Research On Fault Location Method Based On Zero Sequence Current Integration And Improved HHT Transform

With the rapid rise in power consumption in the current power system,the grid structure has gradually become complicated.Finding fault points quickly and accurately is critical to ensuring safe and stable operation of the power system.Fault location have always been hot issues for experts to study.In this paper,the author focuses on the single-phase ground fault location of the distribution network and the traveling wave fault location of the transmission line.In the case of single-phase grounding fault,it is difficult to judge the fault point because of the small fault current,the obvious electrical quantity,the various operation modes and the complex structure of the system.At present,the main way to determine the fault point is manual patrol,which is not only time-consuming and laborious,but also difficult to find the fault location quickly and accurately.In this paper,the author uses the zero-sequence current flowing through the line before and after the single-phase ground fault location to have a large difference,and the zero-sequence current waveform flowing through the detection points on the front and rear sides of the fault end is large,and the zero-sequence current waveform on the same side line is similar.The author uses the zero-sequence current data in the two power frequency cycles after the faults on both sides of each section,calculates the amplitude in different time periods,uses the integral algorithm to obtain the amplitude integral coefficient,and finally judges the fault section according to the amplitude integral coefficient.In this method,only the zero-sequence current signal on the line is needed,and the signal acquisition is convenient;It only needs to upload the integral coefficient of the detection point’s amplitude,and the data transmission amount is small.Before transmission to the distribution network,it must be transmitted through the transmission line.The failure on the transmission line will affect the normal operation of the next distribution network.When the transmission line fails,it transmits the traveling wave signal to the substations along the way.At present,fault location methods are mainly carried out by wavelet transform,which requires artificial selection of wavelet basis.If the wave base is not self-adaptive,it will affect the fault accuracy.In this paper,the author introduces the Hilbert-Huang transform(HHT)method and proposes to apply the cubic triangular cardinal interpolation method to empirical mode decomposition(EMD)to suppress the overshoot and undershoot problems of the original interpolation,by which the fault location can be found more accurately.The EMD decomposition is performed on the traveling wave signal arriving at the measuring end of the fault point;The first IMF component obtained is improved by HHT transformation;The time-frequency diagram of the signal is obtained,the arrival time of the wave head is obtained from the amplified time-frequency diagram,and the fault distance is calculated by combining the previously determined wave velocity.The results show that the fault point ranging error is only 15 m in the case of AB two-phase fault.