What Is Touch Potential

Good question. The terms touch potential and step potential are used mostly in the high-voltage power transmission systems. In typical high power transmission lines, the tower that holds the high-tension line may act as an 'antenna' and a receiver of high voltages or power (thunder, for example). If the tower isn't properly grounded, then the ground potential may rise to the levels that are dangerous. This is where the step and touch potential come into picture.

The Touch Potential is simply the potential between the point of contact (aka touch) between the energized object ( the tower, for example) and the point of contact between the object and ground ( say, the feet of the person touching the tower ). So if you imagine a person touching the tower with faulty ground; then the potential between the point where the person touches the tower and his feet would be called as the 'Touch Potential'. It could be dangerous enough to circulate major amount of currents; that may result into the death of the person.

The step potential, on the other hand would be the potential gradient between the person's feet standing nearer to the object of high energy.

Here's further reading on the topic of step and touch potential: #-Link-Snipped-#

An interesting discussion could be prevention of accidents that result from these types of potentials.