| Due to the complex structure of the power grid,it is of great significance to quickly and accurately find faulty line points,maintain the stability of the power system,and avoid economic losses.Location and distance measurement have always been inseparable when studying line faults,and have been widely studied.When the line fails,the fault point is not accurate because the fault line is not obvious.At present,in most cases,the fault point is determined manually after the fault occurs,which cannot satisfy people’s reasonable use of resources.Therefore,this paper proposes to use the combination of low-voltage pulse method and EMD to determine the fault point,and through the analysis of the waveform passing through the fault point to determine the location of the fault point.(1)This article first discusses cable fault types,current research status of location technology and the development history of traveling wave method.According to the requirements of his actual research,the low-voltage pulse reflection method is proposed as the basic method.It introduces the shortcomings of Fourier transform and leads to the application of wavelet transform and EMD in ranging,and points out that EMD has modal aliasing and it needs to be solved urgently.(2)Combining the spatial filtering algorithm and the method of modulus maximum can suppress the modal aliasing phenomenon caused by sudden events in the EMD process.Abrupt modal aliasing is used to determine the abnormal time section by the method of anti-aliasing combined with smoothness,and the abrupt section is eliminated by the spatial filtering denoising algorithm and the method of modulus maximum,so that the abrupt section is basically eliminated.Basically eliminate modal aliasing and improve the accuracy of EMD decomposition.Through reconstruction,it is basically the same as the original signal without contamination.In the cable line,there are such abrupt signals or test data records,errors that are not allowed by machine testing can be reconstructed by wavelet-based anti-aliasing method to optimize the waveform to remove the error of the abrupt event,and the error is obtained by EMD decomposition.The more accurate time value can be applied in fault cable location.(3)Build a single-type cable,a cable with joints,and a hybrid cable simulation model through PSCAD,and then use Matlab to process the data obtained by PSCAD.First,a single type of cable fault is located and analyzed,and the fault location is determined according to the short-circuit and open-circuit characteristics encountered by the pulse wave and then the cable propagation.Then,the joint smoothness method is used to remove sudden events and reconstruct the optimized waveform to complete the positioning;For cables with connectors,the reflected waveforms are determined according to the traveling wave theory;for the new and old hybrid cables,the wave speed cannot be determined due to the different characteristics of the cable itself.We analyze the propagation of pulse signals in the old and new cables.The wave velocity segmentation method is used for research,Furthermore,by improving the comparison between the EMD positioning result and the wavelet transform positioning result,the accuracy of EMD positioning is higher and the effect is better,which has certain application value.Figure [51] table[3] reference[71]... |
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