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?
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.
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.
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.
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_br...
https://www.codrey.com/electrical/air-blast-circuit-breaker/
The high cal rated PPE does indeed look like bomb squad gear.
A small arc, not even dangerous to touch, could have the same energy rating as a gigantic one if you measure the first over a year and the second over a millisecond.
When you say in Europe, normally that refers to an EU Regulation or Directive (since other legislation varies wildly in member states). What are you referring to here?
What is the mechanism by which an object would be propelled when hit by such an arc?
> The pressure wave created by an arc flash explosion has the force of thousands of pounds per square inch. This is powerful enough to knock down or throw nearby workers and at the same time cause damage to the eardrums, lungs, brain and other vital organs.
https://www.electricityforum.com/iep/arc-flash/electrical-ar...
(I didn't know that, and just found that explanation while looking for an answer to your question.)
A different risk is that electric current passing through the body could cause muscle convulsions, which could also cause someone to move or fall suddenly or erratically.
It's basically a small explosion.
The hot metal then ignites in air adding even more heat to the explosion.
Arc flashes like that can burn with 10000 to 15000 degrees celsius and if you are close by not only will they send you flying, you are probably dead before you hit the ground.
And trying to extinguish such an arc can be quite a challenge.