The Study Of Breakdown In Dielectrics Based On Fractal Technology

The fractal geometry is a powerful tool to study the irregular figures in nature andproject. On the study of discharge structures in dielectric, the breakdown phenomenonis very complicated and often occurs by means of narrow discharge channels thatexhibit a strong tendency to branching into complicated stochastic patterns. Amongthese breakdown figures, many of them present a close structural similarity andstochastic characteristics, so they can be studied with fractal technology.The study in this field always uses fractal technology to simulate the developmentof breakdown in dielectrics. This paper bases on the basic two-dimensional breakdownfractal models NPW and WZ model, and use MATLAB7.0 to program and carry out thesimulation for the development of discharge structures. We should both consider thedeterministic and stochastic factors during the development of discharge. Comparingthe simulation results, the effects of model parameters on the development of theelectrical trees are discussed.Based on the WZ model, we simulate the development of electrical trees when anew dielectric layer whose breakdown strength is much more than that of the formerdielectric is embedded in the former dielectric, and that equals to extend the meanbreakdown distance, so it improves the insulation performance. In addition, we alsoanalyze the multilayer high gradient insulator in WZ model. When embed several metallayers in dielectric, the electrical field distribution becomes more symmetrical, and thelocal field becomes weaker, so the points which satisfy the growth condition becomeless, and the development of the electrical trees is restrained.Further more, we introduce space charge and partial discharge in the model, anddevelop a new three-dimensional discharge model. Comparing simulation figures, wefind the relationship between the model parameter and the development of electricaltrees. The simulation figures are much similar to electrical trees got from experiments.