Studying the Single-Phase Earth Fault Protection Based on Measuring the Negative-Sequence Current

The energy efficiency of the mineral resource complex enterprises depends directly on the reliability of power supply systems, which are physically implemented as extensive and highly branched distribution networks. To reduce economic losses from disconnections of distribution network electrical loads, a system of relay protection and automatic controls against single-phase earth faults is used. Under conditions of variable zero-sequence current and voltage parameters, this system must meet the requirements for modern protection systems. The article presents a study of the performance of protections based on measuring negative- and zero-sequence currents. The study is carried out using physical modeling and numerical analysis methods. The study results have shown that solid and arc single-phase earth faults give rise to both zero- and negative-sequence currents, with the negative sequence current appearing only in the faulty line. A device for protection against single-phase earth faults based on measuring the negative-sequence current has been developed. The use of the proposed device will make it possible to enhance the sensitivity and selectivity of non-directional current protections, ensure reliable operation of process equipment and critical consumers, decrease the level of electrical injuries of maintenance personnel, and reduce the economic losses associated with the repair of damaged electrical loads.