Probabilistic comparison and application of international electrical safety criteria

Investigations have been made into the impact of probabilistic aspects of the shock scenario, yet are rarely applied in practice. To provide reliable design criteria it is necessary to link the electrical shock safety criteria with acceptable risk levels applicable for people, in the context of an electrical power system under earth fault conditions. The paper addresses the basis of the various criteria and identifies inconsistencies that have been introduced when transferring laboratory data to published body current criteria. Interference theory and Monte Carlo simulation techniques are used to statistically appraise the actual level of safety afforded by various safety criteria when compared with the benchmark body current criteria. Directions for rationalisation or change are identified to ensure consistency with physiological criteria and to ensure that appropriate economic, as well as defensible levels of safety are applied to power system installations.