Fault Analysis Of Power Distribution Network And Application Of Flexible Grounding In County Area

The safety and economic operation of county distribution power network plays a vital role in the overall security of the power grid,and is the focus of the management and maintenance of the power industry.With the rapid development of social economy,the demand of electricity in production and life is increasing,and the scale of distribution power network is also expanding.Therefore,how to isolate the faults quickly,avoid further expansion of the blackout scope and reduce the losses caused by the faults is particularly important.The influences of different line faults in 10 kV distribution power network are different,and there are obvious differences in operation under different neutral grounding modes.With the rapid increase of capacitive current,the accident hazards caused by excessive current become more and more serious.Therefore,this paper makes the following research on how to choose and improve the grounding mode of neutral point in the system rationally:Firstly,several common fault types in county area are systematically expounded,and the causes of the faults are deeply analyzed according to the actual operation and maintenance situation.Through data collection and analysis,the frequency of grounding fault is the highest,and single-phase grounding fault accounts for the largest proportion.The neutral point grounding mode of distribution power network is closely related to single-phase grounding fault,so the study of neutral grounding mode is introduced.Secondly,data modeling,theoretical calculation and ATP software simulation of single-phase grounding fault operation under three grounding modes are carried out respectively.By comparing the data and waveform characteristics of voltage and current under three grounding modes,the advantages and problems of each mode are summarized.Then,by optimizing and integrating the advantages of the three grounding modes,the flexible grounding method is proposed,that is,to connect small resistors with flexible switching in the grounding mode without grounding or through arc suppression coil.Then the logic of flexible control is designed,and single-phase fault simulation is carried out under flexible grounding mode to verify its rationality and superiority.Finally,a substation(Hexian 35 kV Huangba Substation)is selected as an engineering example,and the flexible grounding mode is designed and put into use by means of the opportunity of reforming the whole substation.After analyzing the actual fault situation on the spot,the relevant operation experience and existing problems are summarized,which provide a theoretical basis for the later promotion and application.