Research On Harmonic Characteristics Of Series Arc Fault In Three Phase Load Circuits

In this paper,the series arc fault of three phase load is studied.Most of the series arc fault in three phase load circuits is single phase series arc fault,the two phase and three phase series arc fault is extremely rare,and the single phase series arc fault often occurs in the early stage.The characteristics of the three phase current signal in three phase load circuits are analyzed when single-phase series arc fault occurs.The harmonic characteristics of the single phase series arc fault in the three phase power system are extracted.Based on these characteristics,a feature criterion for diagnosing three phase load arc fault is constructed.This research has certain theoretical value and practical significance for safe and reliable operation of three phase power system.Firstly,the experimental device of series arc fault for three phase load is developed.Secondly,the experiment of single phase series arc fault experiment of two three phase asynchronous motors and two kinds of three phase frequency converters in different working state is carried out.The three phase current signal in the experiment is collected,the operation arc experiment and the load fluctuation experiment are carried out.Thirdly,an arbitrary subharmonic analysis method without phase lock loop based on the instantaneous reactive power theory is introduced,and the theory is compared with the FFT transform,wavelet transform,and empirical mode decomposition.Then,harmonic analysis of three phase current is carried out with FFT transform,and the harmonic characteristics of each load during normal operation and arc fault are analyzed.Due to the increase of the asymmetry and high-order harmonics in three phase currents when the three phase load has a single phase arc fault,the positive and negative sequence components of the fundamental and 2-13harmonics of the load current are extracted by the i_p-i_q without phase lock loop.After that,the amplitude change rate of the positive and negative sequence components of fundamental wave and each harmonic in the two adjacent power frequency periodic is taken as the characteristic attribute.Lastly,arc fault discrimination rules are constructed by decision tree.The interference signal is verified by operation arc signal and load fluctuation signal.The results show that the method can rapidly and accurately detect the single phase series arc fault in three phase power system.It can provides reference for series arc fault detection and recognition in three phase system.