Reasearch On Key Problems Of Fault Monitoring System For HVDC Transmission Line

With the development of HVDC transmission lines,they shoulder the responsibility of safe and reliable operation of the power grid.Once the transmission system fails,it will bring different degrees of economic and safety problems to the lives of residents.Therefore,rapid and accurate fault positioning is needed to reduce the loss after the failure occurs.In order to improve the fault location accuracy and power supply reliability,the background of this topic in high-voltage direct current transmission system,design the circuit monitoring combined with a high accuracy wave head extraction algorithm of fault location scheme,locating methods are put forward based on all kinds of lightning fault type and simulation verification,all can realize fault location accurately,concrete research content is as follows:Firstly,the rigid errors affecting traditional traveling wave fault location,including the uncertainty of overhead line length,traveling wave velocity and traveling wave shape decay error,are studied under the simulation model of HVDC transmission system.According to the characteristics of long DC line,this paper puts forward the advantage and necessity of dividing the line into several ranging areas by placing multiple monitoring points.In addition,the fault interval selection theory is proposed under the background of multi-location interval.The traveling wave polarity information obtained from the monitoring points is used to calculate the traveling wave similarity parameters for accurate fault interval locking,and the fault interval location process of transmission lines based on multi-measurement points is proposed.Then,in order to reduce the soft error of the wave head extraction in the fault location algorithm,a wave head detection algorithm combining variational mode algorithm and energy operator is proposed to improve the precision of the wave head extraction.Combined with the advantages of multiple measuring points,the legal position formula of traveling wave is further optimized,and the interference problem of traveling wave velocity is eliminated.Compared with the traditional wavelet fault location in the simulation example,the results show that the positioning accuracy is higher.In addition,according to the actual situation of the engineering line,a suitable installation scheme of monitoring points is designed.Secondly,considering the large noise interference along the long transmission lines,this paper proposes a denoising algorithm of travelling wave with noise based on mathematical morphology.For DC fault current data,appropriate filter structure elements are designed.The simulation results show that even in the strong noise interference,after mathematical morphology filtering,it can still reflect a higher signal-to-noise ratio,and accurately realize the detection of travelling wave head containing noise.At the same time,for the lightning fault existing in the HVDC transmission system,the relative position judgment basis of non-flashover points around the strike point is put forward,and the simulation verifies with VMD-TEO that the positioning method proposed in this paper can accurately achieve the fault location under various lightning fault types.Finally,on the premise of improving the wave noise filtering and fault location algorithm,this paper built a perfect data interaction platform based on Lab VIEW image programming software,and realized the systematic process of fault monitoring.The process of wireless communication and data storage is simulated successfully.