Low impact high voltage underground cable systems

Year

2017

Organisation

Greenconnector

Description

Worldenergy is developing an underground HVDC cross-border interconnector between Italy and Switzerland (Greenconnector), while utilising existing infrastructure for the cable’s installation.  

 

Highlights:

  • Reusing 80km of existing infrastructure (old pipeline) and optimising cable design and installation methods
  • Cable laying on the bottom of a closed, 300m deep lake, using conventional marine techniques, even in the absence of cable laying ships  

 

Scope:

The practice can serve as a reference case for long distance installations inside pipelines and for cable laying on the bottom of closed lakes.  

 

Main information:

Renewable energy North and South of the Alps is weakly correlated; thus, the region would benefit greatly from removing any congestion bottlenecks and allowing bi-directional exchange of renewable electricity. The increase of the overall import-export capacity between Switzerland and Italy via the Greenconnector project will positively impact market integration, competition and system flexibility. As such large-scale grid infrastructure projects can often cause significant environmental impacts, project developers aim to develop approaches that try to minimise such impacts and eventually lead to higher public acceptance. This is especially true of the Alpine region, where new corridors are difficult to find and are environmentally sensitive because of the narrow valleys and attractive landscapes.  

Greenconnector’s environmentally friendly approach consists of the use of an out of service oil pipeline for the cable’s installation, and cable laying on the bottom of a lake. These methods are expected to result in numerous technical, economic, environmental and visual impact benefits: from better cable protection and higher reliability, to significant reductions of installation cost and time, and from minimising ground and natural habitat disruption, to no cable visibility along the entire route and a reduced route length. 

 

Additional information:

  • Worldenergy is developing the Greenconnector project in cooperation with suppliers and civil works contractors, and local authorities. The HVDC cross-border interconnector project (1000MW, 400kV DC) is located between Lombardy (Italy) and Graubünden (Switzerland). The route length is 150km of underground DC cable, of which 47km are laid on the bottom of lake Como in Italy and 80km inside the existing pipeline.  
  • The project started in 2003, with the next 15 years being dedicated to data collection, design, planning and permitting also via conducting a number of technical and environmental studies and surveys. It has been permitted in Italy, with unanimous approval by all local and central administrations involved along the 120km route on the Italian side. Construction will begin in 2019, with an expected commissioning date in 2022.