into a cloud of molten metal vapor. And that's just using them as intended. | | |
| ▲ | scheme271 5 hours ago | parent | next [-] | | A bunch of those big breakers require two people. One person in a flash suit and another with a 2m long pole around the first person. That way if an arc flash happens, the second person can yank the first person to safety without also getting hurt. | | |
| ▲ | pocksuppet 5 hours ago | parent [-] | | Why don't they use the pole to flip the breaker from 2m away? | | |
| ▲ | defrost 5 hours ago | parent [-] | | Ruins the fun and interrupts instilling respect deep into the bones of interns. Allegedly While on "work experience" from high school I was put on washing power lines coming straight out of the local power station near the ocean - lots of salt buildups to clear. Same deal, flashover suits and occasional arcs .. and much laughter from the ground operators who drifted the work bucket close. |
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| ▲ | bluGill 6 hours ago | parent | prev | next [-] | | Amps - the old 48vdc telco data centers vaporized wrenchs once in a while. | |
| ▲ | jacquesm 6 hours ago | parent | prev [-] | | Those harmless 9V DC cells can do a lot of damage if you use them right. |
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| ▲ | jacquesm 6 hours ago | parent | prev [-] | | You got super lucky. | | |
| ▲ | bigiain 5 hours ago | parent [-] | | Yep. Super super lucky. I suspect my reading glasses are the only reason I can still see anything. | | |
| ▲ | jacquesm 5 hours ago | parent [-] | | I have a couple of those narrow escapes one of which led me to put a significant chunk of Eastern Amsterdam out of power. Another involved Beryllium oxide. 9 lives are barely enough. | | |
| ▲ | swamp_donkey 2 hours ago | parent | next [-] | | Ah! Perhaps you are a member of the gigawatt club? Eligible for entry once you have accidentally tripped off 1000 MW of load or generation! No sweeping that under the table | |
| ▲ | bigiain 5 hours ago | parent | prev [-] | | I would read that book... | | |
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| ▲ | toast0 5 hours ago | parent | prev [-] |
| > DC arcs aren't self-extinguishing, unlike AC arcs. At one point I stuck a voltage probe in, and the arc stuck with it as I pulled the probe away. It also vaporized the metal tip of the probe. It would have self-extinguished if you waited long enough for the probe to vaporize. |
