SOLUTION

Touch potential: Touch potential is the voltage difference between a person’s arm and the feet, caused by the voltage gradient due to fault or induced current. It is assumed that the current passes through the heart and therefore this potential should be kept to near zero to safeguard personnel who might accidentally come in contact with equipment and structures in a switchyard or substations.

Touch potential measurements are similar to fall-of-potential measurements in that both measurements require the placement of auxiliary electrodes into or on the earth. Spacing the auxiliary electrodes during touch potential measurements differs from fall-of-potential electrode spacing, as shown in Figure.