Simulation analysis on FDS of power transformer by FEM approach

Abstract

In order to get more effective and accuracy results of condition evaluation for transformer, the FDS characteristics of oil-paper insulating systems are studied by using Finite Element Method (FEM) in this paper. Firstly, the FDS properties of oil-immersed paper (OIP) are measured in lab. Secondly, a model based on 110kV transformer's actual dimensions is proposed by FEM and XY model, respectively. By comparing the results of two methods, the validity and accuracy of the FEM for solving FDS characteristic is verified. Finally, the impact that moisture content in pressboard and the pressboard aging on FDS characteristics of oil-paper insulating systems is investigated by FEM approach. The results indicate that the electric field distortion due to the dielectric materials' discontinuous effect is taken into consideration in FEM simulation. And the FEM model can be used to analyze the FDS of complex structures. The influence of moisture on FDS is mainly reflected in low frequencies. The influence of oil conductivity on FDS moves to higher frequencies with oil conductivity increasing. As the aging proceeds, the dielectric loss factor increases in low frequencies below 0.01Hz due to moisture produced from aging of pressboard. And it also increases in high frequencies of 1Hz to 100Hz determined by dielectric polarization.