Space Charge Characterization of XLPE peelings with a Cable prehistory: Before and After AC Endurance Tests

In the E.U. research programme ARTEMIS 90 kV cables insulated using the same batch of XLPE were stressed under different electro-thermal conditions for various durations. Thin peelings of the insulation of the cable sections stressed in this way are compared with peelings taken from an unstressed cable section, through their ac electro-thermal endurance measured under the same test conditions, to see whether or not the cable stressing had altered the inherent endurance capability of the insulation material i.e. aged it, and to identify markers for the dominating process/es that degraded the materials. Their space charge behaviour was also measured by the Pulse-Electro-Acoustic (PEA) technique before and after the endurance test, in order to characterise the material from the stressed cables and to identify changes brought about during the endurance test. The measurements focussed on the accumulation of space charge under a standard measuring condition of 50kV/mm at room temperature, and its subsequent decay. The results show that the ARTEMIS stressing as well as the endurance test introduced changes to the space charge behaviour.