【作者】 滕永禧；

【导师】 刘渝根；

【作者基本信息】 重庆大学 ， 电气工程， 2004， 硕士

【摘要】 接地网对变电站安全运行至关重要,但土壤的腐蚀可能使接地引线和水平均压导体变细甚至断裂,当系统发生接地故障时可能造成事故扩大,危及设备和人身安全。以往对地网的检测,一般只能采用测量接地电阻值的大小变化间接判断地网的腐蚀情况,或者大面积开挖检查接地网的腐蚀情况。这两种方法既不准确又带有很大的盲目性、工作量也极大,并且影响电力系统的正常运行。本文根据电路原理和故障诊断原理,提出一种新的接地网腐蚀诊断方法。该方法将接地网看成纯电阻网络,利用实际接地网的拓扑结构和接地引线间电阻的测量数据,应用特勒根定理建立接地网的腐蚀诊断方程,通过求解诊断方程得到接地网支路导体的变化值,进而判断接地网的腐蚀程度。本文就诊断方程建立的准确性、诊断方程的求解问题、测量方法的科学性以及提高诊断精度和减少测量工作量等问题进行了大量研究。并得出如下主要结论:由于建立的诊断方程是欠定和非线性的,本文采用数值迭代和非负最小二乘法相结合的方法求解方程,求解过程快速、诊断结果准确;提出现场测试中采用分步测量诊断方法,即初步测量次数按接地网总节点数的10%选择,然后根据初步诊断的结果再进行测量,这样大大减少了测量工作量避免了测量的盲目性又能保证诊断精度; 由于需测量的接地引线间电阻只有十几毫欧,因此现场测试时应选择直流双臂电桥,用四端钮连接法消除测量引线电阻和接触电阻的影响并消除现场电磁干扰;现场测试时测量点(接地引线)的选取对诊断结果有直接影响。因此测试区域应包括变压器中性点和避雷器接地引线以及易腐蚀区域。通过大量的仿真模拟计算、地网模型实验和实际变电站的现场试验,证明本诊断方法具有测试工作量少,诊断精度高,诊断快速等优点,能避免以往对地网检测的盲目性和不准确性,有着相当的工程实用价值。更多还原

【Abstract】 Grounding grid is essential to the safety of substation, however, the corrosion caused by earth may result in thinness even break of the grounding down-lead and horizontal equal-voltage conductor. This will lead to fault spread when grounding fault occurs, and will be dangerous to human and facilities. The obtain the corrosion level of grounding grid, two ways were always employed in the past, one was to measure and record the change of grounding resistance to evaluate the corrosion indirectly and the other was to dig widely to see the corrosion directly. These two ways are either inaccurate or aimless, they both need lots of work and affect the running of power system.A new grounding corrosion diagnosis method based on circuit theory and fault diagnosis theory is introduced in this thesis. This method regards grounding grid as a pure resistance network. The corrosion diagnosis functions are built in application of the law and then solved in use of the topology of real grounding grid and measured data of the resistance between down-leads. The result that will be used in the evaluation of the corrosion level is the change of the grounding grid branch conductance.In this thesis, the accuracy and solve of the diagnosis functions, the improvement of the diagnosis accuracy and the reduction of workload are researched. The main conclusions are listed below:(1) Because the diagnostic functions built are uncertain and nonlinear, so this paper adopt the method of numeric iteration integrated the minimum two-multiply to find the answer of the function, and the process of solution needs little time, the diagnostic outcome is accurate.(2) Putting up with the diagnostic method that measure step by step. The primary measured times are closed by the 10 percent of the whole nodes of the grounding network, then account to the result of the primary measure, make a farther measure. This can reduce the workload of measure, thereby avoid the blindness and also can insure the diagnostic precision.(3) Because the resistance between ground leads is only ten mΩ, The dc double bridge and four-port connection can cancel the effect of the measured wire and in the field contact resistance.(4) In the field, the election of measured nods (ground leads) has important effect <WP=6>on the result of diagnosis. So the measured region should include the ground leads of transformer and arrester.The emulation, experiment and field test indicate that this method has some merits: few measured work, high diagnosis accuracy and the rapid diagnosis speed. This method can avoid the blind test and the lack accuracy. So this method has correspondence engineering-utility value.更多还原