Understanding IEEE 80: The Foundation of Substation Grounding Safety
IEEE 80 is the definitive standard for the design of grounding systems in AC substations. This article explains the key concepts, including tolerable body current limits, step and touch voltage criteria, and the role of soil resistivity in grounding design.
IEEE 80, 'Guide for Safety in AC Substation Grounding,' is the most widely referenced standard for substation grounding system design in North America. First published in 1961 and most recently revised in 2013, it provides a comprehensive methodology for designing grounding systems that protect personnel from dangerous step and touch voltages during fault conditions.
The foundation of IEEE 80 is the concept of tolerable body current — the maximum current that can flow through a human body without causing ventricular fibrillation. The standard uses the Dalziel equation to calculate this limit based on body weight and the duration of the fault current.
Step voltage is the potential difference between two points on the earth's surface separated by one pace (approximately one meter), in the direction of maximum potential gradient. Touch voltage is the potential difference between the ground potential rise (GPR) of a grounded metallic structure and the surface potential at the point where a person is standing while touching the structure.