Finite difference time domain simulation of lightning transient electromagnetic fields on transmission lines

Lightning parameters measurement of the transmission lines is the foundation of lightning protection research. It plays an important role in supplying the original accurate data to study the lightning characteristics, analyzing the reason for lightning accidents, and designing the insulation of the transmission line. In this paper, the distribution of the lightning transient electromagnetic fields around the tower is simulated by the finite difference time domain (FDTD) method based on a model established with reference to an actual 500 kV transmission tower. The analysis of simulation is used to verify the feasibility of non-contact lightning current measurement based on the differential loop. The obtained results show that when lightning strikes the conductor, the waveforms of magnetic field obtained from the detection points are the same as the lightning current´s waveform, and the amplitude of the magnetic field intensity exhibits a stabile linear relationship with the lightning current. All the detection points located around the tower can completely get current waveform flowing on the transmission lines. Moreover, the amplitudes and the polarities of the waveform from the detection points have different characteristics when lightning strikes different conductor. Lastly, a new lightning fault pattern recognition method which can figure out the lightning fault phase accurately is established based on the online monitoring of lightning current on the transmission lines by the differential loop.