Ground Gradient is a term used to describe the electrical field established around the current’s point of entry into the ground from SSG’S, downed conductor, or other source (for example, backhoe boom or truck outriggers) into the earth.
1. The electrical field created in these situations dissipates as the distance from the point of entry increases. The dissipation creates a difference in potential between any given two points in the electrical field. (See example illustration).
2. The difference in potential decreases rapidly as the distance from the point of entry increases.
Step potential describes the difference in potential that exists between two points in a ground gradient.
1. The difference in potential between a person’s feet can cause current to flow through a person’s body.
2. Step potential is usually negligible, except for where a downed conductor or severe fault to ground exists.
3. Step potential can be eliminated by keeping the feet together or by keeping only one foot in contact with the earth at a time.
A touch potential is caused when a person creates a current path to ground by touching an energized conductor, or ground lead when a fault exists. Touch potentials also exist when equipment is in contact with an energized conductor.
1. Workers on the ground and on a pole encounter touch potential more than step potential.
2. Touch potential is normally more severe than step potential due to the higher difference in potential encountered.