Relaxation studies on oil, pressboard and oil-impregnated pressboard

In this relaxation study, the relationship of relaxation characteristics of pure oil, pure pressboard and composite insulation of oil-impregnated pressboard is studied with reference to equilibrium and geometry. Low frequency response of dielectrics is very sensitive to moisture movement and temperature of operation due to variation of relaxation characteristics. In this the roles of components of composite insulation on the integrated insulation system and the geometry have to be explored with application point of view where the geometry of operating oil-filled transformer and the layout of the components vary from one design to another. A simple laboratory study with two components suggests that a simple model can be come up to predict the behavior of composite insulation. Also, it is found that all the insulation characteristics vary with equilibrium time in a narrow band even when the samples were kept in sealed chamber. The model is found to be valid irrespective of geometrical size