A closer look at the grounding of shore-to-ship power supply system

To minimize the pollution that ships generate at ports, major ports all over the world are facing the challenge of upgrading their shore power infrastructure in order to make the provisions for shore-to-ship power supply systems. This process of supplying shore power to ships while turning off their on-board generators during berthing is called cold ironing. At present, there are no industry standards or recommended guidelines for cold ironing power system grounding design. Ship power is such that it requires a medium voltage power system with multiple parallel feeds, power plugs, receptacle assemblies and a flexible cable management system. This paper establishes the technical basis for designing a resistance grounding method for a cold ironing project, which would provide protection for both the operator and equipment in case of a ground fault anywhere in the system. A discussion of homo-polar grounding system for the ship's on-board power system is included. A system grounding design method to minimize stray current through the ship hull is presented. This paper intends to provide technical input for the new IEEE Draft Standard P1713 on Cold Ironing.