A friend of mine was telling me about a storm that knocked down a power line over at their place, and it got me to thinking. Why are downed power lines dangerous? I don't see any good reason for it.
It seems to me that if they can put a GFI on a hair dryer that will kill power within a fraction of a second if it falls into the sink or tub and shorts out, they ought to be able to do the same thing to a power line. Is there any reason why the basic concept can't work at that scale? Or if not, why aren't they standard equipment on power lines?
Best Answer
Even if you could cheaply and efficenctly engineer a GFI to work on 250,000V high current lines, and you could shut down the grid to fit them how often do downed lines hurt people compared to lawn mowers going over extention leads?
Even then I suspect that if you could disconnect the other end of the line there would be enough charge stored in the cable between you and the GFI to make you very unhappy