Ground planes with high voltage circuits.

So I'm making a little PSU for a particular microphone that requires 120Vdc. Due to regulation and a high degree of smoothing the AC input will be 140Vrms and this approx. 200Vdc in parts. I'm interested in a ground plane to both keep ground impedances low and to fill the board with copper otherwise it's going to be very sparse. I have used 1mm clearances across the entire board including the ground plane. Should I go more? Can someone point me to some regulations that commercial products have to stick by?

Thanks

look here

https://www.smps.us/pcbtracespacing.html

Also make sure that said 120V cannot ever get on the shield and chassis of the microphone. You certainly don't want your performers to get shocked on contact.