Air Arc Model Of Single-Phase Ground Fault In Distribution Network And Its Application

Small current grounding is widely used in medium voltage distribution network in China,and single-phase grounding fault is the most common cause of small current grounding system fault.Most of the single-phase grounding accidents in distribution network belong to arc grounding.The transient over-voltage caused by arc grounding fault is very harmful to the distribution network.Its unstable and unpredictable characteristics make the effect of protective measures limited.One of the important reasons is the uncertainty of arc combustion.The accurate description of the transient characteristics of air arc in distribution network and the establishment of air arc model suitable for different working conditions play an important role in the analysis of arc grounding over-voltage process and the evaluation of arc grounding over-voltage suppression measures.In view of the above problems,this paper studies the transient characteristics,mathematical model and application of single-phase ground fault arc in the distribution network by building a 10 k V distribution network arc ground fault simulation test platform.The main contents are as follows:(1)10k V ground fault simulation test platform is set up,and the single-phase arc grounding test under different ground capacitance and different ground resistance is carried out.The voltage and current data of air arc in distribution network are obtained,and the change rule of arc current zero rest time,arc voltage,arc resistance and harmonic component of arc current with ground capacitance and ground resistance is analyzed.(2)Based on the black box model of the arc,the Mayr model of the air arc is improved by using the measured arc characteristics,making its time characteristic parameter τMore in line with the actual physical process,a simulation circuit is built in PSCAD to simulate the model.The results show that the model can accurately describe the external characteristics of the arc,and has a higher accuracy than the existing literature model.(3)Based on the theory of power frequency arc extinction,the paper applies the arc black box model proposed in this paper to simulate and analyze the over-voltage of intermittent arc grounding at different reignition time and different grounding resistance,and simulates and analyzes the over-voltage under the condition of adding arc suppression coil and phase to phase capacitance,and obtains the regulation of arc grounding overvoltage under typical working conditions Effect of laws and control measures.