well, in short, this electrical transformer lowers the input voltage by 26 times, but because of P = VI (power = volts × amps) the amps must go up by 26 times, and P = I2R (power dissipated (heat output) = amps squared × resistance, assuming R is constant) makes them become very very violent in an arc fault (kinda like a short circuit; the power gets concentrated in one place) on the secondary (“output”) side.
in reality its a bit more complicated and R is probably not going to be constant but either way that little 2 means you are going to have a very bad time if this secondary (which is almost certainly supplying gobs of power) has an arc fault.
the 391 cal/cm^2 and “Flash hazard at 18 in” means that if you have your hand 18 inches (45 cm) away from the secondary, it is estimated that every square centimeter of something (skin) exposed in the direction of it will receive 391 calories of energy in an arc fault. one calorie is the amount of energy needed to heat one milliliter (1 cm3 of water) by 1 degree celcius.
dividing out the cm2, this means that such an arc fault has enough energy to theoretically heat your exposed skin up uniformly by 391 degrees celcius to a depth of one centimeter. again, reality differs—it will not be exactly 391 calories, it will not be uniform, and your skin will be beyond burnt!
of course, that’s not even getting into the explosions and stuff that would also take place that result in the “NO SAFE PPE EXISTS” label, where PPE is personal protective equipment.
the solution to eliminating the hazard here if you absolutely must get near this transformer is to turn it off (deenergize it) so you don’t need the PPE. but there have been some interesting situations in history with immensely hazardous objects that were deemed necessary to approach and couldn’t be disabled, where it was dangerous to the point those around simply didn’t wear PPE because it would do nothing. the harvey casino bomb comes to mind!
Arc flash incident energy IS the explosion. That’s the size of it. Anything over 40cal is considered dangerous (no PPE exists)
The distances are based on the covers being off as opposed and someone working on it. NOT during normal operation. It is generally safe to be near electrical equipment if it is not being worked on/opened up.
This is just… woosh.
Right over my head.
well, in short, this electrical transformer lowers the input voltage by 26 times, but because of P = VI (power = volts × amps) the amps must go up by 26 times, and P = I2R (power dissipated (heat output) = amps squared × resistance, assuming R is constant) makes them become very very violent in an arc fault (kinda like a short circuit; the power gets concentrated in one place) on the secondary (“output”) side.
in reality its a bit more complicated and R is probably not going to be constant but either way that little 2 means you are going to have a very bad time if this secondary (which is almost certainly supplying gobs of power) has an arc fault.
the 391 cal/cm^2 and “Flash hazard at 18 in” means that if you have your hand 18 inches (45 cm) away from the secondary, it is estimated that every square centimeter of something (skin) exposed in the direction of it will receive 391 calories of energy in an arc fault. one calorie is the amount of energy needed to heat one milliliter (1 cm3 of water) by 1 degree celcius.
dividing out the cm2, this means that such an arc fault has enough energy to theoretically heat your exposed skin up uniformly by 391 degrees celcius to a depth of one centimeter. again, reality differs—it will not be exactly 391 calories, it will not be uniform, and your skin will be beyond burnt!
of course, that’s not even getting into the explosions and stuff that would also take place that result in the “NO SAFE PPE EXISTS” label, where PPE is personal protective equipment.
the solution to eliminating the hazard here if you absolutely must get near this transformer is to turn it off (deenergize it) so you don’t need the PPE. but there have been some interesting situations in history with immensely hazardous objects that were deemed necessary to approach and couldn’t be disabled, where it was dangerous to the point those around simply didn’t wear PPE because it would do nothing. the harvey casino bomb comes to mind!
Wow, thank you for this in-depth explanation! :3
It all sounds very dangerous to me, tbh.
Arc flash incident energy IS the explosion. That’s the size of it. Anything over 40cal is considered dangerous (no PPE exists)
The distances are based on the covers being off as opposed and someone working on it. NOT during normal operation. It is generally safe to be near electrical equipment if it is not being worked on/opened up.