Measurement of the force induced by thermal expansion of conductor of MV cables and impact on MV joints

Cable links with a high current load become more usual, especially with wind power generation and third party access to mv cable networks. Analyses of failed medium voltage joints from high loaded cable links in The Netherlands tend to indicate that thermo-mechanical forces play an important role in most failure mechanisms. Theoretically, huge forces can be expected on MV joints, due to the expansion of the conductors. In order to compare the theoretical forces with those that can actually occur during the real life of the accessories, the forces exerted by the widely used stranded compacted and solid aluminium conductors of 240 and 630 mm² were measured. This paper presents the results of those measurements and points out that those forces are never considered during the qualification of the accessories according to the relevant standards.