Research Of Cable Fault Location Based On Variational Mode Decomposition And Wigner-ville Distribution

As the growth of the cable in operation time,the failure rate increasing because of cable insulation aging and other factors,if not timely troubleshooting,will inevitably cause the additional economic losses.Travelling wave fault location technology is the principal means of cable fault location,but the influence of the cable structure and running environment,make this method has some technical problems.Aiming at the problem of traveling wave method,such as reflection wave extraction,wavehead detection and wave speed uncertainty problems,this paper put forward the improvement method then improve the accuracy of fault location.The main contents of the study include:(1)The existing method of power cable fault location as well as the related digital signal processing technology are expounded and analyzed,and the problems existing in the existing fault location techniques are summarized.Combined with the common structure of power cables,the types of common faults and the causes of their occurrence,the basic principles of A-type traveling wave method and the propagation characteristics of traveling wave in cable are studied.(2)Aiming at the problem that the fault wave head is difficult to be accurately identified during the process of cable fault location,this paper put forward a wavehead detection method based on the combination of VMD and WVD.In this paper,the VMD of known synthetic signal and simulated fault signal is carried out to verify its feasibility in wavehead recognition.The decomposition of the known synthetic signal is compared with the EMD method,the results show that the VMD method can suppress the modal aliasing more effectively than the EMD method.By constructing the simulation circuit in ATP-EMTP,the location results of the method are simulated under different fault distance,different fault types and different fault ground resistance.The results show that the wave head recognition method in this paper can more effectively identify the fault wave head,thereby improving the fault location accuracy.(3)Aiming at the problem that the uncertainty of wave speed as well as the reflected wave can not be recognized automatically,a kind of single-double-ended low-resistance ground fault location method is proposed.The method obtains the positioning formula independent of the wave velocity according to the arrival time of the initial traveling wave and the reflected wave of the fault point as well as the total length of the cable.According to the relationship between voltage reflection coefficient and voltage transmission coefficient at cable fault point,put forward an intelligently identify method for the reflection wave from fault point.Using the simulation model,the location results of the method are simulated under different fault distances and different grounding resistances,,and through the MATLAB platform show the positioning data,the location results show that the method can effectively improve the fault location precision.The results show that this method can accurately find the fault spot and improve the positioning accuracy.