Approximate Approches For The Lightning-radiated Horizontal Electric Field In Time Domain And Induced Voltage On Overhead Lines

In modern society, the lightning electromagnetic pulse becomes more dangerous to power, communication systems and aviation field. Lightning horizontal electric field is one of the key parameters for the lightning electromagnetic coupling and damage effect. However, the proposed algorithms for computing the lightning horizontal field still have some drawbacks in accuracy and computation time. Therefore, it is very necessary to propose some more accurate and efficient algorithms.In the paper, we mainly do some research works about the lightning horizontal electric field in time domain and the revision of the estimation of lightning induced overvoltage peak. Firstly, based on the two-dimensional finite-difference time-domain (2-D FDTD) method, we have examined the accuracy of the time-domain method of lightning horizontal electric field (B-P approximate formula) and analyzed the lightning horizontal electric field under different cases with soil electric parameters. Secondly, we have extended the approximate formula of lightning induced overvoltage peak proposed by Paulino et al. to the case of the horizontally stratified ground and tested its accuracy by using the2-D finite-different time-domain method and Agrawal coupling model. The main results are as follows(1) Under horizontally stratified ground, the B-P approximate formula can approximately predict the horizontal field peak values with a satisfactory accuracy within errors of10%at distances from50to1000m from the lightning channel and the waveform predicted by B-P approximate formula is similar to that of2-D FDTD. However, in the vicinity of lightning channel (e.g.30m), the rise-time part of the wave predicted by the B-P approximate formula is similar to that of2-D FDTD, but its wave tail decays faster. The B-P approximate formula approximately has the same accuracy as that of C-R formula, because both of them are based on the surface impedance concept. When the soil conductivity a is larger than0.0001S/m, the effect of displacement current on the accuracy of B-P formula can be ignored.(2) Under horizontally stratified ground, when the upper layer has a lower conductivity than that of lower layer, the error of our extended formula for calculation induced overvoltage peak is dominantly less than10%for distances ranging from50to400m from the lightning channel. However, when the observation point locates400m from lightning channel and the upper layer depth is larger than5m, the error is larger than10%and our extended approximate formula has a much error. When the upper layer has higher conductivity than that of lower layer, the error of our extended formula is less than10%at distances ranging from50m to400m from the lightning channel.