Probabilistic Assessment of Step and Touch Potentials Near Transmission Line Structures

Step and touch potentials at transmission line structures are sometimes important parameters in the design of the grounding system. To have confidence in conventional (deterministic) methods of potential calculation, worst-case values of the design parameters must be assumed. This often leads to overly pessimistic results. A probabilistic approach enables more realistic values to be obtained with the same degree of confidence. A study has recently been performed to calculate the probability distributions of step and touch potentials in Ontario Hydro 230 kV and 500 kV networks. This paper describes analytical and computational aspects of the efficient program developed during the course of the study and presents a number of illustrative examples.