Cold ironing - power system grounding and safety analysis

Ocean-going vessels calling on ports all around the world, in general, use on-board diesel engine-generator sets for hotel power supply requirements. These ships, when docked at the ports, consume hotel power produced by the same generators resulting in air pollution. Shutting off these on-board generators and supplying vessel hotel power from the shore can reduce the diesel fuel emissions. This process, when shore power is provided to the vessel auxiliaries by shutting down its on-board generators, is called cold ironing. This technology has been used by the military at naval bases for many decades when ships are docked for long periods. However, recently, as the world´s vessel fleet is increasing at a steady pace, vessel calls at specific ports are becoming relatively more frequent. In addition, vessel hotel power requirements have increased, and thus the concern of on-board generator emissions during docking periods has become an important air pollution issue. This paper describes electrical power system of a cold ironing project in which barge is used to mount a unit substation and cable management equipment. At present there are no industry standards for cold ironing power system design, especially the grounding of the floating ungrounded ship power supply system. This paper highlights the main features of cold ironing power systems, with emphasis on personnel and equipment protection by an adequate electrical grounding system.