Countermeasure for Thermo-Mechanical Bending of Load Cycling on 275 KV Pipe-Type Cable

Generally the cable cores of Pipe-type Oil-Filled cables are left to snake freely due to seasonal temperature change and load cycling. In the case of a large sized cable where the clearance between the cable cores and the internal surface of the pipe is large, the bending moment of the cable at the curve increases while the EI of the cable increases at the same time. The radii of curvature at some points of such cable lines may be forced to become quite severe, and it is forseeable that repeated bendings will lead to dielectric failures in extreme cases. This paper reports on the system of absorbing thermal expansion by installing curved offset pipes in 275 kV 3 x 2,500 mm2 POF cable lines, and also describes the test results together with the concluding evaluation of the system.