Research On Fault Diagnosis For Grounding Grid In Substation Based On Tikhonov Regularized Principle

With the continuous development of power grid in China,EHV?high-capacity?long-distance transmission has become the mainstream of the development of modern power grid,besides,the large number of substation use of electronic automation equipment,making the system more demands on the substation grounding network.According to statistics,the annual accidents caused by grounding fault occur frequently,and that has brought great security risks to the electrical equipment and staff.And as the accident further development,it will cause serious economic losses and social impacts.Therefore,to find and deal with the fault of grounding grids timely and effectively are very important to ensure the safety of the electrical equipment and the staff.In order to achieve the premise without blackout and digging large area of grounding grid,this paper established a mathematical model of fault diagnosis of grounding grid,which based on the electric network theory and the principle of minimum energy distribution of grounding grid.Considering the underdetermined and ill conditioned properties of the equations in the model,a general least square algorithm based on the Tikhonov regularization principle is derived and proposed in this paper,and the corresponding diagnostic program is compiled by MATLAB software.Based on the existing research experience and test conditions in our research group,a large number of fault diagnosis of grounding grid?Chongqing 110 kV and 220 kV substation grounding grid were carried out.The results showed that the method can diagnose the fault of single branch quickly and accurately.When in multi branch fault diagnosis,the effect is still considerable,and all meet the error requirement of engineering.In the preliminary fault diagnosis of large grounding grid,this method fails to diagnose all faults,but the error decreases significantly,and diagnostic speed is faster after increasing the number of iterative equations by increasing the excitation and measurement of the node voltage.In addition,in the fault diagnosis of medium and large grounding faults,the regularization parameter ? decreases with the number of iterations(nonzero),it can be seen that the iterative solution converges to the exact solution.Compared with the traditional genetic algorithm,this method avoids the complexity of crossover and mutation to a certain extent,which is shorter and improves the diagnostic efficiency.