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0xDEADBEEF
#9
Feb28-12, 02:31 PM
P: 824
Just a quick calculation:

The threshold for feeling a current seems to be around 1 mA. The current flowing through the body for DC current is:

[tex]I=\frac{C_{\text{droplet}}\cdot R \cdot A \cdot U}{V} [/tex]

Where [tex]C_{\text{droplet}}[/tex] is the capacity of a rain drop. R is the rate of the rainfall in m/s. A is the exposed area in [tex]m^2[/tex], U the Voltage and V the volume of a drop.

If we use drops of 1mm (it gets more dangerous the smaller the drops are because the number of drops goes up fast). Heavy rainfall of 0.1m/h. U = 135kV. An area of [tex]1m^2[/tex] I get a current of [tex]I=1.5\cdot 10^{-2}mA[/tex]. Alas you wont feel a thing. And this is assuming that you really manage to get the whole rain that hits you charged, in reality the powerline is much slimmer than your body and most of the rain will not be charged. The current is usually AC, so drops tend to cancel each others charge. Oh and if you calculate something where you get a deadly current of something like .1A. Imagine this goes for every meter of wire. A short powerline of 10km would have losses of 133 Megawatt! That is a fifth of a small powerplants output. I think they would turn off the line if that ever happened.