Voltage divider to measure Van De Graaff generator
Usually for high voltage they use Capacitance dividers rather than resistive dividers.





The 1st stands about 1m tall and rated for 100kV, 2nd is rated for 400kV is 1~2m 

and  2000kV not shown would be very tall,  really!

Double donuts reduce e-field gradient which otherwise would lower breakdown voltage.




When testing HVDC, it becomes more of a challenge for testing as ANY insulator surface oxidation becomes a transport for charge flow and reduced breakdown threshold, starting with repetitive partial discharge or "corona" is visible before BDV is reached.

Testing a 5MVA transformer 40kV, a 200kV bushing (insulator) for me arc'd at 90kVdc.  Since BIL200 only means for 200kV lightning impulse rating it failed below 100kV even after alcohol wipe, so I had to add 2nd bushing in series to test over 150kVdc for a contaminated oil insulation test I tried out.  It ticked like a FET relaxation oscillator and an AM Radio could easily hear it.  Even the epoxy paint got charged up over steel tank and gave little shocks touching it during testing.