A Millman based alternate to symmetric component methods for fault level calculations in marine power systems

Abstract

This paper presents an approach to the calculation of unbalanced fault currents in shipboard power systems based on the application of Millman’s theorem. A full analysis of the time-variant fault current produced by a synchronous generator in a typical marine power system is provided; three phase three wire for principal loads and four wire earthed neutral for hotel loads. Hand calculation results obtained using a Millman’s theorem based approach are contrasted with results obtained by computer simulation and baselined against hand calculation results produced using conventional symmetric component methods. Results show that the Millman’s theorem based approach calculates fault levels that are broadly comparable to those produced using symmetric component methods. The Millman’s theorem based approach is however conceptually much simpler to apply than the conventional symmetric component method as it does not use the fictitious sequence components and networks employed by the symmetric component technique.