Firstly, thanks Nigel, yes I am looking for magic, its called electricity and the witchcraft is mutual inductance. lol.
I probably should have explained it a bit better as everyones imagination is going crazy, no I don't work for the CIA and I'm not trying to steal electricity for a crop of herb.
I need to power remote monitoring equipment that gets installed at water treatment sites, often underground so solar and wind are no good.
There is always power at the sites but rarely power outlets. I'm not an electrician so I cannot connet an outlet myself, legally. (and no I can't get an electrician out there.)
Currently I'm using batteries and can get upto 2 weeks, but some remote installations require longer deployments. unfortunately some of the sites are upto 4hrs from civilization so battery changes are time consuming and expensive.
It is a private power grid so connecting a transformer on the line is not an issue, and definitely not illegal.
The method described by GRIM sounds perfect now I just need to know how to do it? if I can purchase/make a system that will work?