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Long-term and short-term electrical properties of impregnated paper and polymeric insulating materials employed in oil-filled HVDC cables, that is, paper and paper-polypropylene-paper laminates, are investigated in this paper. Specimens were subjected to electric strength tests, life tests and space charge measurements, at different electrical field and temperatures. The results indicate that PPPL is by far superior to paper in terms of time-to-breakdown. As regards, space charge, paper accumulates more charge than PPPL but, generally, it is able to expel it at a slightly faster rate.