Fault Line Selection Method To Resonant Grounded Based On The Mathematical Morphology And The Generalized S-transform

With the continuous development of the grid, the safe operation of the powerdistribution networks has become the focus of attention. Any failure of the powersystem will inevitably lead to an unpredictable loss. How obtained informationaccurately processed and fault timely removed was the key of stable operation of grid.Besides, people have higher demand on the safe operation and supply reliability of thepower grid. When the power system failed, it requires workers to be able to accuratelylocate fault and recover stable operation of the grid with the fastest.First, the paper theoretically analyzed single-phase ground fault characteristicsconcerning small current grounding system with different ground patterns. The modelof small current grounding system was built by the method of MATLAB/Simulink. Itresearched and analyzed the stable and transient features of current with single-phaseground fault of resonator system. The simulation model was built up usedMATLAB/Simulink software. Based on the superiority of combined method ofmathematical morphology (MM) and generalized S transform (GST), it put forwardthe fault line selection means of small current single-phase ground. MathematicalMorphology was a novel nonlinear filtering technique and able to identify the featureof fringe and shape of the signal. Considering the signal characteristics of the powersystem to simplify the needs of program resources, a linear structural element wasselected. When filtered, it can not only eliminate the burr shape noise, but alsomaintained the signal shape well. Generalized S-Transform can be seen either as anextension of ideas of wavelet or short-time Fourier transform, and it had a better time-frequency resolution. Therefore, the method became the hot tools.The model of small current grounding system was built by the method ofMATLAB/Simulink, and procedures of fault line selection were the following ones:Firstly, the signal was filtered by Mathematical Morphological. Secondly, thegeneralized S transform was used to analyze fault signal to get the modulus frequencymatrix. Finally, then the energy of modulus frequency matrix characteristics was analyzed. It could select the fault line. Lots of simulation experiments indicated that:the line selection algorithms based on zero sequence current and fault phase currentwere little affected by the factors of grounding resistance, fault time, fault location andso on. And this method was simple and fast. It can achieve fault line selection ofdistribution network accurately under different working conditions.