Minimum Distance Between Bus Bars

There are different standards in different parts of the world.

Here in North America I believe it is 1 inch of surface area between live parts, 1/2 inch in free air (been a long time since I had to look it up).

By designing switchgear for many years, this is certainly a concern in regards to distance between different phases along with creepage distance. You might be surprised to know the low voltage requirements are very much as our friend described below (not much distance). One of the criterias in terms of standarization is the bus bar insulators on the market, They start out at 1 inch and increase according to design voltages. The other concern is maximum short circuit available in the system for determining the distance between the horizonitally. In answer to your question, I suggest you use 2". This allows for bolt and nut intrusion and is a safe number and pretty much standard up to 600 volts a.c. You might go on line and punch in www.Eagle.org, sign up and download rules for classing steel vessels or IEEE-45. There are many regulatory bodies that give you these answer from that to the IEEE Buff Book, and many, many more. Stick with the 2 inches and you'll be good to go!

Most of the DB Board have 60mm to 75mm minimum distance between each busbar, but this is not the standard minimum requirement distance for the busbar. These distance is for your own maintenance works, where you need to tighten these busbar connection (busbar to busbar) in years later or you need to tighten the busbar holder inside your Sub Board in case if the busbar holder found to be loosen.

There are times that you need to tighten the blot and nut at the incoming compartment to your breakers or your cables that connected to the busbar.If you have too small distance between these busbar, later stage you will find difficulties to do your maintenance works.

There are some standard requirement as per standard minimum clearance depends on the material group and pollution degree of the insulating material in addition to this, space required to do some work on bus bar are also to be considered,

Its also vary from country to country and manufacturer to manufacturer.