Mechanical Effects Load Cycling on Pipe-Type Cable

There is growing evidence that some service outages, in or immediately adjacent to the splice sleeves of heavily loaded EHV pipe-type cable lines, were associated with thermo-mechanical bending. This evidence, plus an additional instance of trouble induced by a mechanical mechanism in the EPRI-Manufacturers 550-kV Waltz Mill test program1, prompted a follow-up study. This paper reports on a project designed to assess the effect of cyclical cable movement on the paper-oil dielectric of Cable A, with conductor temperatures reaching as high as 130°C. A detailed examination of the cable after the loading schedule had been completed, revealed no evidence of significant displacement or damage to the paper tapes which would affect the service life of the cable. This work has been funded by the Electric Power Research Institute as a portion of their comprehensive program on underground transmission.