Research Of Single Phase Grounding Fault Selection Based On Zero-sequence Energy Identification

In our country,the neutral point of distribution network is generally non-effective grounding,also known as small current grounding.When the single-phase grounding fault occurs,fault current is small,under this kind of grounding fault power system can run 1~2 hours improving power supply reliability.However,the disadvantage is that the identification information of fault is too weak to select the fault line with high accuracy.Because the correct selection rate of the single phase grounding fault of the distribution network is low,it is not conducive to the stable operation of the system,so it is of great significance to research the principle of ground selection of distribution network.This paper first analyzes the existing line selection methods of non-effective grounding systems both at home and abroad,and understands the limitations and deficiencies in the actual line selection.Secondly,through the analysis of the steady-state equivalent circuit when a single-phase high-resistance-to-ground fault occurs,the expressions of the zero-sequence voltage and the zero-sequence current in the line during high-resistance-to-ground fault are deduced.In the paper,frequency-doubling steady-state zero-sequence voltage and current are proposed and the frequency-doubling zero-sequence energy are selected as the criterion of line selection,which greatly improves the ability to identify fault identification information and reduce the influence of noise,so as to achieve the purpose of correct line selection.The theoretical analysis shows that the magnitude of the zero-sequence energy at the bus outlet of the faulty line and the rising speed of the waveform are greater than the zero-sequence energy at the outlet of the sound line.This method can correctly select lines for low resistance grounding,high resistance grounding,and arc grounding faults,improving the accuracy and sensitivity of line selection.Finally,the ATP-EMTP simulation software was used to build the distribution network model and the arc model to simulate the status of various faults.The simulation results were compared with the theoretical analysis to verify the correctness of the line selection method based on zero-sequence energy identification.