Insulation Coordination Considering the Switching Overvoltage Waveshape—Part I: Methodology

A new insulation coordination procedure for switching overvoltages is presented. Based on the results of experiments, it considers the effect of the waveshape of impulses on the air gap strength, especially the impact of the time to crest and existing bumps above the continuous leader inception level. Signal-processing tools are applied to simulated overvoltage waveforms in order to extract their parameters which influence the insulation strength; the risk of failure of the transmission system is then derived. The procedure contributes to the refinement of insulation coordination studies and transmission-line projects. Application and results are provided in the companion paper.