The highest I’ve used it for is 75kV DC, though it’s designed for a maximum of 150V at the meter, which equates to an input voltage of 150kV. High voltage probe design The above is how it was ...

[Ludic] measured the capacitance value with a standard meter, but it wasn’t clear ... your homemade cap might not survive the high voltage. If you want lots of capacitance (but perhaps not ...