Potential failure mode of equipment operating with multiple grounds in direct current distribution systems

The authors discuss the impact and the means of addressing various options for resolving the consequences of the postulated failure mode of electrical equipment operating with multiple grounds in a direct current distribution system. The postulated failure mode is based on events within the nuclear industry that resulted in the issuance of Nuclear Regulatory Commission (NRC) Information Notice 88-86, Supplement 1. It is concluded that, to add safety margins to the plant safety analyses, component leakages can be used to determine the consequences of multiple leakages to ground on the DC system. Depending on the results derived from the analyses, circuit modifications can be made to reduce multiple leakages to ground and thereby protect the DC component from malfunctioning in a harsh environment.<>