2014 International Conference on Lightning Protection ( ICLP ) , Shanghai , China Varistor Coupling for Combination Wave Test of Surge Protective Devices

The waveform influencing characteristics by vasistor coupling of combination wave test waveforms of surge protective devices (SPD) is studied in this paper. EPCOS vavistors, with maximum operating voltages ranging between 130 V and 750 V, are adopted here in OrCAD/Pspice environment to analyze the influence of vavistor coupling on output characteristic of the combination wave generator in test levels of 0 to 20 kV. Obtained results show that, owing to the varistor coupling, reverse oscillation phenomena will arise in the open-circuit voltages. The peak value, the front time, and the tail time of both open-circuit voltage and short-circuit current will decrease, whereas the virtual impedance will increase. The lower the test level, or the higher the maximum operating voltage of the vavistor, the more serious this effect. Compared with the conventional capacitor coupling, the range of the voltage of power supply networks and the levels of combination wave test by varistor coupling have to be limited to a great extent. Varistor coupling for combination wave test of SPD should be only used in special cases and special test levels where there are no strict waveforms limitations. KeywordsCombination wave; coupling network; OrCAD/PSpice; surge protective device (SPD); vavistor.