Research On Single-phase Arc Grounding Fault Line Selection Technology In The Distribution Network

When the single-phase grounding fault occurs in the medium-voltage distribution network in China,it is accompanied with the arc phenomenon.Due to the highly nonlinear and time-varying characteristics of the arc,the single-phase ground fault zero-sequence signals will be severely distorted,resulting in a large number of harmonics.Zero-sequence signals distortion has a certain degree of influence on the existing signal analysis method to extract fault information,which brings serious consequences for single-phase arc ground fault line selection technology,and directly affects the accuracy and reliability of arc grounding line selection technology.For the above problems,the time domain analysis method of Kusters&Moore distorted power theory is proposed,according to the characteristics that zero sequence signals are distorted severely.When arc grounding occurs,the distorted zero sequence signals are orthogonally decomposed,and the distorted zero sequence current is decomposed into active current and inductive(capacitive)reactive current and corresponding residual current.The paper accurately extracts the characteristics of zero-sequence equivalent conductance and residual current of each feeder.Different from the traditional analysis method,the zero-sequence equivalent conductance extracted based on the Kusters&Moore decomposition method simultaneously reflects the fault information contained in the fundamental wave and harmonics.The residual current is an integrated harmonic current that reflects harmonic fault information in the zero sequence signals.The paper analyzes the distribution characteristics of zero-sequence equivalent conductance and residual current of fault line and sound line respectively,and concludes that the zero-sequence equivalent conductance of the faulty line is greater than the zero-sequence equivalent conductance of the the non-faulty line when arc grounding,and the two symbols are opposite;the residual current of the faulty line is greater than the residual current of the healthy line.Therefore,the zero-sequence equivalent conductance and residual current are used as the fault feature to realize the accurate location of the fault line.This method is suitable for the research of arc ground fault line selection technology.In the paper,a single-phase arc grounding fault model is established in the distribution network.By changing the neutral grounding method,the line structure,the arc length and other effects,a large number of simulation results show that the proposed fault line selection methods are more accurate and superior for arc grounding fault line selection.