What is Step Potential

This is the potential generated between the feet of a person or animal closer to the surface or area of an earthed rod/wire/object carrying current.
During earth faults, high amount of current flows to the ground and the nearby ground surface beside the earthed object. If a person is standing within the area closer to the grounded object, a potential can be generated between the feet (foot to foot) and the difference in potential causes current to flow through the body which is dangerous.
So, the wider the distance between the feet (foot to foot), the higher the potential difference and the higher the current being induced. The smaller the distance between feet, the lesser the potential different and the smaller the induced current into the body. Equipotential points have zero potential different. So, with the feet being tight together, the points are at the same potential (equipotential point). This is the reason why birds are not electrocuted when they stand on transmission lines. Because their frets are so tight together such that there exist a zero potential different between them. Hence, no current is induced into them.
So, technicians should be aware of step potential when working in:

• earthed zones, 
• during earth fault, and 
• areas of underground canalisation.

So, technicians should always wear their safety equipment when working in these zones.
This is illustrated below.