A Practical Probabilistic Method to evaluate Tolerable Step and Touch Voltages

A simplified probabilistic method to calculate the risk of the human body withstand voltage to be exceeded by step and/or touch voltages appearing during abnormal system fault conditions is presented in this paper. The determination of density probability functions and cumulative distributions are done by using characteristic parameters of well known typical probability functions. This process allows the treatment of human body resistance, foot-to-ground contact resistance and fault clearing time as three independent random variables defining the human body withstand to the passage of shock currents.. A comparison between the results obtained through field measurements and those calculated by the proposed method is also presented.