Modelling zone-substation-secondary earth fault scenarios with application to compliance with probabilistic safety criteria methods

Since the publication of the earthing guideline, ENA EG-0, the electrical industry response has been a mix of enthusiasm, resistance and compulsion to accept and implement the safety criteria methods proposed. In the large part it has been acknowledged as a positive improvement as the most thorough and modern treatment of earthing system risk analysis. While the risk based safety methods proposed in EG-0 appear functional with regard the assessment of substation primary faults, there is little doubt that assessment of Zone-Substation-Secondary risks appear higher than previously thought, particularly when compared to traditional methods. This paper proposes a method of modelling and evaluating a zone substation distribution network in order to better calculate the earthing risk zone substation assets create for individuals living within the influence of the installations. Moreover, the methods proposed give light to a possible solution to the conundrum surrounding any earthing system risk analysis where multiple fault scenarios exist.