Technical Considerations for Undergrounding of EHV Lines

摘要

The installation of extra high voltage (EHV) overhead transmission lines face opposition from environmental groups, local jurisdictions and community groups due to impacts such as aesthetics, magnetic field exposure, and occupation of land. Utilities, transmission developers and power generating companies increasingly require conducting environmental impact studies which include alternatives to evaluate undergrounding lines or sections of lines especially as their corridors traverse rural and residential areas, enter congested areas in urban cities to access substations, are adjacent to sensitive receptors such as schools, urban redevelopment areas, or are in close proximity to areas of scenic beauty or historical or cultural sites. Consideration of undergrounding options is also being included in environmental studies as part of the regulatory process to obtain approval for the project. EHV underground cables require careful considerations with respect to overall system selection, design, ampacity, loading, reactive compensation, transition stations, switching, installation requirements, repair, maintenance and cost. This paper provides an analysis of available cable system technologies for EHV applications and addresses other technical requirements for conversion of EHV lines to EHV underground cables.