Ground-Fault Recognition in Low-Voltage Ships Based on Variation Analysis of Phase-to-Ground Voltage and Neutral-Point Voltage

Generally, ships use a three-phase power system with low-voltage and ungrounded systems to ensure continuous power supply. In these shipboard power systems, ground faults constitute approximately 95% of all faults. Most ground faults are caused by the single line-to-ground fault. Ground faults can cause blackouts, which significantly impact the safe operation of ships. Therefore, ship engineers should identify the ground-fault region for effective management and resolution. This study analyzes the variations in the phase-to-ground voltage and neutral-point voltage during a ground fault in a distribution network of an ungrounded low-voltage ship. We proposed a practical method for ship engineers to determine the ground-fault phase by measuring only the phase-to-ground voltages. To verify the applicability of the practical method to real ships, the line-to-ground capacitance was directly measured for a 225 V power system of a training ship. Moreover, we performed simulations based on the measurement data and analyzed the variation characteristics of the phase-to-ground voltage and neutral-point voltage during a single line-to-ground fault. Thus, ship engineers can use the simulation results and proposed table to accurately determine ground faults by measuring only the phase-to-ground voltages.