Background. In distribution networks with a voltage of 6–10 kV operating with an isolated neutral, current protections based on monitoring the fundamental frequency component of the zero-sequence current are used for protection against single-phase earth faults (SPEF). The selectivity and stability of such protections are significantly affected by intense transient processes during arc intermittent SPEF. One of the promising areas to improve current protection against SPEF is to increase the selectivity and stability of their operation based on recognizing the types of earth faults using a multiparameter approach to implementing relay protection.
Materials and methods. To develop and study methods and algorithms to recognize types of earth faults in 6–10 kV networks with isolated neutral and to evaluate the efficiency of their application to improve the selectivity and stability of current protection against single-phase earth faults, simulation modeling in Matlab, SimPowerSystems and Simulink has been used. The configuration and parameters of the simulation models consider the key features of distribution cable and overhead networks with a voltage of 6–10 kV of industrial, urban, and agricultural power supply systems, determining the characteristics of steady-state and transient modes during single-phase earth faults.
Results. The principles of implementation and the scheme of multiparameter current protection against single-phase earth faults for 6–10 kV networks with isolated neutral have been developed. They ensure recognition of all considered types of earth faults (stable, arc intermittent faults and non-hazardous for the network arc faults) and the possibility of automatic selection of the most effective method of its operation (signal or trip action). Functional tests on simulation models have confirmed the efficiency of the developed algorithms of operation of multiparameter current protection for all considered types of single-phase earth faults in 6–10 kV networks with isolated neutral.
Conclusions. The developed technical solution implements multiparameter current protection against earth faults ensuring increased selectivity and stability of operation for all types of earth faults compared to traditional designs of current protection against this type of damage, continuity of operation not only for stable, but also for the most dangerous arc intermittent earth faults, as well as the ability to select the method of protection for these types of earth faults.