Arc Flash Calculations

[OCPD]

Hello all,

In arc flash for different voltage and respective equipment type the bus gap between conductors is different. As defined in IEEE 1584.

I was wondering if anyone would know what is the reason to have this difference in bus Gap. Is it only for example 5kV class equipment has a smaller gap between bussing than 15kV class equipment?

 

[wbdvt]

I believe that the different gaps are due to the construction of the equipment to prevent flashover. The dielectric strength of air is approximately 10kV per inch. As voltage goes up, the distance between phases and ground must be increased. I'm sure at some point the optimal distances for equipment were arrived at and standardized.