Three experimental midvoltage XLPE cables, C2, C3 and C4, rated respectively as 'good', 'very good' and 'bad' in perforation tests, are studied. All these cables have been systematically measured by PEA as produced and after being annealed at 90ºC and 120ºC up to 672 hours. Measured internal charge of cable C4 at least doubles that of cables C2 and C3. Evolution with annealing show as well differences in the reticulation process carried out during cable C2 and C3 preparation, which can explain why cable C3 performs better than C2 in perforation tests. Infrared spectroscopy measurements (IR) showed differences in components injected from the external semiconducting layer (SC) into the isolation during annealing. These results explain other observed differences in PEA measurements with regard of the SC type of each cable. To sum up, combination of PEA and IR measurements are a useful tool in understanding charge relaxation processes and XLPE cable performance.

Peer Reviewed