POTENTIAL GRADIENT/VOLTAGE GRADIENT:-

Change in voltage/ potential with respect to the distance under line to ground fault  called as voltage /potential gradient.

STEP POTENTIAL:-

Under the line to ground fault condition if any person come in that area then the current flow from his step or legs then it is called as step potential

TOUCH POTENIAL:-

Under the  same condition mention in above topic if the wire touch to pole and then some one touch that pole then current flow from his /her  hand to ground then its called as touch potential.