Analysis of thermal response mechanism of lightning-struck soil considering nonlinear electro-thermal characteristics

Abstract:

In order to analyze the thermal effects of soil under lightning strikes and describe the thermal diffusion process caused by lightning strikes in soil, a lightning strike soil model is established based on the electro-thermal coupling theory in this work. The model, by considering the nonlinear electric-thermal characteristics of the soil, can reflect the thermal effect. The transient computation was performed to investigate the characteristics of lightning current and the influence of soil characteristic parameters on thermal effects. In addition, the difference between the nonlinear electrothermal characteristics model and the traditional model in simulating the response of the lightning strike soil was compared. Finally, the rationality of the model was validated by the field observation data from previous researchers. The results show that: the energy released instantaneously causes a sharp increase in temperature near the contact point when lightning strikes the ground. The thermal effect of the soil reaches a peak at around 30 μs after a lightning strike, and the temperature influence radius is less than 40 cm. Besides, the lightning current and soil characteristic parameters have a significant impact on the thermal effect of lightning strikes on soil. The peak value of a lightning current can affect the radius of the area near the lightning strike point that reaches the melting temperature. Different lightning waveforms can determine the speed of current change, thereby affecting the speed of dissemination and range of heat in the soil. Higher initial resistivity of the soil will increase the thermal effects caused by lightning strikes, and a larger specific heat capacity will increase the thermal stability of the soil. The results of the current work are expected to have important theoretical and practical significance for understanding and predicting the thermal response of lightning-struck soil, which can further be applied to guide the design of lightning protection and grounding systems to improve the safety of infrastructures.