A New procedure to compare the social costs of EHV-HV overhead lines and underground XLPE cables

In recent years the evolution and enhanced performance of underground cables with extruded insulations such as XLPE has re-focused attention towards the installation of underground HV and EHV transmission lines. The liberalisation of the energy market and the need to connect new power plants to the grid has further stimulated the growing requirements to install a significant quantity of underground cables. In the near future, in order to sustain the transmission grid development, a comparative economic analysis of innovative and traditional transmission lines will be essential. The planning choices will have to be consistent with safety, reliability and operation constraints, taking into account both the transmission and congestion costs and the value of undelivered energy in the economic scenario as well as ensuring the fundamental technical infrastructure of the transmission grid to ensure the efficient matching of demand and supply of electrical energy. The choice between the two solutions overhead lines (OHL) and underground cable (UGC) is merely driven by technical, environmental, and economic considerations. Some of the authors have developed [1, 2] a general comparative evaluation between all the transmission options (OHL, AC cable, HVDC and GIL). In this paper, the analysis has been focused on and restricted to ac underground cables and overhead lines. The paper compares costs of overhead lines and underground XLPE cables, both being possible options for the construction of new lines in existing grids. All operating costs over the life of the asset can be converted into an equivalent capital sum at the start of the project life and so these costs can be added to the capital cost of the investment. In addition to the economic costs, this paper also quantifies the environmental costs of a transmission facility, in terms of the burden on the built/developed/occupied land or territory. The presence of an electro-magnetic field exceeding the value set by national Laws (or Rules or Standards) may create a quarantined area of land unavailable for human activities or development. The economic impact [€/m2] to the land crossed by a transmission line can be estimated taking into account the loss of value of the rights-of-way. The methodology can be applied, modifying its constituent parameters, to many different configurations and countries.