Neutral grounding in MV industrial power distribution systems: Italian standards comparison

This work analyzes resistance grounded systems, particularly three standards used in Italian industries: low resistance grounded, medium resistance grounded and high resistance grounded systems are discussed and compared. This comparison is aimed at analyzing the behavior of the three different standards in the presence of the most common fault, that is the line-to-ground fault and the conflicting requirements of service continuity and hardware integrity. The risk-based approach has been used in order to quantify probabilities of the hazardous events identified according to diverse grounding designs whose decision-making factor is assumed to be the distribution network maintenance effectiveness. Protective devices and apparatus availability demonstrate furthermore critical and protection design as well; thus operation in a life cycle approach will turn out to be the validity of the new EN CENELEC 61508 as reference design norm.