Conductivity () in XLPE insulation of power cables annealed at 90 ºC attemperatures between 50 and 97 ºC has been measured. In all cases there is an initialincrease in conductivity that develops a maximum and finally decreases for longannealing times. This maximum appears in the sample annealed 20 days whenconductivity is measured at 50 ºC and shifts gradually to higher annealing times up to40 days when the measurement is performed at 97 ºC. A linear behavior of ln() versusT -1/4 is observed, which implies that the transport mechanism is basically via thermallyassisted hopping conduction. Infrared spectroscopy indicates that, during annealing,some chemical species diffuse from the semiconducting shields (SC) into the XLPE.Thermally stimulated depolarization currents technique (TSDC) and intensity-currentmeasurements (I-V) point out as well the presence of this diffusion process thatbecomes less significant after long annealing times. The initial increase in isexplained in terms of the increase in traps density due to the diffusion process from theSC shields. Long term decrease in is justified by the observed decrease of diffusionrate for long annealing times.
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