Mitigating construction risk in the design and planning of high-voltage transmission lines

Abstract

The Eskom transmission network in South Africa is rapidly expanding with the addition of new power stations such as Medupi, Kusile and multiple independent power producers. The changing grid code requirements to ensure stabilising of the grid in certain areas, and the simple need for expansion to new areas also require expanding the transmission network. The constructions of these lines come with various risks to personnel, the quality of the end product and the environment that need to be managed from a project management, design engineering and construction point of view. The lines use a combination of structures, some of which are very old and were designed before new high capacity cranes and other similar construction equipment were available. This study investigates the methods used to construct transmission lines and how the design of new methods with new technology can positively impact the end product. It focuses on the erection of galvanised lattice steel structures, although other processes such as foundations and stringing are mentioned. The new method of erection of the cross-rope structure type with two cranes was tested on a construction site. The method of erection with the use of a spreader bar was tested at the Eskom structure test centre in Rosherville. Both tests were completed successfully. The method of erecting the self-supporting suspension structure in fewer lifts was tested on site but needs modifications to the structure to mitigate some construction risks. The erection of the guyed-V structure type with the hardware and insulators was tested on a construction site and was also completed successfully.