Using the Clarke transform for protection against single-phase-to-ground faults

RELEVANCE. Single-phase-to-ground faults remain one of the most common types of damage in distribution networks with isolated neutral. Arc-ing, intermittent single-phase-to-ground faults pose a serious threat to the power system's electrical equipment due to the transient processes occurring in the network during such faults. The prolonged flow of single-phase-to-ground fault currents in a cable line causes heating and can lead to a phase-to-phase short circuit. The development of high-speed and selective relay protection will prevent damage and ensure a reliable power supply to consumers. PURPOSE. To improve protection speed, the Clarke transform is applied, which combines the instantaneous values of the three phase currents to obtain an informational feature of a fault. It is necessary to develop a starting unit for single-phase-to-ground fault protection using the Clarke transform and to determine the properties of the resulting starting unit. METHODS. The Matlab software suite with the Simulink extension package was used for simulation modeling of current oscillograms under various operating conditions of an electrical network with an isolated neutral. The simulation results allowed for the development of a protection starting unit that utilizes the Clarke transform and features increased speed. RESULTS. A simplified structural and functional diagram of a starting unit for protection against single-phase-to-ground faults has been developed. A comparative sensitivity assessment was conducted with relay protection currently used in networks. The sensitivity of the developed protection unit during arc-ing intermittent single-phase-to-ground faults exceeds that of existing similar technical solutions. CONCLUSIONS. The research results are promising for creating new protection against single-phase-to-ground faults in networks with an isolated neutral, utilizing the Clarke transform.

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