考虑非线性电热特征的雷击土体热响应机理分析

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

关键词:  雷击土体  非线性电热特征  热效应  电热耦合  热响应机理

Key words:  lightning-struck soil  nonlinear electro-thermal characteristics  thermal effects  electro-thermal coupling  thermal response mechanism

摘要:

为分析雷电作用下土体的热效应,研究土体中雷击引起的热扩散过程,采用电热耦合理论,考虑土体非线性电热特征,建立一种能够反映热效应的雷击土体模型。通过瞬态计算探究雷电流特性和土体电热特征参数对热效应的影响,并比较非线性电热特征模型与传统模型在模拟雷击土体响应方面的差异,采用前人现场观测数据对模型的合理性进行验证。结果表明:当雷电击中地面时,瞬间释放的能量导致接触点附近的温度急剧升高,雷击后30 μs左右土体热效应达到峰值,温度影响半径小于40 cm；雷电流与土体特性参数对雷击土体热效应影响显著,雷电流峰值影响雷击点附近的熔化区域半径,不同雷电波形决定电流的变化速度,从而影响热量在土体中的传播速度和影响范围；较高的土体初始电阻率将增加雷击产生的热效应,较大的比热容会提高土体的热稳定性。研究结果对于理解和预测雷击土体的热响应具有重要的理论和实际意义,可用于指导防雷和接地系统的设计,提高基础设施的安全性。

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.