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A high-impedance fault is generated when an overhead power line physically breaks and falls to the ground. Such faults are difficult to detect and locate in electric power systems because of the small currents and voltage drops involved, which cannot be detected by conventional protection. Furthermore, arcing accompanies high-impedance faults, resulting in fire hazard, damage to electrical equipment, and risk to human life. This article presents an analytical description of the interaction between the electric arc associated with high-impedance faults and a transmission line. A joint analytical solution to the wave equation for a transmission line and a non-linear equation of the arc model is found for the case of an arbitrary reflection coefficient at the substation end, and a methodology for high-impedance fault detection and localization is proposed. The developed model is validated by means of a comparison with measurements. The comparison demonstrates the accuracy and effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Many high-impedance ground faults (HIGFs) that happen in low-voltage (LV) systems often cause customer supply loss, fire, and human safety hazards. Traditional ground-fault protection is provided by the residual current circuit breaker (RCCB). The RCCB is usually employed in an analogue measuring circuit and often causes nuisance tripping due to capacitive leakage current and load-switching operations. It offers only ground fault protection to a certain extent and has difficulty in detecting HIGFs associated with a dielectric material defect. In this paper active power variation-based protection for HIGFs is developed, and a dissipation factor (DF)-based criterion for identifying load-switching operation is proposed. They are implemented by cross-correlation analysis between phase voltage and residual current in single-phase networks. A digital protection scheme is also designed. EMTP simulation results show that the new protection can remove the influences of capacitive leakage current and load-switching operations and is able to detect HIGFs and prevent electric shock with high sensitivity and robustness. [ABSTRACT FROM AUTHOR]