Fault Location Method For Hybrid Lines In Distribution Network Based On Improved Elephant Herding Optimization

Due to the needs of urban modernization,a large number of cables have been put into use,which has gradually increased the proportion of hybrid lines in the distribution network.A large number of discontinuous points of wave impedance make the fault traveling wave signal weak and difficult to be detected after propagating along the distribution line,and the wave speed of traveling wave varies greatly in different types of lines,which makes the traditional traveling wave localization method difficult to apply.Therefore,this paper proposes a fault location method for hybrid lines in distribution network based on improved elephant herding optimization.Firstly,based on the basic theory of traveling wave,the propagation characteristics of fault traveling wave at the connection point and branch node of hybrid line in distribution network are analyzed,and the propagation coefficients,line modulus parameters and modulus wave velocity of ground-mode and aerial-mode components of traveling wave are deduced and analyzed in detail.According to the propagation characteristics of fault traveling wave and the structural characteristics of distribution network,the initial traveling wave arrival time information obtained by each terminal traveling wave detection device is analyzed,and the difference matrix of multi terminal traveling wave information in distribution network is constructed.Based on this,the uniqueness of multi terminal traveling wave information is analyzed.Then,aiming at the problem that the fault traveling wave signal in the distribution network is weak and difficult to be detected effectively,a fault traveling wave detection method based on VMD-WVD is proposed.The aerial-mode traveling wave signal is decomposed by VMD(Variable Mode Decomposition),and the WVD(Wigner Ville Distribution,WVD)of each component signal is calculated respectively.The WVD of each component signal is superimposed to obtain the WVD of the original signal,thereby solving the influence of WVD cross term.The good time-frequency aggregation of WVD is used to extract the time information of initial traveling wave,and the simulation comparison experiment is carried out.Finally,a fault location method of hybrid lines in distribution network based on improved elephant herding optimization is proposed.The first step is to construct the fault location model based on the uniqueness of multi terminal traveling wave information in distribution network,and the fault location problem is transformed into an optimization problem,which does not need to preset the traveling wave velocity,and eliminates the influence of the difference of wave velocity of different line types.After that,the bad data with time synchronization error is eliminated by using the the OPTICS(Ordering Points To Identify the Clustering Structure,OPTICS)algorithm,and the fault location model is solved by using the improved elephant herding optimization algorithm to obtain the accurate location of the fault point.Ultimately,a large number of simulation experiments are carried out under the conditions of different fault types,initial phase angle,transition resistance,time synchronization error and detection error.The simulation results show that the traveling wave detection method proposed in this paper can accurately extract the initial traveling wave arrival time,which has obvious advantages compared with other traditional detection methods.At the same time,under different fault scenarios,the location method in this paper can achieve more accurate fault location,which has the characteristics of high reliability and strong robustness.