CABLE SYSTEMS IN MULTI PURPOSE OR SHARED STRUCTURES

With the increase in demand and challenges of installing high voltage (HV) and extra high voltage (EHV) cables in dense urban and other locations, structures such as tunnels and bridges for multipurpose use are becoming an attractive option. They offer a potential for reduced overall costs, environmental advantages and less disruption to the community in the installation, maintenance and replacement of cables and other services. However, the relative costs for the construction, operation or sharing structures have not been considered in any detail in this brochure. The structure of the brochure is such that the reader can study Sections 1 to 5 and review the examples described in Section 8 to decide if a shared structure is appropriate. If it is decided to use a shared structure then Sections 6 and 7 that deal with the different technical and administrative issues, should be a useful guide in the design and implementation of such a system. Section 8 is a review of the international experience of HV cables in multipurpose or shared structures. Future trends are summarised in Section 9. A large appendix resumes the results of TF B1-14 which has yielded an extremely useful and comprehensive questionnaire on the synergic use of cables and structures. The same issue developed for Gas Insulated Lines has been investigated by JWG B3/B1.09 in the TB 351 "Application of Long High Capacity Gas Insulated Lines in Structures". Due to the complexity of cabling in general, the group elected to mainly deal with cable systems of 50 kV and above in multipurpose and shared structures where it felt that the investments are most likely to be made. However, there is no limitation to applying the principles to cables of lower voltages.