雷电冲击下接地装置精确建模与反击过电压计算

Accurate Modeling of Grounding Device at Lightning Surge and Lightning Back-strike Overvoltage Calculation

利用傅里叶变换和矩量法计算了某实际接地装置的频域响应,进而通过矢量匹配法将离散的领域响应特性拟合成连续、精确、定量的s域有理数学表达式,再通过数学推演,构建了可直接用于ATP等电磁暂态计算程序计算的接地装置冲击等值电路。与CDEGS(用于电流分布、电磁场、接地、土壤结构分析的一款软件包)计算结果对比表明,本文构建的等值电路在不同幅值、不同波前时间的各种冲击电流激励下,均能获得较真实的时域冲击响应,克服了以往利用冲击电阻模型对雷电流波形进行分析时的缺陷,具有重要的工程实用价值。对某实际线路耐雷水平的计算表明,传统冲击电阻模型的计算结果过于乐观。

The impulse response of a typical ground device in fi＇equency domain is obtained hy Fourier transform and moment method. And then the impulse characteristies are described by a rational mathematieal expression in s-domain using vector fitting, which is conscious, accurate and quantitative. According to the expression, the equivalent circuit in time domain which can be used in the ATP-EMTP program directly is buih. Compared with the CDEGS, the responses in the time domain obtained in ATP by the equivalent circuit is much closer to the reality than by the impulse resistance model under the different excitations of impulse currents. In fact, the value of impulse resistance depends on the curve of the lightning current hut the equivalent circuit does not. The lightning back-fiashover performance of an actual UHV AC transmission line is calculated using both the models. Results indic, ate that the lightning back-flashover performance is significant positive when using the impulse resistance model.