3 ms·

> You are forbidden by law (and mandated to report) such arcs in Europe. You are forbidden by law to have an accident? This misunderstanding is probably becaus

> You are forbidden by law (and mandated to report) such arcs in Europe. You are forbidden by law to have an accident? This misunderstanding is probably because of my lack of knowledge, but what do you mean? > And trying to extinguish such an arc can be quite a challenge. I only read about them in this thread, so I’m probably missing something again, but isn’t it an instantaneous thing and not something you need to extinguish?

c_o_n_v_e_x 4y ago
>You are forbidden by law to have an accident? This misunderstanding is probably because of my lack of knowledge, but what do you mean? There are systems (permits to work, lock out tag out, risk assessments, etc.) in place to maintain worker safety mandated by law. An incident of this kind typically means that there was a failure with one of more levels of the system... Someone did something they weren't supposed to, they turned off the wrong equipment, they didn't turn off the equipment before working on it, etc. > And trying to extinguish such an arc can be quite a challenge. Once established, an arc can continue as long as current is still flowing. It's possible for arcs to continue and still be below the trip current of the upstream circuit protection. In non-catastrophic scenarios, you have mechanisms to "quench" an arc... one method is to use compressed air.. like blowing out a very hot, angry candle on a birthday cake.
Doxin 4y ago
You are forbidden by law to have an accident of this nature. Yes. If you do cause an accident of this nature you are criminally negligent no matter the circumstances leading up to the accident because it's your duty to ensure it doesn't. Of course you need to keep in mind that courts in Europe tend to not hold to the letter of the law quite as strongly as US courts seem to do. Laws like these are mostly so the judicial system gets booted up when something awful happens. Might still turn out that no one was responsible for the accident. Might turn out the boss of the guy throwing the switch was responsible. Or the equipment manufacturer.
- chrisseaton 4y ago
  Doesn’t make having an accident illegal make it more likely that people won’t report the accidents and won’t learn and improve?
  - Doxin 4y ago
    Making this sort of accident legal makes it definitive that people won't report it. Because there's no requirement to.
    - chrisseaton 4y ago
      > Making this sort of accident legal makes it definitive that people won't report it. Because there's no requirement to. Huh? No. Make it a legal requirement to report it. Then there is all the incentive to report it and no incentive not to. If it's illegal to have the accident, then attempting to cover it up is the most rational course of action, because if you can not report and get away with it then that's the only way you aren't punished. If instead it's just a legal requirement to report it, then reporting it is the most rational course of action, because you can report and then aren't punished.
      - Macha 4y ago
        Right, but inserting a legal incentive to do everything to prevent the accident is considered more important than inserting a legal incentive to report when it happens. If there was no consequences to having the accident, sure, you'd know all about the ones that happen, but there wouldn't be much incentive for investing in prevention
      - deleted 4y ago
        [deleted]
    - atoav 4y ago
      We are talking about accidents that mostly happen on the ownership border between house owners and grid maintainers. If you can cover up an arc flash there in such a way they will not notice on their next visit without dying, you might deserve to get away with it.
bcbrown 4y ago
> isn’t it an instantaneous thing and not something you need to extinguish? I'm not familiar with the details of this accident, but in general, not necessarily. Air is normally an excellent insulator. But when voltages are high enough, the molecules ionize, become conductive and transmit current. This is a path-dependent process, meaning that once it begins, the voltage can drop below what is required to begin the process while maintaining current. So an arc caused by a system with low capacitance (or total count of free electrons on the negative side) may quickly transfer all the free electrons, lowering the voltage enough to close the circuit. But anything connected to mains power will have an essentially infinite source of more electrons, meaning there won't be a voltage drop big enough to close the circuit. I'm being a little handwavy with the physics concepts, but hopefully the point is clear. This can be thought of as a sort of hysteresis: the dependence of the state of a system on its history. Edit: If you want to go down a rabbit hole, check out the solutions used in power substations as circuit breakers. It's not enough just to mechanically separate the connection, so they use systems like these: https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_breaker https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_br... https://www.codrey.com/electrical/air-blast-circuit-breaker/ https://www.codrey.com/electrical/air-blast-circuit-breaker/
MayeulC 4y ago
Maybe not only accidental arcs? If only to prevent accidental EMI and jamming of frequencies. There used to be spark transmitters: https://en.wikipedia.org/wiki/Spark-gap_transmitter https://en.wikipedia.org/wiki/Spark-gap_transmitter

