What is the distance between the 10kV busbar and the casing
The NEC requires a minimum spacing of 12 inches (305 mm) between busbars, but this can be reduced based on the busbar current and configuration. And for general industrial control equipment, voltage range 301-600, shortest distance is shown as 1/2" with this same value being shown through oil or air over surface. Between live parts of opposite polarity, 251-600V, Through air gap is 1", Over surface is 2". If you can place bare conductors 1/2" apart and meet the test requirements for 15kV equipment, that is fine. And before you conclude that I'm being ridiculous, remember that we do this every day in vacuum interrupters.
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