96 / 2018-08-24 15:55:29

Space Charge Simulation Based on Comsol

space charge,comsol,simulation

At present, high-voltage direct current transmission technology is more and more widely used in long-distance transmission because of its low line cost, low loss and easy control. But under the action of high-voltage DC electric field, the accumulation of space charge will occur in the DC insulation structure, which will cause the electric field distribution to be distorted, greatly influence the aging and breakdown property of the insulation. At the present stage, due to the limitation of space charge measurement methods, we can only abtain the space charge distribution of panel samples and coaxial samples, but the distribution of space charge in the typical insulation structure cannot be directly measured. Therefore, it is necessary to simulate the distribution of space charge in the typical insulation structure using simulation software based on the existing space charge transport theory.
Because of the complexity, the simulations of space chargre in the past was mainly focused on the calculation of one-dimensional structures. In this paper, the bipolar charge transport model is used to simulate the distribution of space charge and electric field in various insulation structures under the action of high voltage DC electric field, which is based on finite element method by COMSOL Multiphysics software. The simulation process can be mainly divided into two parts: one is the migration of space charge under electric field , the other one is the calculation of the electric field which is affected by space charge density. The space charge part mainly considers the Schottky injection of space charge, the space charge transport in the insulation material under the action of the DC electric field and the coefficient-based space charge extraction. And the electric field distribution part uses the Poisson equation affected by the charge density. These two parts are mutually influential.
Using the above method, this paper uses COMSOL Multiphysics software to perform a series of simulation calculations on one-dimensional structure, two-dimensional structure, two-dimensional axisymmetric structure and typical three-dimensional structure. According to the differences of the models, different boundary conditions are set. After the calculation, a serises of results of spcae charge distribution and the electric field distribution are obtained.
From the simulation results of this paper, it can be seen that not only in the one-dimensional structures, but also in the two-dimensional structures, the two-dimensional axisymmetric structures and the typical three-dimensional structures, the electrons are injected from the negative electrode and extracted from the positive electrode, at the same time, the holes are injected from the positive electrode and extracted from the negative electrode, and in the middle of the structure, the space charge is affected by the electric field and move towards the two poles.
Comparing the one-dimensional simulation results with the experimental results of the panel specimens measured by the PEA method, it can be found that the images of the simulation results are similar to the images of the experimental results. Compared with the experimental data, the simulation results have some differences in the specific values of space charge density and electric field intensity. These differences should be generated by various parameters used in the simulation, but the overall law is consistent. It can be said that the simulation method can well realize the joint simulation of space charge and electric field intensity, and can be applied to calculate the distribution of space charge and electric field intensity in a complex structure.