13,000 volts in a high voltage underground vault.
4160 V is my limit.
Do doorbells count?
I once had a 120-volt outlet that was showing as 87 volts on my Suretest. Huh? Oh. Wrong type of voltage drop. Nevermind…
Not as a H.I., of course, but in my previous life I had responsibility for all of our mill industrial systems up to 110 kV. Of course, none of the contact work at that level was done energized. The highest voltage I ever worked with “hot” (for testing, etc.) was 480 v.