Secondary arc current interruption in an unconventional MV distribution system: digital simulation and experimental test results

The authors present results of experimental tests performed to evaluate the self-extinction capability of arcs across rod gaps of insulators for insulated shield wire lines used in a novel medium voltage (MV) distribution system. The studies relate to the construction of a pilot line in Ghana for experimental application of a new principle for power supply to isolated villages, with low power absorption (50 to 200 kW), located along HV lines (161 to 220 kV), at a distance of up to 100 km from the closest HV/MV station at one end of the line. Research performed on two different 161 kV line configurations, without any fault on the HV line, is summarized. The secondary arc currents, induced mainly by the capacitive coupling with the phase conductors of the 161 kV line, for shield-wire lengths of around 100 km, are found to be about 2.5 Ap and 3.4 Ap for lines with one or two shield wires, respectively. The recovery voltage, namely that which occurs across the spark gaps after arc extinction, may attain 11.4 kVp and 17 kVp, again in the case of one or two shield wires. Tests have shown that the suspension insulators with protective arcing horns ensure extinction of the secondary arc.<
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