[Thri4895o]

It is. Energy drain through induction, depends on conductivity of environment. By putting cables there, you increase energy loss on main line.

[TT-392]

The same goes if the fence is there and grounded though?

[bradfa]

I believe the intent matters. If you need a fence and you’re not trying to use the electricity then it is not theft. If your intent is to consume the power then it is theft.

Doing this kind of power harvesting off transmission lines is a standard Electric Power university course exam question for intro to transmission lines courses.