# Power line inductance on an electric fence

by Creini
Tags: electric, fence, inductance, line, power
 P: 2 Hi, Hope this is the right forum to ask this question. I have an electric fence running parallell to an electrified railway (25kV@50Hz, varying current). I'm trying to figure out how to calculate the induced voltage on the fence to figure out how long the fence can be before it becomes dangerous. As far as I can make out this will be dependant on how well the fence is earthed, how far away from the current carrying conductor(s) and the permeability of the material in the fence? Most of the examples I can find is on how to calculate the inductance between two (or more) current carrying conductors. Should I consider my fence as a conductor? And then calculate the mutual inductance between the two? To calculate the mutual inductance I should calculate the flux linkages$$\varphi$$? I think the flux linkages per meter is the same as the flux per meter as there is only one link (N=1). Which would give me: d$$\phi$$=($$\mu$$*I)/(2$$\pi$$x) dx Wb/m = $$\varphi$$ in this case(?). Do I then integrate $$\varphi$$ from the current carrying conductor to the fence? e.g. if the fence is 5m from the conductor, would I integrate from the outside of the conductor (e.g. 0.05m) to 5m? $$\varphi$$cond,fence = ($$\mu$$*I)/(2$$\pi$$)*ln(5/0.05) Or do I integrate just around the fence? E.g. from 4.95 to 5.05? Or am I completely wrong? Hope this made any sense. /Mattias