Research On Single-phase Grounding Fault Line Selection Of Distribution Network Based On Parallel Resistance Of Arc Suppression Coil

In recent years,with the increase of the scale and capacity of the distribution network,the proportion of cable lines has increased.When single-phase ground faults occur,the capacitance current at the fault point is also increasing,which is likely to cause arc grounding.In order to limit the grounding point current,neutral grounding via arc suppression coil is widely used in distribution network.When single-phase grounding fault occurs in the distribution network,the three-phase line voltage remains symmetrical,the system can continue to operate for a period of time,providing valuable time for fault selection and removal,which improves power supply reliability;When single-phase grounding fault occurs in the distribution network system,the relative ground voltage of the non-fault phase will rise.If an arc grounding occurs at the grounding point,2.5~3 times arc overvoltage may be generated,which threatens the insulation and safety of the distribution network system,and it is easy to extent the scope of the fault.Therefore,the fault line must be selected and removed as soon as possible.However,the system can continue to run for a period of time,providing valuable time for fault selection and removal,and enhancing the dependability of power supply.However,due to the small fault current at the single-phase ground fault,the residual current is smaller after arc suppression coil compensation,and the fault feature is not obvious,which greatly affects the fault line selection.In this paper,the arc suppression coil parallel resistance method is used for fault line selection,which realizes the unification of fault arc extinction and fault line selection.In the case of instantaneous grounding fault,the arc suppression coil can extinguish the arc by itself to eliminate the fault.If permanent single-phase grounding fault occurs,after the system passes through the transient transition process,the parallel resistance is put into operation.At this time,the line selection is not affected by the transient process.The parallel resistance generates a large active current component and flows through the fault line through the grounding point.The current is opposite to the zero-sequence voltage of the system,which can be used as a criterion to select the faulty line.The input of parallel resistance can also reduce the neutral displacement voltage,and reduce the recovery speed of fault phase voltage.After fault line is selected and fault is removed,the parallel resistance will not affect the neutral displacement voltage.Affected by the actual operating environment,line model and length of the distribution line,a fixed parallel resistance can not adapt to the fault selection of a line in various operating conditions.In order to meet the requirements of safety and line selection accuracy,the selected parallel resistance value can not make the fault point current too large,but also ensure that the line selection has obvious characteristics.this paper proposes a method of inputting adjustable parallel resistance,through theoretical analysis and combined with Simulink simulation experiments,choose 550?~650? parallel resistance is able to adapt to different operation fault line selection.This paper conduct simulation by arc suppression coil parallel resistance line selection model,the results show that after the parallel resistance is input,the zero-sequence current of the faulty line becomes larger,and is much larger than the non-faulty line.The zero-sequence voltage of the system is greatly reduced,and the neutral point offset voltage is also greatly reduced;And cutting the parallel resistor does not affect the neutral point voltage.Verification of the superiority of the arc-suppression coil parallel resistance line selection method in the single-phase ground fault line selection of distribution network.