【作者】 崔玲玲；

【导师】 李景丽；

【作者基本信息】 郑州大学 ， 电气工程（专业学位）， 2021， 硕士

【摘要】 500k V变电站作为电力系统主干电网中的重要节点,其安全稳定运行对系统有着重要意义。在变电站内,良好的接地具有十分重要的工程意义,一般接地网埋于地下,不易直接判断其状况。目前,工程实际通常采用接地线导通试验、接地阻抗试验间接推断和开挖检查直接判断两种方式。以上两种方式中,间接推断具有不准确性,直接开挖具有盲目性。为了更好地诊断变电站接地网的状况,国内外许多学者提出了多种诊断理论与方案设计,但多数仅针对220k V及以下的中小型网络,且与工程现场实际情况结合不够紧密。课题研究了一种更适用于500k V变电站实际接地网的诊断方法,提高了诊断的精确性和效率。该诊断方法以电网络理论为理论支撑,将实际变电站接地网近似化为纯电阻网络进行研究,运用故障诊断原理和特勒根定理,确定诊断特征值,构建故障诊断方程,利用接地网设计图和技术文件得到诊断所需的初值,利用接地导通试验获取诊断所需的实际值,通过计算支路电阻变化量来判断接地网实际状态。诊断方程的求解引入了迭代思想,利用最小二乘法解决工程实际中方程数远少于变量数的问题,最终得到满足规程精度要求的诊断结果。因上述数值计算过程较为复杂,为使整个诊断过程操作性更强,更适用于工程现场,采用MATLAB中的GUI编制故障诊断软件,构建可视化操作诊断平台,实现更简便的拓扑结构搭建、关联矩阵生成和故障诊断分析。为验证该诊断平台的准确性,采用ATPDraw仿真平台搭建500k V变电站接地网电网络结构图,设置模拟故障支路,并利用仿真平台提供的电流源和电压探针元件获取故障发生后的接地网实际支路电阻值,在诊断平台中进行模拟诊断。在仿真诊断过程中,对不同诊断取值方式进行探讨,分别进行大跨距诊断方案、自然分块诊断方案和固定参考点诊断方案,对比不同诊断方法对诊断效率和精度的影响,并结合工程现场,提出具有操作性的诊断建议:充分结合接地网历史运行情况和诊断目的初步确定诊断范围,对诊断范围进行合理分区,使用固定参考点法进行节点对测试,在减轻现场工作量的同时增加方程组个数,使用数值计算方法提高诊断的效率和精度。最后,将诊断平台与现阶段接地导通试验结合,提出了规范化试验要求,总结了具体的试验方法,对郑州某500k V变电站和平顶山某500k V变电站进行现场实测,准确发现了接地网故障,验证了诊断方法的实用性和准确性,提高了500k V变电站接地网故障诊断的效率和精度,达到了工程实际运用的标准。更多还原

【Abstract】 The 500 k V substation is an important node of the main power grid of the domestic power system,which connects the power grids of various cities and provinces to form a stable power grid architecture.Its safe and stable operation is of great significance to the stability of the power supply of the whole system.For substation,good grounding has very important engineering significance.However,it is difficult to detect the horizontal grounding electrode directly because it is buried underground.At present,in engineering practice,the grounding wire conduction test and grounding impedance test are often used to infer the state of the horizontal grounding pole or to conduct excavation inspection directly.In these two ways,the indirect test is inaccurate and the direct excavation inspection is blind.In order to better diagnose the condition of the underground horizontal grounding pole,many scholars at home and abroad have put forward a variety of diagnostic theories and scheme designs,but most of the research is aimed at the small and medium-sized network of 220 k V and below,and the actual situation is fully integrated in the engineering site.This paper focuses on the grounding diagnosis optimization of 500 k V substation.Based on the theory of electrical network,the diagnosis method will be developed and the actual substation grounding network will be approximated to a pure resistive network.Based on the fault diagnosis principle and telegen’s theorem,the corrosion diagnosis equation is constructed,the initial value required for diagnosis is obtained by using the ground grid design Drawing and technical documents,the actual value is obtained by using the ground conduction test,and the branch state of the ground grid is judged by comparing the difference of the initial value.The method of least square method is used to solve the problem that the number of equations is far less than the number of variables in engineering practice.The above calculation process is relatively complex,will use MATLAB to complete.In order to make the whole diagnosis process more operable and applicable to the project site,the fault diagnosis software was compiled by using the GUI in MATLAB,and the visual operation interface was built to realize a simpler topology construction,correlation matrix generation and fault diagnosis analysis.The accuracy of the diagnostic software is verified by simulation test based on the actual substation grounding grid.ATPDraw program in ATP was used to build the actual substation grounding grid structure diagram,set fault parameters,and use the current source and voltage probe in the program to obtain the actual resistance value of the grounding grid after the fault,which was simulated in the diagnosis software.Model to explore the diagnostic approaches,in the diagnosis for large span diagnosis scheme,natural block,diagnosis and diagnosis according to the voltage grade,compare the different approaches to influence on diagnosis accuracy and efficiency,and connecting with the engineering site,the diagnosis could be operated suggestions: according to a preliminary analysis of grounding systems located in soil,diagnostic localization diagnosis for local grounding network,using the natural block or are rated according to the voltage value diagnosis method combined with large span,gradually close to the real failure.Combines diagnostic software and grounding conduction testing at present stage,summarizes the specific test methods,formed the standardized operation process,to the west of Zhengzhou 500 k V substation and the south of Pingdingshan 500 k V substation field measurement,accurate discovered,proved the practicability of diagnostic methods and accuracy,improve the 500 k V substation ground network efficiency and accuracy of fault diagnosis,reach the standard of the engineering practical application.更多还原