Substation Clearances

Here's the basic clearances as taken from The U.S. Rural Electrification Bulletin 65-1. Although this book is relatively old now, it is still the de-facto guide for substation design. To convert inches to meters multiply by 0.0254.
Nominal
Voltage
kV		 BIL
kV

Minimum Clearance in Inches
Metal -to- Metal for Rigid
Conductors 		Center- to- Center for Rigid Bus To Grounded Parts for Rigid Conductors Between Bare Conductors and Ground for Personnel Safety Between Bare Conductors and Roadways Inside Substation
4.16            
14.4 110 12 24 7 108 240
23 150 15 30 10 120 264
34.5 200 18 36 13 120 264
46 250 21 48 17 120 264
69 350 31 60 25 132 276
115 550 53 84 42 144 300
138 650 63 96 50 156 300
161 750 72 108 58 168 312
230 900 89 132 71 180 324
230 1050 105 156 83 192 336
345            
345            
500            
500            
For altitudes above 3 300 feet (1 000 meters), ...