| Currently,most insulation materials used in electrical equipment and electronic devices such as polyethylene(PE)and epoxy composite materials are polymers.As the performance of polymer insulation materials deteriorates over long-term use,surface charge increases significantly and the resulting electric field distortion will increase the risk of surface insulation failure.Ceramic materials,on the other hand,have good insulation performance,excellent temperature stability,and strong aging resistance.Therefore,they may be more suitable for use in high-voltage direct-current gasinsulated equipment under strong electrical fields and large temperature gradients than polymer insulation materials such as epoxy resin.Thus,it is crucial to carry out basic formulation selection and modification optimization research on existing ceramic materials and analyze the impact of their electrical conductivity characteristics on surface flashover as it has significant theoretical and engineering value.This paper begins by preparing silicon nitride and aluminum oxide ceramic materials with different concentrations of doped functional ions,characterizing their phase structure,observing their surface morphology,and analyzing the influence of doped functional ions on the ceramic phase structure.It also obtains microscopic dielectric parameters such as material volume and surface carrier concentration,charge injection,and conduction potential barrier,trap energy level,and density through volume conductivity testing and thermal stimulation depolarization current characteristics.Based on this,it analyzes the tuning effect of ion doping on the temperature stability of ceramic resistivity.It was found that the Y2O3/Si3N4 ceramic material formula system designed in this paper has a high resistivity of 2×1015 Ω·m or more,and the decrease in volume resistivity between 293 K and 353 K is less than 50%,proving that the excellent temperature stability γ(T)characteristic of the ceramic material can significantly improve the electric field distribution under temperature gradients in DC devices,and enhance insulation strength,providing a theoretical basis for the regulation of high-performance ceramic insulation material formulations.Then,this paper builds a surface charge measurement experimental platform with a linear response characteristic,focusing on the experimental research of surface charge accumulation characteristics of silicon nitride and aluminum oxide ceramic materials with different concentrations of doped functional ions under DC voltage.The influence of doped functional ions with different concentrations on surface charge accumulation is analyzed.It was found that for the Y2O3/Si3N4 formula system,the ceramic with a 6%Y2O3doping concentration showed a lower surface charge density,while for the BaTiO3/Al2O3 formula system,the ceramic with a 3%BaTiO3 doping concentration showed a lower surface charge density.Finally,this paper builds a surface flashover measurement experimental platform using a planar pointed electrode to carry out experimental research on the impact of silicon nitride and aluminum oxide ceramic materials with different concentrations of doped functional ions on surface flashover under DC voltage.The law of the influence of doped functional ions with different concentrations on ceramic material surface flashover is summarized.It was found that the conductivity barrier caused by the influence of functional ion doping concentration on ceramic grain boundary quantity and structure could affect the flashover voltage.Moreover,the increase in surface charge could aggravate the distortion of the surface electric field and provide more starting charges for sample surface current injection,resulting in a lower flashover voltage. |
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