Study On New Principle Of Fault Line Selection Adapted To Parameter Changes Of Small Current Grounding System

When the neutral point is grounded by the arc suppression coil,the residual current at the grounding point is small,but the voltage of the three-phase line of the system remains symmetrical,and the faulty line does not need to be cut off immediately,which greatly improves the reliability of the system.However,due to the compensation effect of the arc suppression coil,the capacitive current of the faulty line is reduced,and even the amplitude and direction of the steady-state signal of the faulty line are changed,so that the line selection method based on the steady state signal is not applicable,and these all increase the difficulty of line fault identification.If the faulty line cannot be found in time and the fault is eliminated,the fault range may be expanded,which may bring more serious safety hazards to the system.Therefore,new protection principles are proposed for fault line selection of the arc suppression coil grounding system.In this paper,through the transient steady-state analysis of single-phase grounding faults in small current grounding systems,three new methods for selecting small current grounding systems are proposed for different neutral grounding methods.The three methods are as follows:In order to solve the line Selection for Single-Phase Grounding Fault in Arc Suppression Coil Grounding System,a new method of line selection based on the phase difference between the zero-sequence admittance angle of the power frequency and the zero-sequence admittance angle of the characteristic frequency of the line is proposed in this paper.On the basis of analyzing the selected Frequency Band of the line,using the S-transform to extract DC amplitude information and the selected frequency band,The characteristic frequency of the zero-sequence current of the fault system is determined based on the principle of the maximum frequency point amplitude in the selected frequency band,and the characteristics of the zero sequence admittance vector under the line power frequency and the characteristic frequency are further analyzed.the fault line selection method based on the zero-sequence admittance angle of the power frequency and the zero-sequence admittance angle of the characteristic frequency difference is difference between the fault line and the normal line.In order to solve the problem of low accuracy of line selection with single phase angle information under high resistance faults,a fault line selection method based on the Amplitude phase measure(APM)and the Proportion of DC component-main frequency component(DCMP)is proposed in this paper.Firstly the transient zero-sequence current is decomposed into the attenuated DC component,the power frequency component and the attenuated transient main frequency component on the Prony algorithm.The fault line selection under the low fault closing angle is finished based on the comparison of the DCMP,because DC component in the fault line is much larger than the main frequency component in the fault line.The fault line selection under the high fault closing angle is finished based on the comparison of the APM,because the amplitude of the main frequency component in the fault line is much larger than that in the normal line,and the current phase is opposite to that in the normal line.In order to solve the fault Line Selection for Arc Suppression Coil Median Resistance Grounding System.A fault line selection method based on the power frequency increment coefficient is proposed for the fault line selection of the arc-suppression coil resistance grounding system.The equivalent circuit of the small current grounding system of the arc suppression coil resistance is analyzed firstly,The characteristics of the zero sequence current of the system under the grounding mode is analyzed,Based on the fault state,the current characteristics of the sequence are constructed,and a new principle of fault line selection based on K value is constructed.Finally,the value of the resistor and the input time is analyzed.The simulation results of the hybrid cable-overhead line system based on Matlab software show that the proposed line selection method is not influenced by the transition resistance and the fault closing angle.