Neutral Grounding in MV Transformers Substations for Cranes Service

This paper analyzes crane power supply, typical distribution schemes in typical container terminals, the different system grounding techniques, and their impact on the service continuity of cranes. On the primary- and secondary-medium voltage (MV) distribution systems, provided by loop configuration, service continuity can be achieved also by TN-systems, with automatic disconnection of supply, due to the power source redundancy. The MV supplying system of a crane (lines of tertiary distribution, devices, machinery) constitutes an equipment under control EUC that has to be guaranteed to achieve or maintain a safe and integer state in case of fault events. On crane MV power supply lines with radial structure, the possibility to ensure service continuity consists in choosing an IT-system with high-resistance grounding (HRG). In fact, the faulted line can stay on service after a ground fault during the short time necessary to maintain the service of the faulted crane and contemporary to try in solving the fault or to remove the same crane.