Distributed Insulation Monitoring Strategy (DIMS) for High Stray Capacitance Systems

Climate change is a global phenomenon which is becoming increasingly concerning. International efforts, such as the Paris Agreement [1] lead to transport electrification initiatives. HYPOBATT [2], in marine sector, aims for the charger that will enable a full electric vessel to be a reality. These systems have great amounts of energy storage. Together with electric machinery, EMI filters and distribution grids usually can sum up to some mF capacitance to earth, becoming a problem when detecting faults to ground, and therefore, a safety issue. To detect earthing faults insulation monitoring devices (IMD) are used, but as of Jan. 2024, the commercial IMDs available are not able to make a good measurement at stray capacitances (CS) above 3000µF [3], and all the devices in the mF range have response times of >100s. A new Distributed Insulation Monitoring Strategy (DIMS) approach is proposed in this paper, with simulation results, to make a faster and more reliable measurement of earthing faults in isolated terra (IT) systems with stray capacitances in the range of the hundreds of µF. The impedance to ground is measured in isolated parts of the whole system and then a higher-level logic is implemented to compute a total safety status. Key words. Stray capacitance, modular insulation monitoring, IT systems, marine transport electrification, energy storage system.