The grounding of marine power systems: problems and solutions

Presently, most marine power systems are rated less than 600 volts and utilize an ungrounded power distribution system. This paper discusses various types of system grounding, grounding practices and characteristics of each and shows why high resistance grounding (HRG) should be adopted as a standard for ships The grounding of medium voltage systems is discussed since many newer ships have medium voltage systems to meet electric propulsion requirements. This paper will first discuss the theory and practices of system grounding in general terms. Next, existing standards for shipboard systems are reviewed and how adoption of HRG will meet these standards is discussed. Some design considerations for HRG are discussed, including charging current, cable selection, cathodic protection, and shore connections. The appendix describes a few examples of marine applications.