Identification of lightning strikes on transmission lines based on mathematical morphology and integral method

The transient signals generated by lightning strike may interfere with the travelling wave based equipments. The transient characteristic difference between the common fault and lighting strike is described in this paper. Using the characteristics of symmetric voltage waveform induced by lightning interference and that of asymmetric voltage waveform generated by fault within a very short interval, the waveforms of transient voltage above and below time-axes are integrated, respectively. Lightning interference and fault could be identified by comparing their relative ratio value of transient waveform. But in this method short-circuit faults and faults of lightning couldn´t be distinguished. Aiming at the problem, we analyze the energy spectra of voltage transient components by mathematical morphology, and found that short-circuit fault and most faults of lightning could be identified by the energy ratio of the relative low-frequency components and the relative high-frequency components. The PSCAD simulation results demonstrate that the proposed criterions are valid and correct.