Research On Fault Location Of Transmission Line Based On Improved Hilbert-Huang Transform And Petri Net

It is very important to find the fault point and deal with it quickly and accurately after the transmission line failure.The traveling wave signal moving to both ends will be generated when the line breaks down and transmitted to each substation along the transmission line.The fault location can be realized through the analysis of the traveling wave signal received.For double transmission lines and contains branch multi-terminal transmission line fault location problem(T-type line),the application of classical Hilbert Huang transform(HHT)and the Petri net model of classic,positioning speed is slow,and positioning accuracy is not high.Therefore,this paper puts forward the improved Hilbert-Huang transform and Petri net method of transmission line fault location.Firstly,for double-ended transmission lines,the Hilbert-Huang transform(HHT)has the end-point effect and frequency mixing phenomenon,and there is overshooting or undershooting in the fitting process,and an improved Hilbert-Huang transform method is proposed.In the EMD process,the cubic Hermite interpolation method was used to replace the cubic spline interpolation method,and the overshoot and undershoot problems in the envelope fitting were avoided.Then,the first decomposed IMF was modified Hilbert transform,and the timefrequency diagram of the signal was obtained.From the time-frequency diagram,the arrival time of the wavehead could be identified.Then,for multi-terminal transmission lines(T-type lines)with branches,fault branches must be selected first.Aiming at the problem of the long time for fault location of ordinary Petri net model,the improved Petri net model is proposed.By using the information of circuit breaker tripping and protection action provided by SCADA system,the correlation matrix is reduced and fault branch can be identified more quickly.Then,the improved Hilbert-Huang(HHT)transformation algorithm is used to identify the arrival time of the wave at both ends of the branch,calculate the travel wave velocity according to the line parameters,and then calculate the fault location according to the traveling wave ranging principle at both ends.Finally,the simulation distance measurement is carried out for double-terminal transmission lines and multi-terminal transmission lines(T-type lines)with branches.Simulation results show that the improved HHT algorithm improves the speed and accuracy of fault location for double-terminal transmission lines.For multi-terminal transmission lines with branches(such as T-type branch),the improved Petri net model and the improved HilbertHuang transformation algorithm can more accurately determine the fault branch and fault time,which greatly improves the fault positioning accuracy of the transmission network.