Lines versus Cables: Consider All Factors

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 EHV and HV transmission circuits. The liberalisation of the energy market and the need to connect new power plants to the grid has stimulated growing requirements to extend existing transmission systems. The planning choice between overhead line and underground cable will have to be consistent with safety, reliability and operational constraints to ensure the capacity of the transmission grid efficiently matches the demand and supply of electrical energy. The choice between the two alternatives overhead lines (OHL) and underground cable (UGC) is driven by technical, environmental, and economic considerations. The operating costs over the life of the asset can be converted into an equivalent capital sum at the start of the project life and added to the capital cost of the investment. The environmental costs of a transmission facility can be quantified 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