Swissgrid's construction of the new Rüthi substation and the new line connections improve the security of supply in eastern Switzerland as well as the connection to Austria, while the dismantling of the old line relieves the burden on the Rüthi industrial zone.
The new Rüthi substation as well as the line connections commenced full operation in October 2017 following a construction period of around three years. The SBB also constructed a new substation at the same location.
The new 220 kilovolt outdoor switching substation commenced operation in October 2017 following a construction period of around three years. The switching substation covers an area of around 20,000 m2 and contains six line bays with one coupling bay and was erected in a double busbar design. Five decentralised equipment cabins hold all the field control units. The electronics installed there are connected via control cables to the primary equipment, as well as via power cables and fibre-optic cables to the service building. This industrial building integrates all the functional units for controlling the entire switching substation, as well as the electrical units for the supply of energy as well as to connect to the higher-level grid control room.
An intersection point of several lines of the Swiss transmission grid was created near Rehag. Maintenance or repair work on this crossing pylon normally requires all the connected lines to be shut down. This congestion point was eliminated with the construction of the substation in Rüthi, as the lines can be selectively switched off in the planned switching substation. Consequently security of supply is guaranteed even in the event of maintenance or repair work. The commissioning of the substation in Rüthi enhances energy exchange at transmission grid level. The existing connection between Switzerland and Austria assumes additional significance.
The increase in voltage of the Rüthi – Bonaduz line to 380 kilovolts was included in the Strategic Grid 2015, which the Federal Council published in 2009. In 2015, Swissgrid communicated its grid planning from a national perspective with the «Strategic Grid 2025» and re-evaluated the grid projects. A 380-kilovolt Rüthi – Bonaduz connection is no longer contained in the «Strategic Grid 2025», as it is not necessary to ensure the security of supply until 2025. The 220-kilovolt connections are adequate for transporting the energy from the existing power plants. The «Strategic Grid 2025» grid planning does not provide for a transformation of the Rüthi substation. The switching substation could be expanded with 380-kilovolt substation feeders in a subsequent construction phase. The line connections to the Rüthi substation will be constructed for 380 kilovolts, but will only be operated at 220 kilovolts.
The previous grid structure with the lines of two connections crossing at a single crossing pylon in the Rehag region was not optimal. To separate the grid structure, the east-west and north south connections were fed into the Rüthi substation via appropriate line connections. This enabled the existing line, which led from the Rehag pylon over the Rüthi industrial zone, to be dismantled, which relieves the burden on the Rüthi industrial zone and the hamlet of Rehag.
The western hook-up to the Rüthi substation is a shared Swissgrid / SBB 220 / 132-kilovolt line. The connection leads to the Winkeln substation. The line is designed and insulated for 380 kilovolts, but will continue to be operated at 220 kilovolts.
The eastern line connection to Swissgrid's Rüthi substation will be erected as a 380/220-kilovolt overhead line from the Meiningen substation in Austria. From the border, the existing conductors are to be switched out along a section of roughly 0.6 kilometres and adapted to the conductor cables incoming from Meiningen in terms of cross-section and materials. The line is designed and insulated for 380 kilovolts, but will continue to be operated at 220 kilovolts.
The southern line connection is a 220-kilovolt line to the Bonaduz substation. A total of four new pylons were built over approx. 1.3 kilometres. The line is designed and insulated for 380 kilovolts, but will continue to be operated at 220 kilovolts.
The original plans submitted for the construction of the new substation provided for an adjustment of the northern connection (Montlingen, Mörschwil substation to the Rüthi substation). Due to objections, in 2017 Swissgrid withdrew the request for the planning approval procedure (PAP) for this line connection. Swissgrid is reassessing the possible routes for the northern connection. Both underground as well as overhead line options are being reviewed. Swissgrid will provide information on the progress of the project in due course.
The environmental compatibility report is from 2008. The authors come to the conclusion that any significant risk to the environment can be excluded. The southern line connection will ease the burden on Rüthi's industrial zone and the village of Rehag. According to the report the effects on the environment are limited and no significant additional burden can be detected – even on the BLN (protected landscape) area. It states that the project is legally compliant.
