ASSESSMENT OF THE STATE OF INSULATION SYSTEMS FOR LARGE ELECTRICAL MACHINES

Abstract- Degradation of insulation systems of electrical equipments increases the space charge density and the concentration of electrical dipoles. By consequence, the permittivity, the resistivity and the maximal values and slopes of the absorption/resorption currents change with the ageing of insulation systems. In this paper an analysis of the nature and shapes of the absorption/resorption currents and the importance of their components is presented. The experimental study concerns the current measurements of the accelerated aged samples. The obtained results show that the thermal stresses influence the dielectric properties and the values and the shapes of the absorption/resorption currents. The possibility of assessment of the state of insulation systems from currents measurements is discussed