Research on Conductance of Air AC Arc in Medium Voltage Distribution Network

The circuit channels of medium-voltage distribution systems are complex. Under the influence of harsh weather conditions, natural aging and other factors, arc faults are prone to occur and thus cause fire accidents. At present, there is still a lack of measured data on the diameter of the medium voltage air AC arc discharge channel, and it is impossible to calculate macroscopic conductance through conductivity, making it impossible to connect the arc energy model used in engineering with the physical and chemical processes inside the arc. The fault arc current of the medium-voltage power system is small, the arc temperature is relatively low, and the arc plasma does not satisfy the local thermodynamic equilibrium state. This paper uses the Spitzer model, the Z&L model and the M&G model to calculate the conductivity of air arc plasma, and analyzes the impact of the deviation from the equilibrium state on the conductivity. Finally, the arc conductance was calculated from the measured arc channel diameter. Compared with the local thermodynamic equilibrium assumption, the arc conductance calculated using the local thermodynamic imbalance assumption was closer to the experimental measurement.