Ground Step and Touch Potential Calculations

Where switching or transformation involving high-voltage circuits occurs, appropriate grounding systems must be employed to ensure the safety of people in the area. During a line-to-ground fault event, fault currents may return to their source through the earth. This flow of current raises the potential of grounding system above that of the earth, causing two possibly hazardous situations:

  1. Step potential – refers to the voltage difference between two points on the ground surface in the path of a person stepping through the area.
  2. Touch potential – refers to the voltage difference between an above-ground metal surface (such as the post of substation fence) that may be touched by a person, and the ground surface in the area.


Step and touch potentials must be limited to values which ensure the safety of individuals who may be present in the area. This is accomplished by design of a grounding system which meets these conditions during the highest possible fault currents. Due to the large number of calculations involved in arriving at a suitable ground system, the design is best performed with the assistance of a computer program. 

Please contact us to discuss grounding design for your facility.