| Under the background of carbon peaking and carbon neutrality,the vigorous development of clean energy has put forward higher requirements for safety and stability of electrical equipment.The insulation performance of electrical equipment is one of the main factors that determine its normal operation.As a commonly used insulating material,epoxy resin will be affected by various environmental factors during production or operation,resulting in insulation degradation.Insulation deterioration often leads to voids at the interface between epoxy resin and metal electrodes,which distorts space electric field and induces partial discharges.The occurrence of partial discharge will accelerate aging of insulating materials and reduce safety performance of electrical equipment.In this context,this paper carried out the research and analysis of influence mechanism of interfacial void defects on partial discharge of epoxy resin from both experiments and numerical calculations.The results obtained will be helpful for further research on partial discharge.In this paper,epoxy resin samples containing hemispherical interfacial void defects were prepared in the laboratory,and the situation of extremely inhomogeneous electric field was simulated.Partial discharge experiments were carried out by using the parallel pulse current method,and the partial discharge fingerprints,discharge initiation voltage and maximum discharge capacity of samples with different void radii were obtained.The results show that when the void radius increases,the partial discharge initiation voltage and the maximum discharge capacity of sample also increase,and the trend of the discharge capacity in the discharge fingerprint graph increases with the increase of voltage is more obvious;The influence of the initial voltage is due to the difference in electric field inhomogeneity of different sizes voids.The larger the void radius,the higher voltage required for the field strength at the electric field distortion to reach the initial field strength;the effect of the void radius on the discharge capacity can be Due to the linear increase of electron acceleration distance under the action of electric field,the exponential enhancement of impact ionization intensity results in a larger discharge capacity during discharge.In order to deeply understand microcosmic nature of partial discharge behavior.this paper established a numerical calculation model for epoxy resin samples with different void radii by coupling Poisson’s equation and photoionization equation on the basis of fluid model,and analyzed the movement of charged particles in partial discharge.The characteristics of the discharge capacity of different void radius models were compared with experimental values,and the influence of the secondary electron emission coefficient on numerical calculation of model was studied.The results show that the multiplication process of charged particles in space has obvious phases;the reason for the change of cloud map of number density distribution of charged particles were different in generation rate of corresponding particles in different positions in space,rather than the actual movement of particles;For the models with different radii,the discharge occurrence time advances with the increase of void radius;compared with the influence of radius on shape of the discharge pulse,the influence of secondary electron emission coefficient is more obvious.The increase of emission coefficient promotes the development of impact ionization in space.When the emission coefficient is small,the waveform is not a typical double-exponential discharge pulse.With the increase of emission coefficient,the discharge occurs earlier,the discharge pulse width becomes narrower,the peak value becomes larger,and the waveform becomes a double exponential discharge pulse. |
