Research On The Method Of Detecting The Magnetic Field Of Turn-to-turn Short Circuit Of Single-phase Air-core Reactor

As a significant component of the power system,the reactor has multiple functions such as reactive power compensation,filtering,and current limiting.Its healthy and stable working state is a prerequisite for the safe and reliable operation of the power system.In recent years,power accidents caused by reactor failures have become frequent,and the most common type of reactor in the power system is the air-core reactor.In order to improve the stability and reliability of the power system,efficient and feasible online reactor status monitoring technology is a scientific problem that needs to be tackled.At present,there are many methods for detecting the state of the reactor.The most commonly used method is to feed the reactor under test with a special waveform,a voltage of a voltage waveform of a specific frequency,and evaluate its status by analyzing the current signal flowing through the reactor.Although this method can distinguish obvious turn-to-turn short-circuit conditions to a certain extent,and even locate the fault point,it requires a power-off operation,the diagnosis system is complicated,the cost is high,and the operation is complicated.This research aims at simple and efficient online monitoring of reactor status and proposes a reactor status detection method based on magnetic field analysis.The concrete contents include the following aspects:(1)Based on the current research status of air-core reactor fault detection methods at home and abroad,a reactor state detection method based on magnetic field analysis is proposed.Then after comparing two commonly used methods of magnetic field analysis,it is determined that the finite element analysis of the internal magnetic field of the reactor is adopted.(2)It is introduced that the equivalent circuit of the air-core reactor,the calculation principle of space magnetic field,and the basic theory of finite element analysis.It is also clarified the calculation methods of the inductance,current and magnetic field in each state of the air-core reactor,which lays a theory for the finite element modeling and magnetic field analysis basis.(3)It is analyzed that the changes of the inductance and magnetic field of the aircore reactor during normal operation and when inter-turn short circuits occur at different positions.Faults are set in different coils and different positions of the coils,the magnetic field distribution is obtained through finite element simulation,and the influence of the fault position on the internal magnetic field distribution of the reactor is analyzed,which are combined with the magnetic induction intensity changes in the axial and radial directions of the reactor to obtain different the law of the effect of the fault on the inductance and magnetic field of the reactor.(4)The distribution characteristics of the magnetic field inside the reactor are analyzed using the two-dimensional Fourier transform method.Through the twodimensional discrete Fourier transform,the amplitude characteristics of the magnetic field in the frequency domain during normal operation and inter-turn short-circuit faults at different locations are obtained.More information about the magnetic field can be obtained from the frequency domain dimension,which can assist the measurement and identification of the reactor state.(5)Build an experimental platform to verify the simulation results.Based on the simulation parameters,the experimental platform of magnetic field measurement based on Gauss meter is built.By analyzing the measured magnetic field of the experiment and comparing it with the simulation results,it can be obtained that the experimental results basically match with the simulation results.The results of this study show that different faults correspond to different magnetic field distributions and their spectral distributions,and the different spectral characteristics and characteristic quantities of the magnetic field at different faults are used as the basis for determining whether a turn-to-turn short circuit occurs in the reactor and obtaining fault location information and can lay the foundation for the subsequent reconstruction of the expression of the magnetic field using the distribution characteristics,so as to realize the online monitoring of the state of the hollow reactor.