1363.04 REQUIREMENTS WHEN NOT INSULATED.
   Whenever any metallic conductors forming parts of current-carrying electric circuits are not insulated from the ground, such circuits shall be designed, installed, operated and maintained so that the average potential difference during any ten consecutive minutes between any two points 1,000 feet apart on such metallic conductors will not exceed one volt, and further, so that the average potential difference during any ten consecutive minutes between any two points more than 1,000 feet apart, on such metallic conductors within the limits of the City will not exceed seven volts.
(1979 Code 91.73)