Management of Zero-Sequence Parameters for Earth Faults on the Power Receiver’s Side in IT-Type Networks

This study examines the behavior and control of zero-sequence parameters in IT-type electrical networks under conditions of capacitive insulation asymmetry and complex asymmetric faults on the power receiver side. Existing methods of zero-sequence analysis typically address either symmetrical network conditions or single-phase earth faults in isolation, and they often neglect the combined effects of conductor breakage, transient fault resistance, and capacitive unbalance. To overcome these limitations, this work develops an analytical model based on the general theory of electrical engineering and symmetrical components, enabling a unified description of zero-sequence voltages and currents that incorporates both insulation asymmetry and compound fault scenarios. The model establishes closed-form relationships linking zero-sequence quantities to network parameters, power receiver characteristics, and transient resistances at the fault point. The results demonstrate several previously unreported effects, including a 180° vector shift and nearly 50% reduction in zero-sequence voltage and current magnitudes during simultaneous conductor breakage and earth faults compared with conventional single-phase faults—phenomena that critically influence the correct setting of protection devices. The study further shows that capacitive insulation asymmetry alone may generate zero-sequence voltages sufficient to trigger earth-fault protection regardless of the neutral grounding mode. These findings reveal increased risks of fault escalation, misoperation of existing protection systems, and prolonged unsafe touch voltages. Overall, the derived dependencies provide a new analytical basis for improving the design and coordination of protection systems in IT-type networks.