Development of Special Insulating Paper for EHV Power Cable

A special insulating paper, developed for use in EHV power cable, is described. Generally speaking, where the insulating paper is made of the same pulp, the thinner the paper, the higher the impulse breakdown strength, and the lower the power factor. In view of this fact, a special insulating paper (combination paper), with a high-impulse breakdown strength, low power factor, and great mechanical strength has been developed by making thin insulating paper and cementing a plurality of sheets together with a suitable adhesive. 275-kV, 1 ×1200 mm2 oil-filled cable and 275-kV, 3 ×1400 mm2 pipe-type oil-filled cable using this combination insulating paper have been proved to possess excellent properties, such as shown in Table IV and Fig. 10, respectively, and the special characteristics of the insulating paper are fully displayed in the finished cable. The motive for the development of the combination paper, its theoretical background, and the properties of the insulating paper and of the cable using that insulating paper are reported.