Polymer and insulation systems degradation leads to an increase of the concentration of charge carriers trapped in deep and shallow traps, i.e. of the volume charge density. Consequently, the amplitudes and the shapes of absorption/resorption currents are altered after normal or incidental ageing. In this work are analyzed the nature and the shape of the absorption/resorption currents, as well as the contribution of its different components, with a focus on those corresponding to space charge. Experimental results obtained on samples before ageing and after accelerated thermal and electrical ageing are presented. It is observed that, after water tree ageing, the volume space charge density increases, also leading to a modification of the absorption/resorption currents. Eventually, the possibility of assessing the ageing state of the samples using the absorption/resorption currents is analyzed.

Keywords: Insulation systems, Ageing, Absorption/Resorption currents, Space charge.