Research On Line Selection Technology For Online Operation Of Small Current Grounding System

With the development of power technology and the improvement of power users' requirements for power supply reliability,small-current grounding systems have become the main grounding form of distribution networks.When a single-phase ground fault occurs in this system,online fault selection is always a problem in the relay protection technology of the medium-voltage distribution network.Aiming at the problems of low reliability and poor sensitivity of fault line selection technology for online operation of small current system,a new line selection technology,In order to better adapt to the power system,three differential topological structures were constructed,and the principles and methods of line selection under the differential topological structure were studied.By introducing the compensation branch,the method realizes the difference between the zero-sequence current measurement values before and after the compensation branch,and identifies the fault according to the difference characteristics,which is used as the fault line selection criterion.Using Matlab to simulate and analyze the single-phase grounding fault of the small-current grounding system,and obtain the simulation waveforms of the system zero-sequence current and grounding fault current,analyze the main influencing factors of the single-phase grounding fault current,According to the safety regulations of the power system,analyze the best compensation method to meet the safety of the power system,at the same time,it is compared with several other common traditional line selection methods;The feasibility,validity,rapidity and versatility of the line selection criterion are verified through simulation experiments,in order to solve the problems of low efficiency of fault information processing and low reliability of fault information diagnosis during fault line selection in actual power systems.The final result shows that there is a clear difference between the differential eigenvalues of the faulty line and the non-faulty line,which can accurately and quickly identify the faulty line,and is more accurate and faster than other line selection methods;It is of great significance to reduce the impact of faults,improve power quality and reduce fault losses.