c_o_n_v_e_x 4y ago

>You are forbidden by law to have an accident? This misunderstanding is probably because of my lack of knowledge, but what do you mean? There are systems (permits to work, lock out tag out, risk assessments, etc.) in place to maintain worker safety mandated by law. An incident of this kind typically means that there was a failure with one of more levels of the system... Someone did something they weren't supposed to, they turned off the wrong equipment, they didn't turn off the equipment before working on it, etc. > And trying to extinguish such an arc can be quite a challenge. Once established, an arc can continue as long as current is still flowing. It's possible for arcs to continue and still be below the trip current of the upstream circuit protection. In non-catastrophic scenarios, you have mechanisms to "quench" an arc... one method is to use compressed air.. like blowing out a very hot, angry candle on a birthday cake.

Doxin 4y ago

You are forbidden by law to have an accident of this nature. Yes. If you do cause an accident of this nature you are criminally negligent no matter the circumstances leading up to the accident because it's your duty to ensure it doesn't. Of course you need to keep in mind that courts in Europe tend to not hold to the letter of the law quite as strongly as US courts seem to do. Laws like these are mostly so the judicial system gets booted up when something awful happens. Might still turn out that no one was responsible for the accident. Might turn out the boss of the guy throwing the switch was responsible. Or the equipment manufacturer.

chrisseaton 4y ago
Doesn’t make having an accident illegal make it more likely that people won’t report the accidents and won’t learn and improve?
- Doxin 4y ago
  Making this sort of accident legal makes it definitive that people won't report it. Because there's no requirement to.
  - chrisseaton 4y ago
    > Making this sort of accident legal makes it definitive that people won't report it. Because there's no requirement to. Huh? No. Make it a legal requirement to report it. Then there is all the incentive to report it and no incentive not to. If it's illegal to have the accident, then attempting to cover it up is the most rational course of action, because if you can not report and get away with it then that's the only way you aren't punished. If instead it's just a legal requirement to report it, then reporting it is the most rational course of action, because you can report and then aren't punished.
    - Macha 4y ago
      Right, but inserting a legal incentive to do everything to prevent the accident is considered more important than inserting a legal incentive to report when it happens. If there was no consequences to having the accident, sure, you'd know all about the ones that happen, but there wouldn't be much incentive for investing in prevention
    - deleted 4y ago
      [deleted]
  - atoav 4y ago
    We are talking about accidents that mostly happen on the ownership border between house owners and grid maintainers. If you can cover up an arc flash there in such a way they will not notice on their next visit without dying, you might deserve to get away with it.

bcbrown 4y ago

> isn’t it an instantaneous thing and not something you need to extinguish? I'm not familiar with the details of this accident, but in general, not necessarily. Air is normally an excellent insulator. But when voltages are high enough, the molecules ionize, become conductive and transmit current. This is a path-dependent process, meaning that once it begins, the voltage can drop below what is required to begin the process while maintaining current. So an arc caused by a system with low capacitance (or total count of free electrons on the negative side) may quickly transfer all the free electrons, lowering the voltage enough to close the circuit. But anything connected to mains power will have an essentially infinite source of more electrons, meaning there won't be a voltage drop big enough to close the circuit. I'm being a little handwavy with the physics concepts, but hopefully the point is clear. This can be thought of as a sort of hysteresis: the dependence of the state of a system on its history. Edit: If you want to go down a rabbit hole, check out the solutions used in power substations as circuit breakers. It's not enough just to mechanically separate the connection, so they use systems like these: https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_breaker https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_br... https://www.codrey.com/electrical/air-blast-circuit-breaker/ https://www.codrey.com/electrical/air-blast-circuit-breaker/

MayeulC 4y ago

Maybe not only accidental arcs? If only to prevent accidental EMI and jamming of frequencies. There used to be spark transmitters: https://en.wikipedia.org/wiki/Spark-gap_transmitter https://en.wikipedia.org/wiki/Spark-gap_transmitter