Driving high surge currents into long cables: more begets less

Reality checks can and should be applied to proposals for characterizing the surge environment and application of surge protective devices (SPDs) to end-user, low-voltage power systems. One such check is the fact that driving a large current with steep front toward an SPD installed at the far end of a branch circuit cable could require such a high voltage that the connections at the near end of the cable will flashover, limiting the stress applied to the far-end SPD. Tests and numerical modeling were performed to support this thesis. The results of real-world measurements and modeling, presented in this paper, are in good agreement and validate each other. From that point on, the model allows parametric variations of power cable length and surge current amplitude and waveform, of which several examples are presented.