I'm not trying to steal enegrgy, our company wants to propose such a device to the electric corporation which is our client. The toroidal core, made of two halves, will be attached around the high voltage conductor.
I definitely don't have much experience in high voltage, although I do successfully design electromagnetic actuators, solenoids and even a DC motor, but those are low voltage products and pretty straightforward to design and simulate (I use FEMM and JMAG). This project is not really my cup of tea, but once we have an initial concept of cource it will be supervised by proper EEs.