It sounds a little like something I almost worked one once which involved attaching a load cell to a high tension power line. My idea was to use optical power transfer through a fiber optic line with a beam splitters so that an optical modulator at the load cell end could send the data back.
The optimal solution to that would be to have a small ac/dc non-isolated converter from MV to 5V for example, that powers the cell amplifier, ADC, and a low power radio link transmitter (LoRa maybe).
That’s what I have in prototype right now, a non-isolated converter from MV (12kv.. 20kV) to 5-12V that can put 300mA to 1A (still in testing). Of course it has to withstand impulse lightings as if it were an inductive transformer and other fun stuff in the standards: for phase to neutral MV transformers for example IEC 60044 states that a voltage increase of 90% must be tested during 8h (in case of a ground fault in isolated neutral systems). IEEE C57.13 however states otherwise. Anyway I still have to do a lot of testing in this thing.
Now I’m studiying the possibility of making the same but isolated for low power appplications.