Fluted Sheaths for Oil-Filled Pressure Cables

Pressure-difference relations are given for the insulation of oil-filled pressure cables with fluted sheaths. Pressure differences are calculated for a 380-kv cable with such a sheath, and results are compared with those in a cable having a smooth sheath. Pressure drops are four times smaller in cables with fluted sheaths than in those having smooth sheaths when the insulation is uniform and by an order of magnitude smaller and when it is sharply graded, having high-density paper at the conductor.