接地装置冲击特性研究分析

为研究接地装置的雷电冲击特性,以火花效应和电感效应的研究为主线探讨了土壤的放电特性、接地装置的高频响应及土壤电气参数的变化规律;比较了电路理论、电磁场理论以及动态建模等3种暂态建模方法;评析了目前接地装置冲击试验的进展。通过归纳与分析,指出了这一研究领域中迫切需要解决的技术问题及初步解决方法:利用X射线胶片或高速成像仪器采集土壤放电图像以研究土壤的放电形式及放电区域的尺寸;确定土壤的临界击穿场强及残余电阻率,并用于暂态建模中;区分火花效应与土壤电气参数频变性以及火花效应与电感效应的影响范围;建议分别采用分布参数电路模型、集中参数电路模型、电磁场模型分析伸长接地体、复杂接地装置及接地装置的频域特征;采用高电压、大容量冲击电流试验系统研究高幅值、波前时间短的冲击电流作用下接地装置的冲击特性,并用于指导冲击接地电阻的现场实测。

Impulse Characteristic Analysis of Grounding Devices

In order to study the lightning impulse characteristics of grounding devices,the research on spark effect and inductance effect is taken as the principal line of this paper.Plus the feature of soil discharge,the high frequency response of grounding devices and the change regulation of soil electrical parameters are explored.Furthermore,three transient modeling methods which adopts circuit theory,electromagnetic field theory,and dynamic modeling respectively are compared.The development of impulse characteristic tests of grounding devices is also commented.Through summary and analysis of the researches,several important and imperative technical problems needed to be solved and their elementary solutions are presented.The discharge form of soil and the size of discharge area could be approached by collecting soil discharge image by adopting X-ray films or high speed imagers.It is necessary to determine the critical breakdown field-strength and the residual soil resistivity of discharge area which are used in the transient modeling.The spark effect influenced range and the frequency dependence of the spark effect and the inductance effect need to be discriminated.It is suggested to analyze the frequency characteristics of the extensive grounding bodies,the complex structure grounding devices and the grounding devices by adopting the distributed parameters model,the concentrated parameters model and the electromagnetic model respectively.The impulse characteristics of grounding devices which are excited by the impulse current with high amplitude and short front time could be gained by adopting the high voltage and capacity impulse current test systems,and then be used in the field measurement of the impulse grounding resistance.