A graphical method for safety assessment of grounding systems

Abstract

This paper presents a graphical method for safety assessment of grounding systems. For a grounding system to be safe, the maximum touch and step voltages should not exceed postulated safety criteria. The method presented in this paper is applicable to the safety criteria of the IEEE Standard 80 as well as the IEC-479-1. Both standards define safety criteria in terms of allowable body current. The allowable body current is then translated into the allowable touch and step voltages. Thus, safety assessment of a grounding system is referred to a procedure by which the actual maximum touch and step voltages are computed and compared to the maximum allowable (safe) touch and step voltages. Since the IEC-479-1 safety criteria are nonlinear, a graphical method is presented for safety assessment.