The impregnation of Solid Insulation with Synthetic Esters
Seeing that the kinematic viscosity, the number of open pores in the insulation material, diameter of the pores, inside and outside pressure of the material will determine the rate of liquid penetration into the insulating material. Impregnation for synthetic esters at 60⁰ C is the same as for mineral oil at 20⁰ C. It should be noted that the impregnation of pressboard with synthetic esters take approximately 1.5 times longer than mineral oil.
The breakdown characteristics of solid insulation components impregnated with synthetic esters
According to experimental data, has a much higher electrical permittivity (3.2) than mineral oil (2.2) This causes the pressboard to be impregnated with this liquid and it also has a greater electrical permittivity, this result in a decreased value of the electrical field and an increase in the electrical strength.
Further experiments revealed however that pressboard impregnated with esters are more susceptible to the influence of partial discharge, which is not an ideal scenario in insulating structures. [2]
Electrical field distribution in synthetic ester insulating systems
A cellulosic paper and synthetic ester system has been studied as well as the cellulosic paper and mineral oil system. It was found that the intensity of the electrical field is higher in the paper with the synthetic ester dielectric liquid, this is the electrical field in the paper. However for the mineral oil system, the electrical field in the paper is lower, but in the oil, it is higher. The fact that the higher electrical permittivity of synthetic esters with that of mineral oils causes a decrease in the electrical field in the liquid, but an increase in the electrical field stress of the solid insulation. The difference between the distinctive regions are lower in the case of ester liquids, this acts to their benefit. [3]