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Not sure where to attack this question from so any help would be appreciated. I was talking to a friend of mine who lays cables for a contractor and he was saying that in a recent job they laid pilot cables under ground next to High Voltage 11kV cables (in the same duct).

This got me interested, if a fault occured on the HV cable then an EMF would be induced in the pilot cable running parallel to it. I'm trying to calculate approximately what the induced EMF could potentially reach if I presume the pilot cable is laid a set distance away from the HV cable.

I'm really not sure where to start with this problem apart from calculating the magnetic field produced by the HV cable under fault conditions and from there calculate the induced voltage in the adjacent cable.

The B field produced by the HV cable would be = ((u0)*I)/(2*pi*r);

Knowing that voltage induced = d(phi)/dt, = -AdB(t)/dt, would A simply be the cross sectional area of the pilot wire, as going through this process is giving me incredibly small values of which I know a much greater voltage would be induced in reality.

I'm sure I must be missing something obvious like including the length of the pilot cable somewhere or something similar.

Any help greatly appreciated