If I am located in an area that is above 3000' in elevation how do I calculate or adjust my Restricted Approach Boundary?

I don't think there is any modification for altitude.

As the OP has implied, Note d under Table 130.4(E)(a) in NFPA 70E-2024 states that...

You need to use the Altitude Correction Factor specified in Table R-5 of OSHA 1910.269...
- search for references to "Table R-5" at this URL: https://www.osha.gov/laws-regs/regulati ... 0/1910.269 (Table R-3 explains how to use the correction factor from Table R-5)

It is important to note that 2024 NFPA 70E Table 130.4(E)(a) Note d indicates that the restricted approach boundary in Column 4 is based on an elevation not exceeding 3000 ft. This very much seems like it applies to all voltage levels. If you look in OSHA 1910.269 Table R-3, it clearly indicates that the "altitude correction factor" is not used for voltages from 50V - 5kV.

As such, do we assume that the voltage correction factor does not have an impact for voltages less than 5.1kV?