One-line Ground Fault Phenomena on an Ungrounded Electrical Distribution System at Vessels

Abstract

As a consequence of growing trend in size of an electric distribution system at vessels, the ground fault will become unable to disregard since one-line fault current becomes higher, and necessity of introducing some supervisory or protective method against the fault, which is higher graded than ever, will be increasing. This time, we had an opportunity to research the ground fault phenomena at vessels. We report the results here, in which we have established the theoretical formula for the fault and carried out the numerical calculations at 440V AC 60Hz system, then confirmed those values on a vessel field. This study was also established on the basis of some aforegoing papers on the similar titles but further provides some practical method for calculating one-line fault current by utilizing materials of installation records of distribution system of a vessel, which will be applicable generally to vessels of any kind. In order to realize it, electrostatic capacitance against an earth or a hull on cables and various electrical machines were regulated for each size. Then the total capacitance of the experimental ship was calculated in the identical charging condition of circuitry at test and compared with that measured. A result was obtained that those two values were within a small tolerance.