Progress in step and touch voltage equations of ANSI/IEEE Std 80-historical perspective

This paper describes the evolution of safety criteria and the development of basic formulae for evaluation of the step and touch potentials in AC substations, from 1961 to the present time. Refinements proposed for the 1996 edition of ANSI/IEEE Std 80 are presented in a broader context of the continuing development of this popular IEEE Guide. Examples of a typical grounding design illustrate the difference in evaluation procedures given in the 1961, 1986 and 1996 (proposed) editions, and their practical impact on making the design safe.