【作者】 王树奇；

【导师】 刘健；

【作者基本信息】 西安科技大学 ， 安全技术及工程， 2009， 博士

【摘要】 为了对接地网的导体支路进行腐蚀故障诊断,及时发现接地网的缺陷,确保人身安全、设备安全、电力系统安全和生产安全,本文开展了下列工作:提出了接地网的分层约简模型,根据接地网的拓扑结构和可及节点分布,将接地网分为实际接地网、元版块网、可及接地网和本征接地网等4个层次,能够清楚地反映腐蚀故障诊断中不确定性发生的原因和所影响的范围,为判断接地网支路的可测性和进行故障诊断奠定基础。提出了一系列自动生成接地网的分层约简模型的新算法,包括准元版块分解算法、元版块分解和元版块网生成算法、元网络分解和可及接地网生成算法以及本征接地网生成算法,并建议了一种适合于接地网的分层约简模型的数据结构。将接地网支路定义为电阻可以唯一确定的明晰支路和电阻不能唯一确定的不确定支路两类,基于分层约简模型,提出了一种在充分测试方案下,采用规则和数值方法相结合的接地网支路诊断前可测性判断方法和流程,根据支路腐蚀状态提出了诊断后可测性的转化规则,结合实例深入论证了提出方法的必要性和可行性。提出了一种基于分层约简模型的接地网故障诊断方法,能够得出明晰支路的实际电阻,并以不确定支路组为单位,分别估计出各条不确定支路电阻的可能取值范围及其概率分布。在此基础上,提出了计算不确定支路、不确定支路组和接地网的信息熵的方法,从而对不确定支路的不确定程度和接地网的诊断效果进行了客观评价。探讨了接地网故障诊断测试方案的选取问题。提出并证明了最大电压定理的3个推论,指出在量测位置给定的条件下,若要使量测电压对某条支路电阻的变化最敏感,则激励电流源必须加在该支路上;当激励电流源加在某条支路上时,该支路两端电压对该支路电阻的变化最敏感。在此基础上,提出了一种抗干扰性强的最优测试方案,并针对接地引下线自身电阻影响的实际问题,讨论了解决方案。在一个60支路实验接地网上以及330kV沣河变电站的实际大型接地网上进行了可测性分析、腐蚀故障诊断和信息熵评价,诊断结果表明本文理论和所提出的方法是正确的和可行的。更多还原

【Abstract】 In order to diagnose the corrosion of the grounding grids, find out the defects in time and ensure the safty of power apparatus, electric power system and the personal safty, the following contributions have been made:A hierarchical simplification model for grounding grids is proposed. According to the topology and the distribution of touchable nodes, a grounding grid is simplified into four levels,such as Actual Grounding Grid (AGG)、Circuit Blocks Grid (CBG)、Touchable Grounding Grid (TGG) and Intrinsic Grounding Grid (IGG). The model can clearly reflect the reasons of uncertainty and the influencing ranges in corrosion diagnosis of the grounding grids. It forms the foundation of the testability evaluation and corrosion diagnosis of grounding grids.A series of novel algorithms are proposed to establish the hierarchical simplification model automatically,including the Quasi-Circuit Block dividing algorithm, the Circuit Block dividing and CBG generating algorithm, the Block Grid dividing and TGG generating algorithm and the IGG generating algorithm. The date structure which is appropriate for the proposed hierarchical simplification model of grounding grids is suggested.The branches of a grounding grid are classified into two kinds such as clear branches and uncertain branches. The resistance of a clear branch is unique whereas the resistance of an uncertain branch is not unique. A hybrid approach based on the rules and numerical methodology to evaluate the testability of branches of a grounding grid is proposed while the testing scheme is complete. The rules of transforming some uncertain branches into clear branches after diagnosis are analysed. The necessity and feasibility of the proposed approach are discussed with examples.A novel approach is presented to diagnose the corrosion of a grounding grid based on the hierarchical simplification model. The actual resistances of clear branches are obtained. The possibility resistance ranges and the corresponding probability distribution of uncertain branches are estimated within one uncertain branch group by another. The entropies of the uncertain branches, the uncertain branch groups and the grounding grid are formulated. Consequently, the uncertain degrees of the uncertain branches and the effectiveness of the diagnosis can be evaluated objectively.To determine the testing scheme for corrosion diagnosis of a grounding grid, three inferences of maximum voltage theorem are put forward and proved. It is pointed out that to make the measured voltage most sensitive to the change of resistance of a certain branch, the constant DC current exciter should be added on the corresponding branch. It is also pointed out that in case of the constant DC current exciter added on a branch, the voltage on the branch is the most sensitive to the change of resistance of the branch. Based on above theory, the theoretical best testing scheme is proposed. To avoid the influence of lead line resistances in the practice, some solutions are suggested.Based on the proposed model and approach, an experimental grounding grid with sixty branches and the grounding grid of Fenghe 330kV Substation are tested and diagnosed, respectively. The diagnose results show that the proposed approaches and algorithms are correct and feasible.更多还原