Single-Pole Autoreclosure in uncompensated EHV AC mixed overhead-cable lines. A parametric time-domain analysis

The successful application of the Single-Pole Autoreclosure (SPAR) to Extra-High Voltage (EHV) overhead lines (OHLs), as well as to the overhead portion of EHV mixed cable-overhead lines (MLs), significantly improves system stability. SPAR success requires that the secondary arc self-extinguishes during the dead time: according to the literature, self-extinction times increase with the increase of both secondary arc current and recovery voltage. Steady-state analyses of EHV MLs not equipped with inductive shunt compensation showed larger secondary arc currents and smaller recovery voltages compared to OHLs. Since steady-state analyses cannot give indications on arc self-extinction times, transient studies are required to assess which of the above effects has a prevailing influence, i.e., whether SPAR in uncompensated MLs results hindered or facilitated. This paper presents a time-domain study of the SPAR cycle in an uncompensated 400 kV-50 Hz ML, making use of detailed ATP-EMTP line and fault arc models. A parametric study has been carried out, evaluating secondary arc current, extinction time and recovery voltage for different single-phase fault locations along the overhead section of the line. Transient simulation results point out to extinction times being shorter in MLs than in OHLs of the same total length.