What are touch potential and step potential, and why are they hazards near outdoor high-voltage sources?

• A. Touch potential is the voltage you could experience by touching a live surface; step potential is the voltage difference between your feet; both can cause shock if not controlled
• B. Touch potential is the difference between ground and air; step potential is the voltage of the battery
• C. They are the same concept
• D. They are only concerns indoors

Answer: (A)

Touch potential and step potential describe how voltage differences around energized outdoor equipment can drive current through a person. Touch potential is the voltage difference between something you could touch that’s energized and the surrounding ground. Step potential is the voltage difference between the two points where your feet are standing on the ground.

These differences are hazards because they can create a current path through your body if you touch an energized surface or if your feet are on ground that’s at different potentials. Near outdoor high-voltage sources, the earth can have a gradient of potentials from a fault or downed line, so simply reaching out or stepping across a small distance can cause current to flow, risking shock or more severe injury. The concepts aren’t about “air vs ground” or about indoors only; they specifically describe dangerous ground-based voltage differences that can exist outdoors near high-voltage sources.