Design for new type of main insulation of 35kV electric power transformer based on electric field analysis

The reason of main insulation structure breakdown based on liquid and solid discharge theory is analyzed. The new design schemes of main insulation structure for 35 kV electric power transformer are presented based on electric field analysis. FEM is introduced to calculate the electric filed of new type of main insulation structure. The electric field distribution, maximum and position of electric field intensity are shown. A way of placing angle ring above high voltage is used to improve the electric field distribution. The electric field distribution for new structure is more uniform than the old main insulation structure.