EMI Aspects of Low Voltage Power Distribution Systems for Ships

In many mission-critical systems, such as naval vessels, the power supply system is insulated. An insulated, or unearthed, system has no connection, or via a high impedance, to earth, and often the neutral is not used. An insulated system has drawbacks with respect to electromagnetic compatibility compared to the usual earthed power supply system, mainly due to the limited use of filtering possibilities. This paper provides a qualitative analysis of the advantages and disadvantages of insulated power systems and neutral earthing and the impact on electromagnetic compatibility.