A systematic approach for calculating short-circuit currents in electrical power systems for commercial vessels

Short circuit current calculation is essential and important for power protection system designs in marine vessels. In the past, ship building corporations have used an adept short-circuit current analysis for marine vessel electrical power systems. However, in recent years, environmental awareness and economical concerns have motivated ship end users to demand solutions for energy saving and emission reduction on future vessels. Recognizing this trend, the ship building industry has introduced power converter-connected generators and motors, as well as alternative maritime power (AMP), into the planning and design of modern commercial vessels, in order to reduce fuel and operation costs, as well as air pollution emissions while at berth. New methods have been devised for the emerging power equipment to accurately calculate the short-circuit currents, in order to determine proper ratings of protection devices. This paper proposes a systematic approach based on the IEC 61363-1 standard for evaluating short circuit currents at different points in electrical power systems for commercial vessels with AMP and power converter-connected electrical machinery during a fault condition. To facilitate the analysis, a computer-aided sheet analysis program with a friendly user interface is developed. Test results of two practical reefer container vessel power systems with a shaft generator and AMP are presented and used to demonstrate the effectiveness of the proposed method.