Modeling Of Partial Discharge And Analysis Of Discharge Characteristics In High Voltage Electrical Equipment

With the increase of energy demand,electric energy,as a clean and environmentally friendly secondary energy,plays an important role in the national economy and people’s life.As an indispensable part of power system,high voltage electrical equipment is the basis to ensure the normal operation of power system.However,a variety of faults may occur in the high-voltage electrical equipment,which will affect the safety and stability of the power system.Particularly,the fault probability of power equipment caused by partial discharge accounts for more than 50%.The majority of the researches on PD characteristics mainly use experimental methods to observe the phenomena of light and sound,but for different types of partial discharge,the observational research method have certain limitations,which cannot effectively describe the micro-initiation process of partial discharge.Therefore,in order to well know the partial discharge characteristics,this paper aims to study the modeling of air gap discharge and tip discharge and the characteristics of microscopic discharge.In this thesis,the finite element method is used to solve the electronic continuous equation,the ion continuous equation and the electric field Poisson equation.The variation law of the charged particles during the air gap discharge process and the discharge characteristics of the cylindrical gap under AC voltage and DC voltage are analyzed.Combined with numerical simulation,the phase characteristics of air-gap discharge cases were analyzed,and it was found that the discharge signals appeared in both positive and negative half cycles of power-frequency phase,showing a large and small cluster of positive and negative half waves,and the signal amplitude was small and scattered.A fluid dynamics model of tip discharge in transformer oil is established,and the development process of tip streamer discharge under pulse voltage is analyzed.The shape development,space charge density and spatial electric field distribution of streamer discharge with different pulse voltage amplitude,different discharge spacing,and different rising are obtained.Numerical results show that under the same discharge spacing,with the increase of the applied voltage amplitude,the average velocity of the flow development changes significantly.Under the same applied voltage,the space charge generation rate is inversely proportional to the tip discharge spacing.The steeper the rising pulse is,the faster the average discharge velocity is,and the larger the discharge radius is.At the same time,it can be seen from the changing law of the flow morphology under AC voltage that when the voltage is in the positive half axis,the electrons constantly migrate to the anode and finally disappear to the anode,while the positive charge gradually develops to the cathode away from the anode and finally forms the flow discharge channel.When the applied voltage is in the negative half axis,it is the opposite.Based on the above simulation and field cases,the phase characteristics of tip discharge are analyzed,which lays a foundation for further identifying partial discharge categories.