Identification of Transmission Line Lightning based on HHT

Lightning groundwire or tower without fault, back striking, shielding failure without fault and shielding failure with fault are simulated and analyzed in this paper based on the electromagnetic transient simulation software of ATP-EMTP. The results show that the current waveform of lightning strikes the ground or tower without fault is generated by the coupling of lighting current from lighting groundwire and oscillates around the axis of the steady state. Back striking contains processes of couple and flashover, its current waveform has characteristics of reverse polarity pulse and sudden current drop. The current of shielding failure without fault is the lighting current. The current waveform of shielding failure with fault is characterized by the truncation. On this basis, the Hilbert Huang transform (HHT) was introduced to do further analysis of the simulation results. The solution of end effect is also proposed in this paper. And thus the marginal spectrum was obtained by dealing with the simulated current waveform of lightning stroke. Then, calculating the energy distribution in different frequency bands and normalizing them. Therefore, a method for recognizing 4 types of lightning stroke is proposed which is on the basis of the energy proportion in different frequency bands. In addition, a large number of simulations are conducted to verify the effectiveness of this method by changing the parameters of the lightning current, grounding resistance and lightning distance.