电工技术学报2024，Vol.39Issue(7)：2046-2059,14.DOI:10.19595/j.cnki.1000-6753.tces.230065
基于动态电阻串联的高阻接地故障精确建模
Accurate Modeling of High Impedance Fault Based on Dynamic Impedance Series Connection
摘要
Abstract
High impedance fault(HIF)may occur in distribution lines owning to harsh weather condition,which is difficult to be detected due to its over thousands of ohms impedance,posing a huge hazard to human and electric equipment.Therefore,the safety risks and the lack of actual HIF data make it essential to require an accurate HIF model.However,only based on heat balance or dielectric breakdown theories,existing HIF models fail to capture nonlinear characteristics due to the insufficient physical interpretation of HIF.Thus,considering the entire fault physical process,a HIF model based on dynamic impedance in series is proposed.By comparing it with other models,the simulation results verify that the proposed model characterizes HIF nonlinear characteristics under various grounding media with higher accuracy. The HIF experiments under laterite soil had been carried out in the 1:1 real distribution network testing field.Based on the recorded waveforms,the HIF physical processes are analyzed,specifically including the arc ignition and extinction characteristics and the current dispersion in soil.The findings suggest that the nonlinearity of grounding medium and air breakdown process are the primary contributors to the nonlinear distortion of fault current waveforms.Correspondingly,it can be revealed that the HIF fault impedance is composed of arc impedance and ground impedance in series.On this basis,a new HIF model based on dynamic impedance in series is proposed.Firstly,the Thompson Theory is utilized to describe the arc ignition and extinction characteristics in air breakdown process,based on which the dynamic exponential arc impedance model can be established.Secondly,with the analysis of the fault current dispersion process,the variation curve of soil resistivity with electric field intensity is obtained,then the grounding impedance can be calculated to establish the grounding impedance model.Though the analysis of grounding impedance only takes laterite soil as an example,it is worth noting that this is just an approach to calculate grounding impedance,which is not limited by the types of grounding medium.In principle,the approach applies to all grounding media.Ultimately,the new HIF model is obtained by connecting these two impedance models in series.The new HIF model takes the entire HIF physical processes into consideration,featuring specific physical significance. To validate the effectiveness of the proposed HIF model,a large number of HIF simulations were carried out and the simulated waveforms were compared with the field experimental waveforms using waveform correlation coefficients.Firstly,the simulated waveforms and Voltage-Ampere characteristics curve are similar to the field testing recorded data.Furthermore,for HIF occurring under laterite soil,gravel,and micro sand,the fault current waveform correlation coefficients between simulated and real testing data are 0.976 2,0.969 3,and 0.965 8 respectively.The simulation results verified that the proposed model exhibits outstanding performance.Secondly,the fault current waveform correlation coefficient of proposed model reaches 0.976 2,compared with only up to 0.925ԝ6 for other existing HIF models.In other words,proposed model can better reflect the nonlinear distortion characteristics of HIF faults with higher accuracy,which demonstrates the superiority of proposed model. The following conclusions can be drawn from the theoretical and experimental analysis:(1)The real field HIF experiments indicate that the fault current waveform and volt-ampere characteristics curve exhibit obvious non-linear distortion,and the fault impedance fluctuates periodically.(2)The HIF physical process including air breakdown and soil current dispersion are analyzed.Correspondingly,the fault impedance can be composed of arc impedance and grounding impedance.On this basis,a new HIF model based on the dynamic arc and grounding impedance in series is proposed,which features characterizing HIF physical process.(3)The proposed model is constructed in PSCAD.Comparing it with field experiments and other HIF models,the simulation results verify that the proposed model can more accurately characterize the HIF nonlinear features under various grounding media,providing more precise HIF data for subsequence research.(4)However,the proposed HIF model has certain limitations due to the diversity of grounding media.Therefore,the upcoming research will focus on classifying these various grounding media,aiming at constructing a more accurate and comprehensive HIF model.关键词
配电网/高阻接地故障/电弧电阻/接地电阻/非线性特征Key words
Distribution network/high impedance fault/arc impedance/grounding impedance/nonlinear characteristics分类
信息技术与安全科学引用本文复制引用
钟逸涵,邓丰,史鸿飞,徐帆,李鑫瑜..基于动态电阻串联的高阻接地故障精确建模[J].电工技术学报,2024,39(7):2046-2059,14.基金项目
国家自然科学基金(52077008)、湖南省自然科学基金杰出青年项目(2022JJ10048)和湖南省湖湘青年科技创新人才项目(2021RC3097)资助. （52077008）
