【作者】 翟绍思；

【导师】 梁贵书； 靳伟；

【作者基本信息】 华北电力大学 ， 电气工程， 2011， 硕士

【摘要】 雷电感应过电压是配网线路发生绝缘闪络的主要原因,其降低了供电可靠性,给人们生产与生活带来了严重影响,因此,实现雷电感应过电压的计算、预测架空线路的闪络概率并对雷电感应过电压防护措施进行研究具有重要的工程价值和实际意义。本文首先介绍了雷电感应过电压的产生机理,雷电感应过电压对输电线路的耐压水平等的重要性,并对雷电回击模型进行了阐述和总结。本文将雷电视为垂直于大地表面的电流通道,基于电磁场理论,利用雷电感应电磁场的近似计算公式,完成了考虑有损大地情况下的雷电感应电磁场的求解;并以所求电磁场为激励,结合Agrawal场线耦合模型,基于时域有限差分法(Finite Difference Time Domain, FDTD)推导了改进电报方程的时域递推差分形式,编写相应的计算程序,实现了配网架空线路的雷电感应过电压计算。通过对一段典型架空线路进行计算并与现有文献结果比较,验证了程序的正确性。利用所编写的计算程序,讨论了大地电阻率对雷电感应过电压的影响,得到了在雷电感应过电压计算中必须计及大地损耗的结论。此外,还探讨了配网线路雷电感应过电压闪络概率的计算方法,并讨论了避雷线的架设对线路闪络概率的影响,说明了在线路上方架设避雷线不仅可以减少直击雷害而且还可以有效降低感应雷导致的线路闪络,提高供电可靠性。更多还原

【Abstract】 LIGHTNING induced overvoltages may cause damage to the insulation of the distribution lines or other power equipments. Erksson et al. have evidenced that the indirect lightning return strokes, hitting the ground in the vicinity of overhead lines, constitute a more dangerous cause of damage than direct strikes, because of their more frequent occurrence. The research on the calculation of the lightning-induced overvoltages and prediction of the flashover of the distribution power system are very important for the insulation design of power lines.This paper introduces the mechanism of the lightning over-voltage, the importance of lightning induced over-voltage for the voltage level of the distribution overhead line. It assumes that the shape and speed of the lightning current remain the same with height while the amplitude is exponentially decay with the height. As the disadvantage of having a discontinuity at the stroke tip, which is presented in other models, is avoided. The Heidler model is chosen as the lighting base current model. Assuming the lightning channel as a vertical channel to the ground, the electromagnetic is calculated based on the Maxwell equation. The Agrawal model is chosen as the coupling of field-to-line model and the over-voltage induced by lightning strikes was calculated base on FDTD and Agrawal Model. Through a section of a typical calculation of overhead lines and compared with the existing literature, correctness of the method is verified.Discussion is implemented for the effects of the conductivity of the lossy ground to the lightning-induced overvoltages. Furthermore, the method about how to evaluate the flash over probability of the distribution system is presented and the discussion about the effects of the ground wire to the lightning-induced overvoltages is implemented, as a result, the equipment of the ground wire can reduce the overvoltages of the overhead lines and improve the quality of the distribution power system.更多还原