不同土壤环境条件下建立土壤电离动态模型的方法研究

In different experiments and studies developed by several researchers, it has been shown that the impulse behavior of the grounding system differs from the behavior at mains frequency. When the electric field in soil around the grounding system exceeds the soil critical electric field but less than the breakdown electric field, the nonlinear phenomena of soil conductivity could be observed obviously. During the time, the soil resistivity of the affected section of soil decreases, resulting in decrease of impulse impedance. Due to the different geographical and climatic conditions, the nonlinear properties of soil conductivity are different. Based on characteristics of soil, it is essential to build the soil ionization model in studying the grounding system performance and electromagnetic field distribution in different localities. Recent research shows that Liew dynamic model can be integrated with FDTD and achieve the excellent agreement between simulation and experiment. Therefore, the electromagnetic field in the process of soil ionization can be analyzed by combination FDTD and Liew dynamic model. Then, the influences of each parameter of Liew dynamic model on electromagnetic field in soil are analyzed with FDTD, and the obtaining methods of the critical electric field and the parameters of the model are proposed. Finally, the validation of the methods will be further verified by the experiments of several typical grounding bodies in high voltage experimental sand pool and natural soil fed by an ideal current generator. And then, the method to build the Liew dynamic model according to different soil environment will be obtained, which provided a more accurate analysis model for quantitative analysis of ground bodies lightning surge response performance in different regions and climatic conditions.

大量实验研究证明接地系统的冲击响应不同于工频电流情况下的响应，当土壤中的电场强度超过临界电场强度又未超过击穿场强时，土壤表现出明显的非线性现象，此时，土壤电阻率减小，导致冲击电阻减小。然而不同地理、气候条件下，同一土壤的非线性特性也大相径庭，因此针对不同环境建立相应的土壤电离模型分析接地体的冲击特性，对于研究不同环境下接地系统性能及地下电磁场分布都至关重要。本课题将从电磁场分析的角度出发，首先将计算电磁学中的时域有限差分方法结合土壤电离LIEW动态模型建立电磁场理论计算模型，研究各参数对土壤中电磁场的影响，再针对土壤临界电场强度和土壤电离LIEW动态模型参数的获取提出确定方法，最后通过几种典型接地体在高压实验用砂池及自然条件下的土壤的实验进行验证，从而建立完整的针对不同环境的LIEW动态模型的确定方法，为不同地区、气候条件下接地体冲击响应特性的量化分析提供更精确的分析模型。

大量实验研究证明接地系统的冲击响应不同于工频电流情况下的响应，当土壤中的电场强度超过临界电场强度又未超过击穿场强时，土壤表现出明显的非线性现象，此时，土壤电阻率减小，导致冲击电阻减小。然而不同地理、气候条件下，同一土壤的非线性特性也大相径庭，因此针对不同环境建立相应的土壤电离模型分析接地体的冲击特性，对于研究不同环境下接地系统性能及地下电磁场分布都至关重要。本课题从电磁场分析的角度出发，首先将计算电磁学中的时域有限差分方法结合土壤电离LIEW动态模型建立电磁场理论计算模型，针对土壤临界电场强度和土壤电离LIEW动态模型参数的获取提出了相应的确定方法，为不同地区、气候条件下接地体冲击响应特性的量化分析提供更精确的分析模型。.基于本项目的研究成果，依托973等相关项目的持续支持，本课题组将本项目研究成果应用于闪电袭击移动通信基站时的相关电磁效应的分析研究上，设计出一套全新的针对电子设备的防雷系统。