Impregnation model and experimental investigation of vegetable insulating oil-paper insulation

Adaptation of the impregnation conditions of cellulosic transformer solids to the use of natural esters

“…3. A linear relationship between both variables can be verified (4). The slopes of these graphs are known as the impregnation ratio (cm/√min), which is representative of the impregnation speed of the samples [3].…”

“…Based on this, it can be asserted that viscosity variation predominates over surface tension when deciding impregnation temperatures. Previously, other authors [4] have already stated that the capillary effect, formed by the surface tension and the contact angle between the liquid and the dielectric insulator, hardly suffer any variation between the different combinations of materials. On the other hand, it is seen that vegetable oil undergoes a greater increase in the impregnation ratio, as a result of the reduction of viscosity in natural esters is greater than that suffered by mineral oil (Fig.…”

“…Under conditions where during impregnation there is no difference between the external and internal capillary pressure, the pressure in the liquid is due to the pressure caused by surface tension. Combining equation ( 2) and ( 3), the impregnation length can be expressed as shown in (4).…”

A Brief Review of the Impregnation Process with Dielectric Fluids of Cellulosic Materials Used in Electric Power Transformers

“…The simplification of the physics of this impregnation process means that it can b considered to be carried out by capillarity through the pores of the material, and therefor it is carried out according to the Hagen-Poiseuille Law [14,[17][18][19]; this implies that it i subject to both the adhesion forces between the solid and the liquid, as well as the cohesion forces of the fluid. Before beginning to develop the theory of impregnation, it should be noted that in [16], the author, in addition to discussing the reasons why cellulosic dielectrics in electrical equipment are impregnated, presented different techniques of impregnation used in the manufacture of electrical machines, analyzing their advantages and disadvantages.…”

“…The simplification of the physics of this impregnation process means that it can be considered to be carried out by capillarity through the pores of the material, and therefore it is carried out according to the Hagen-Poiseuille Law [14,[17][18][19]; this implies that it is subject to both the adhesion forces between the solid and the liquid, as well as the cohesion forces of the fluid.…”