Research On Physical Simulation Of Neutral Ineffective Single-Phase Ground Fault

In the distribution network,the small current grounding fault line selection and location has not been very good to solve,so the study of small current grounding fault transient signal characteristics has never stopped.Due to the particularity of electric power system,few opportunities to field test,and it has a certain risk.Although using electronic simulation is convenient and flexible,but simulation results may not be entirely consistent with the actual operation.In order to meet the development needs of teaching research and product research,let the students and teachers can teach and research in a simulated real system,and improving the scientific research and practical ability,so it is necessary to build a physical simulation system can demonstrate small current grounding fault under different fault conditions.It also provide a test platform for product development,production and debugging.This paper presented a system design of the different fault conditions simulating applied to a small current ground fault test.First of all,it analyzes the impact of different fault conditions for small current grounding fault transient signal.Then for different fault conditions,it puts forward the corresponding control scheme respectively.In the design process,follow the principle of simple,economical,flexible and easy to operate,The CPU of the control system designed is SCM,and short-circuiting switch with an electromagnetic relay or TRIAC.The implementation process of controlling different fault initial angle including the zero crossing detection circuit,microcontroller development board,switch driving circuit and short circuit switches and other parts.For different transition resistance,we use a series resistor methods to achieve.For the short-circuit point,we set up short circuit interface at different positions of the feeder line in distribution network simulation system.Due to the complexity of field operation environment,vulnerable to harmonic interference or noise.Therefore,the hardware design also made a number of measures to prevent interference.Make the control system means access to the active distribution network static simulation system,complete the small current grounding fault tests under different fault conditions.And observing the transient zero sequence current waveforms under different conditions,the variation characteristics consistent with theoretical law.So the test results verify the feasibility of the small current grounding fault simulation test.