Experimental and analytical investigation on metal damage suffered from simulated lightning currents

The damage of two typical metal materials, Al alloy 3003 and steel alloy Q235 B, subjected to four representative lightning current components are investigated by laboratory and analytical studies to provide fundamental data for lightning protection. The four lightning components simulating the natural lightning consist of the first return stroke, the continuing current of interval stroke, the long continuing current, and the subsequent stroke, with amplitudes 200 k A, 8 k A,400 A, and 100 k A, respectively. The damage depth and area suffered from different lightning components are measured by the ultrasonic scanning system. And the temperature rise is measured by the thermal imaging camera. The results show that, for both Al 3003 and steel Q235 B, the first return stroke component results in the largest damage area with damage depth0.02 mm uttermost. The long continuing current component leads to the deepest damage depth of 3.3 mm for Al 3003 and much higher temperature rise than other components. The correlation analysis between damage results and lightning parameters indicates that the damage depth has a positive correlation with charge transfer. The damage area is mainly determined by the current amplitude and the temperature rise increases linearly with the charge transfer larger.

An optimized transmission line model of grounding electrodes under lightning currents

In this paper, an optimized transmission line model （OTL） for modeling transient behavior of grounding electrodes under lightning currents is presented. The soil ionization effect is considered in OTL, and all electromagnetic couplings between dif- ferent parts of grounding electrode are also considered by selecting the size of segment conductor properly and calculating the mutual coupling parameters between segment conductors accurately. Comparing with the traditional transmission line model, the optimized model can be used to accurately predict the effective length and transient potential rise （TPR） of grounding elec- trodes. Transient behaviors of grounding electrodes are simulated by OTL and the results are in good agreement with those of the electromagnetic model proposed by Grcev, and experiment results performed by Electricit6 de France and Geri. Further- more, non-uniform discharging phenomenon of grounding electrode under lightning current is discussed, and the effective lengths of horizontal grounding electrode under lightning currents are presented.

Estimation of Lightning-Generated NO_(x) in the Mainland of China Based on Cloud-to-Ground Lightning Location Data

Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study is to provide a reference for the accurate estimation of the total LNO_(x) in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018.The energy of each CG flash was based on the number of return strokes per CG flash,the peak current of each return stroke,and the assumed CG breakdown voltage.The energy of intracloud lightning(IC)was based on the estimated frequencies of IC and the assumed energy of each IC flash.Combining the energy of lightning and the number of nitric oxide(NO)molecules produced by unit energy(ρno),the total LNO_(x) production in the mainland of China was determined.The LNO_(x) in the mainland of China estimated in this study is in the range(0.157-0.321)×10^(9) kg per year[Tg(N)yr-1],which is on the high end of other scholars’works.Negative cloud-to-ground lightning(NCG)flashes produce the most moles of NO_(x),while positive cloud-to-ground lightning(PCG)flashes produce the least total moles of NO_(x).The breakdown voltage of PCG is greater than that of IC or NCG,while the latter has a greater output of LNO_(x).

Preliminary Study on the Influence of Communication Station on Lightning Strike Risk in Its Neighboring Region

The communication stations are more easily struck by lightning because of its special geographical position. We proved theoretically that communication station increased the frequency and intensity of lightning strike in its neighboring region, thereby causing the increasing of lightning disaster loss. As long as the emphasis is put on the correct understanding and reasonably taking measures including： draining, grounding, equipo- tential bonding and shielding, it can be completely ensured that building and equipment of communication base station and its neighboring region are safe.

Statistical Analysis on Lightning Characteristics in Hebei Province

By using monitoring data of lightning locating system in Hebei during 1999- 2010 and lightning disaster data in Hebei during 2002- 2010,temporal-spatial distribution characteristics of ground flash and lightning disaster in Hebei Province were analyzed. Annual,monthly and daily changes of ground flash,lightning current intensity and ground flash density in Hebei were analyzed,and we compared ground flash with lightning disaster distribution.