Lessons Learnt from Permitting and Consent relevant to AC UGC Lines: The 150 kV “Cagliari Sud - Rumianca” case

摘要

In the last four years the increase of AC underground cables within the Italian Grid has been around37%, with a quite constant increase around 11% per year. Future investments in undergroundingprojects are expected to grow up as well in Italy.Cable lines are usually preferred in urban areas, places where tall structures can represent obstacles(e.g. when close to airports), due to environmental constraints and prescriptions, water bodies crossing(e.g. rivers, lagoons, etc.) .On the other hand, public opinion generally has a negative consideration of OHL, even where itrepresents the right solution: rural areas dedicated to crops, forests in which cables can interfere withshallow roots, mountain areas where the lack of practicable routes could force to great constructionworks, areas with high hydrogeological and seismic risks.First of all the document describes the authorization process in its general form, taking into accountthe planning phase, the consultation process, following to describe permitting procedures in the Italiannormative framework, in which, according to National Law 152/06, an Environmental ImpactAssessment for AC underground cables for length ≥ 40 km is required.The aim of the paper is to stress particularly the authorization process related both to technical andenvironmental constraints dealt with the project phase for a cable line in Italy, highlighting that thepermitting procedures and consents have often a very long duration as well as overhead lines, givingrise sometimes to unpredictable delays. In this respect, an experience on the 150 kV “Cagliari Sud -Rumianca” connection is reported, with its main characteristics. The need of a shunt reactance of 36MVAR is also presented.In particular, such project underwent different troubles during both the consultation and theauthorization phases. At the beginning, a solution with OHL was planned, according to the 2005 TernaGrid Development Plan (GDP) [2], to increase reliability of the local grid.After the consultation process with Municipalities and Local Authorities, Terna was pushed to moveto UGC solution, changing its previsions into the GDP 2007 [2]. In this way, cable line was perceivedby public as a good solution to reduce the environmental impacts.Nevertheless, during the authorization process, some troubles raised up by some Municipalities inwhich deemed that the cable route needed to be changed in some parts with a very strong impact onthe project: a section of the route was even asked to be changed from land to the sea and someinvestigations had to be taken into account for contaminated areas and hydrogeological aspects due toan unexpected flood. Such natural event led several months of delay in the authorization phase,although safe measures have been adopted into the project to prevent damages from hydrogeologicalevents.Other critical aspects of this UGC line are described, such as: interference with roads under projectand existing traffic, problems during construction phase with rocks and soil due to presence ofcontaminated industrial areas along the route, which established prescriptions to reclaim soils to theirnatural use.General lessons learnt from this experience are explained, showing comparison in terms of time andcosts between the underground solution and the overhead one, and feedbacks from consultation withlocal authorities and from the overall permitting process.