A Single-ended Traveling Wave Fault Location Method For Transmission Line Based On VMD And SDEO

With the development of the society and the economy,demands to energy increased greatly have been leading to the rapid development of modern power systems.The transmission line,as the carrier of electricity,is an important part of the operation of the power system.Transmission lines and poles in the wild environment for long-term often encounter the damage to the natural calamities such as flood,earthquake,wild wind,strike of thunderbolt,which may lead to failure.Fast and accurate fault location can effectively shorten the time of fault line inspection,reduce the burden of patrol line,and reduce the economic loss caused by line fault.In recent years,scholars have made great efforts to promote the application and improvement of fault location methods.The existing fault location scheme is mainly dependent on single side protection or recording device,which is limited by the principle of single end method,and the precision of distance measurement is not satisfactory.In view of the facts that the accuracy of the traditional traveling wave fault location method is limited to the uncertainty of wave velocity and the high sampling rate as well as the accurate detection of the arrival time of wave head,an improved fault location method based on variational modal decomposition(VMD)and symmetric difference energy operator(SDEO)is proposed in this paper.(1)The formula for A-type traveling wave fault location method is optimized.The traditional single terminal fault location is mainly based on the accurate arrival time of the initial traveling wave and the traveling wave from the fault point to the bus line respectively,to find the distance between the fault point and the measuring terminal.Usually,the reflected traveling wave from the end of the bus will disturb the judgment of the initial wave head.This algorithm takes full account of the use of reflected traveling waves from the remote bus to further calculate the fault location in a certain range of the transmission line.The formula of distance measuring is classified by detecting the arriving time of the first two and the first three wave heads respectively,the results of which can be used as the optimal value of the result obtained by traditional method.This algorithm makes full use of arrival time of the first transient traveling wave and the length of the transmission line,which eliminates the influence of the uncertainty of the wave velocity and the length of the line and thus can improve the precision of location.(2)The detection method of the arrival time of the wave head is improved.Considering that the number of IMF cannot set in the EMD method,the IMF is easy to be drowned in the noise background,the influence of end effect and other problems are easy to cause bad performance of decomposition,the variational mode decomposition algorithm is introduced.First,the modal component of current traveling wave is obtained by variational mode decomposition.Then the instantaneous energy mutation time of the selected modal component is detected by using the symmetric differential energy operator.The VMD method can still protect the local characteristics of the signal after the signal decomposition,which is beneficial to the feature extraction of the fault signal.Symmetric differential energy operator has excellent tracking signal singularity,which enables the algorithm to detect the instantaneous energy mutation time of the wave accurately at lower sampling rate.Finally,the error correction method of sampling points is used to correct the sampling points corresponding to the arrival time of the initial traveling wave,so as to locate the failure point accurately.(3)The prediction of the fault section is studied.The single-terminal fault location method adopted in this paper needs to select different formulas according to the locations of different fault points.The fault location is calculated by the arrival time and the polarity of the first three wave heads.Due to the above reason,this paper introduces the genetic algorithm to optimize the weights and thresholds of the neural network model,uses the intelligent algorithm to roughly calculate the location of the fault,and makes a preliminary judgment on the fault point,so as to accurately identify the reflected wave head,and then select the corresponding formula for calculation.The algorithm optimizes the results obtained by the traditional single-terminal fault location formula and guarantees the accuracy of the results.(4)This thesis studied the modeling simulation of the new A-type traveling wave fault location method in theory and practical aspect.The model of transmission line fault location method is modeled and simulated by EMTP and MATLAB simulation software.By changing the sampling rate,fault location,fault type,transition resistance,signal-to-noise ratio and other conditions,the result of fault location is obtained,and compared with the results obtained by wavelet analysis.Simulation results show that the accuracy of the proposed method is higher than that of the wavelet method,and it can save equipment cost and is suitable for engineering applications.