Numerical Simulation And Characteristic Study On Partial Discharge In A Dry Air Cavity With A Plasma Fluid Model

Partial discharge is an important factor leading to insulation degradation of electrical equipment.Partial discharge measurement is often used to analyze the health status of electrical insulation materials in high voltage equipment and to evaluate the service life of electrical equipment.Hence,understanding the partial discharge mechanism is of great significance for maintaining the safety of power systems.At present,researches on the mechanism of partial discharge mainly focus on experiments,and are mainly limited to study the development law of partial discharge through controlling experimental conditions simply.Affected by the randomness of partial discharge and limited by the number of experimental samples,the experimental data is less,and the statistical rule is often inaccurate,while the numerical simulation of partial discharge can make up for these limitations.In this paper,a new partial discharge model in a void is proposed to solve some defects in other partial discharge models.In order to provide a more accurate description of partial discharge behavior from the physicochemical point of view,the actual particle reactions in partial discharge are considered.The model is verified according to the experimental data in the literature and used to simulate the partial discharge activity in the air cavity.In order to reveal the development law of partial discharge in air cavity,explore the underlying physical mechanism of partial discharge,and study the influence of external parameters on discharge characteristics,this paper uses the method of combining numerical simulation and theoretical analysis to investigate them.The specific contents are as follows:(1)According to the experimental data of relevant literature,a partial discharge plasma fluid model containing the actual particle reactions is built based on COMSOL Multiphysics simulation software,and the simulation results and experimental data are compared in two different ways,so as to verify the effectiveness of the model.Firstly,the spatiotemporal evolution of spatial electrons in air cavity is described in detail,and the phenomena of partial strong discharge migration and current pulse oscillation in air cavity are explained.Secondly,the main reaction pathway of ion generation/disappearance and the contribution of different ions to surface charge accumulation are analyzed in detail,and the generation law of the main oxidative product of the dry air discharge-ozone is also obtained.(2)On the basis of the above partial discharge model,the influence of voltage amplitude and power frequency on partial discharge activity is mainly observed by changing the external discharge parameters.First of all,the discharge waveforms of the external application parameters are compared,and the reasons for the differences among discharge waveforms are analyzed.Secondly,the evolution trajectory of the peak phase of the main discharge,the peak of the air gap voltage and the peak of the air gap current with change of the applied parameters is deduced theoretically,and the guiding role of the derivation is confirmed by combining and comparing with the simulation.Finally,the evolution rules of the average electron density and dissipated power in space and time,the increment of ozone and discharge power in a certain period of time with the change of the applied parameters is obtained.(3)The influence of air gap thickness and air gap radius on partial discharge activity is mainly observed by changing the size of air gap.The evolution trajectory of relevant electrical parameters in(2)with change of air gap size is studied again.