Generally... they are rated in such a way so to ensure that voltage rise on them under fault conditions is within a certain limit. To limit voltage rise at the fault levels that a panel is designed to withstand, it is the resistance of the bar that is important.
Panels are designed to handle a certain level of fault current normally measured in symmetrical RMS amperes.
If you are talking about a specific panel, you will need to check whatever "certification" the panel has. The
requirements for the bond/earth bus in a panel will be spelled out in
the requirements of the certification agency.
In Canada... one of the accepted standards that will point you to more information is... CAN/CSA C22.2 No.29-M1989 - Panelboards and Enclosed Panelboards.
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Joe Contractor to Electrical Inspector, "What do you mean you are going to make me follow the code?".
Grounded Bus Bar Ratings
Re: Grounded Bus Bar Ratings
