static electricty problem
September 16, 2009 6:40 AM Subscribe
Would a faraday cage protect sensetive electronic equipment from ambiant static electricty during a lightning storm?
Ideal Faraday cage? Yes.
Real-life Faraday cage? Now we need to know what you mean by "ambient static electricity." A real-life Faraday cage is like to attenuate, not kill entirely. This is the fundamental problem with lightning w/r/t staying alive -- even a 90dB drop in intensity isn't enough if the lightning bolt could kill you a billion times over.
You would also have to deal with grounding implications -- the large potentials in a lightning storm would lead to steep gradients in voltage everywhere including the ground.
posted by range at 8:34 AM on September 16, 2009
Real-life Faraday cage? Now we need to know what you mean by "ambient static electricity." A real-life Faraday cage is like to attenuate, not kill entirely. This is the fundamental problem with lightning w/r/t staying alive -- even a 90dB drop in intensity isn't enough if the lightning bolt could kill you a billion times over.
You would also have to deal with grounding implications -- the large potentials in a lightning storm would lead to steep gradients in voltage everywhere including the ground.
posted by range at 8:34 AM on September 16, 2009
Isn't the greater danger in a lightning strike the spike in line voltage, rather than the induced current that the Faraday cage is supposed to mitigate?
posted by electroboy at 8:37 AM on September 16, 2009
posted by electroboy at 8:37 AM on September 16, 2009
Here's the problem...
MegaAmps x milliOhms = Kilovolts.
If your Faraday cage has ANY resistance, the amount of current delivered with a big ass lightning strike would develop large potentials across the cage and those might be enough to break down whatever insulation the interior air provides. So, safe? Meh? Maybe for stuff that isn't meat, but I would want to test it out on fauxScot's ancient (though cute!) carcass.
I think the question, if framed to just inanimate electronics is that ambient fields are less of a concern than direct strikes. Lots of shielding and various active components can protect against reasonably low energy.
I think I'd just give up on the idea of protecting anything from a direct strike. Lightning does manage to jump a spark many miles, sometimes. That's one hell of a lot of potential. Good insurance is probably cheaper than any cage that would do it.
posted by FauxScot at 9:40 AM on September 16, 2009
MegaAmps x milliOhms = Kilovolts.
If your Faraday cage has ANY resistance, the amount of current delivered with a big ass lightning strike would develop large potentials across the cage and those might be enough to break down whatever insulation the interior air provides. So, safe? Meh? Maybe for stuff that isn't meat, but I would want to test it out on fauxScot's ancient (though cute!) carcass.
I think the question, if framed to just inanimate electronics is that ambient fields are less of a concern than direct strikes. Lots of shielding and various active components can protect against reasonably low energy.
I think I'd just give up on the idea of protecting anything from a direct strike. Lightning does manage to jump a spark many miles, sometimes. That's one hell of a lot of potential. Good insurance is probably cheaper than any cage that would do it.
posted by FauxScot at 9:40 AM on September 16, 2009
The question isn't really about a direct strike, is it? A Faraday cage, grounded or not, will reduce e-fields inside of it. If it's a sphere, even better.
posted by lalas at 11:12 AM on September 16, 2009
posted by lalas at 11:12 AM on September 16, 2009
Response by poster: No the question is not about direct strikes, the situation is a combination of components linked together to provide a constant and uninterrupted 220v electric supply, most insterlations average between 4-8kw and are composed of:diesal genirator,sinewave inverter-DC charger,deep cycle lead acid battaries,sola panels and wind turbine.
It is the more deilcate components that suffer the damage during these storms i.e the pcb's inside the inverter chargers and i can ony asume this is static because in all cases we have never found any everdence of a direct hit by lightning.
posted by 1joseywales at 2:55 PM on September 16, 2009
It is the more deilcate components that suffer the damage during these storms i.e the pcb's inside the inverter chargers and i can ony asume this is static because in all cases we have never found any everdence of a direct hit by lightning.
posted by 1joseywales at 2:55 PM on September 16, 2009
Best answer: The failures you are seeing are almost certainly not due to static electricity and a faraday cage will do nothing to prevent them. Your system consists of a lot of large de facto antennas that are capturing large voltage and current transients from lightning that are being conducted into your power system through the power conducting wires. You do not need a direct hit by lightning. The antennas (turbine, panels, all the wires connecting them) capture the lightning's electrical energy out of thin air just like a radio signal. The lightning could even be some distance away.
You need lightning and voltage surge suppressors on the wires going into and out of your inverter box. If this is a do-it-yourself system, it is possible that the inverter was never designed for open exposure to these conditions. If that is the case, you would be better off replacing it with a power inverter with voltage suppression protection built in. It may be possible to cobble up some sort of protection devices external to the inverter, but that is not the ideal solution. You should also have surge protection at all of the other components to your system. The best place to divert the surge is near its source and you have a lot of possible sources.
posted by JackFlash at 5:47 PM on September 16, 2009
You need lightning and voltage surge suppressors on the wires going into and out of your inverter box. If this is a do-it-yourself system, it is possible that the inverter was never designed for open exposure to these conditions. If that is the case, you would be better off replacing it with a power inverter with voltage suppression protection built in. It may be possible to cobble up some sort of protection devices external to the inverter, but that is not the ideal solution. You should also have surge protection at all of the other components to your system. The best place to divert the surge is near its source and you have a lot of possible sources.
posted by JackFlash at 5:47 PM on September 16, 2009
In my 4 years working as a system designer at a lightning protection company, I have learned that there are 2 integral parts to protecting electronics from lightning storms.
The first is a quality surge suppression system. Indirect strikes (even ones that are miles away) can cause surges through ANY service entrance to a site including electric, data, and phone. If a site is not subject to direct strikes, this will be all you need.
If a site also needs to be protected from direct strikes (this may or may not be true in your case), then there is a need for a lightning protections system that will harmlessly direct lightning strikes around the structure (essentially a Faraday cage designed to intercept lightning strikes).
With both of these in place and properly designed (UL certified), 99.999....% of all lightning damage can be averted.
posted by tdreyer at 4:57 AM on September 24, 2009
The first is a quality surge suppression system. Indirect strikes (even ones that are miles away) can cause surges through ANY service entrance to a site including electric, data, and phone. If a site is not subject to direct strikes, this will be all you need.
If a site also needs to be protected from direct strikes (this may or may not be true in your case), then there is a need for a lightning protections system that will harmlessly direct lightning strikes around the structure (essentially a Faraday cage designed to intercept lightning strikes).
With both of these in place and properly designed (UL certified), 99.999....% of all lightning damage can be averted.
posted by tdreyer at 4:57 AM on September 24, 2009
This thread is closed to new comments.
posted by forforf at 7:14 AM on September 16, 2009