Maintaining system stability and power supply needs to have an efficient detection and fast elimination of faults on transmission lines by the protection system. In order to clear transient single-phase faults on HV and EHV transmission lines, involving electrical arcs, Single Phase Auto-reclosure (SPAR) has been pointed out as the most recommended device. However, SPARs cannot distinguish between transient and permanent faults. In the presented paper, a new algorithm has been proposed to tackle this issue, identifying transient and permanent faults, for the purpose of single pole auto-reclosing applications. In this method, the arc voltage amplitude has been calculated using voltage harmonics at the fault location. Provided that this amplitude is large enough, the transient fault state will be immediately declared, enabling the autoreclosure, otherwise the scheme deduces that a permanent fault is occurred and auto-reclosure will be blocked. To evaluate the accuracy of the proposed scheme, rigorous simulations have been performed considering a wide array of different conditions, including fault location, fault resistance and arc voltage gradient, where, in all cases, the highest reliability has been achieved.

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