The line crosses a countryside conservation area in the region of Blattenberg. One section lies in the «Säntisgebiet» protected landscape area. As a result of landscape-protection considerations, the pylons will be kept low in the hilly region, which will require the partial height restriction of the forest. An attempt has also been made to select the locations of the pylons in such a way that they slot into the landscape as inconspicuously as possible. The pylons will be coloured in such a way that they match the predominant background colour.
The tension string sets of the substation for the western, northern and eastern line connections are 17.5 metres high, while those for the connection from the south are 30 metres high because these are already designed for the future upgrade to 380 kV. The substation will be adapted to its surroundings by means of suitable colours for the tension string sets and the busbars, as well as for the service building. In addition, there will be natural landscaping with hedges and lines of trees to achieve good integration into the surrounding scenery.
Within the study perimeter according to the Non-Ionising Radiation Ordinance (NISV), there are 2 buildings with locations with sensitive use (OMENs), in which the system limit value of 1 microtesla must be complied with. As the line crosses the valley at a height of around 100 metres at that point, compliance with all the NISV regulations is fully achieved. There is also full compliance with the NISV where the substation is concerned.
The line connections will for the most part affect areas of forestry and agriculture, and not built-up or residential zones. Calculations relating to corona noise show that this will be significantly below the prescribed planning value of 50 dB(A). The regulations from the Noise-Protection Ordinance (LSV) will be fully complied with.
As there is no provision for a transformer in the first phase, the planned 220 kV switching substation will in principle create no noise when in operation. The only exceptions to this will be occasionally audible switching procedures. The nearest building with noise-sensitive rooms is over 250 metres away from the substation. Consequently there will also be full compliance with the LSV with regard to the substation.
Noise emissions during the construction phase will be intermittent and limited to a relatively short duration – including for the scheduled use of a helicopter for construction and installation work. Low-noise procedures will be employed during the construction work and the quiet periods will be adhered to.
Low-emission tools and machinery will be used to reduce air pollution.
There will be a total of 4 pylons in forest areas. Both temporary and permanent clearings will be necessary for the foundation structures, for material and assembly storage facilities and for any future maintenance work. The definitive area to be cleared is 1085 sq m. Temporary clearings amounting to 1573 sq m will be necessary for the storage of materials and for turning vehicles.
The temporary clearings will be made good in situ after removal of the installation sites and access roads. The definitive clearings (1085 sq m) will be replaced in the locality of Montlingen.
This relates particularly to the as yet unapproved northern connection. So there may still be changes in this case if an underground cable has to be built or if an alternative overhead line route has to be found.
The risk to birds of electrocution is low with 380 and 220 kV overhead lines. On the other hand the risk of collision is relatively high, especially for the owls and hobbies to be found in this region. Local protection measures will be checked should any problems arise. It is very unlikely that there will be any striking deterioration of the birds' habitats in the already polluted area.
As a result of the wildlife to be found in the forest on the Blattenberg, construction work in this region should not extend into the winter months to minimise disruption during the construction period. To ensure that the wildlife corridor from Meiningen across the Rhine into the region of the Blattenberg is not restricted in its function, a 30-metre corridor will be left clear between the substation fence and the forest. and upgraded with structures.
No effects are to be expected on any amphibians, reptiles or fish.
The project does not impinge on any moors or bogs, rough pasture or other protected areas of national importance. Other habitats worthy of protection are to be retained and restored. In the event of any lasting adverse effects, compensatory measures will be carried out.
When excavating the Swissgrid and SBB substations, large quantities of valuable soil will be accumulated. This unpolluted material is not to be disposed of at a waste tip, taking up valuable landfill capacity, but is to be reused in the municipality of Rüthi. In this context priority will be given to the restoration of subsidence caused by construction in the «Werben» and «Stöcken» districts, as well as the replacement of heavily polluted material associated with the clean-up of the former landfill site at «Sand». With these soil improvements, the soil quality can be improved in these districts and agricultural usage can be simplified. The removal of soil on the construction site and the intended soil improvement work will only be carried out in good ground and weather conditions and under the supervision of a soil scientist, guaranteeing that they are carried out in an appropriate manner.
No pylons will be erected in the immediate vicinity of surface water, whereas 6 pylons and the entire substation will be in the water pollution control area. The maximum depth of the foundations for the substation, including service building, tension string sets and busbars, will be 2.5 metres. For that reason great care should be taken during the construction work to ensure that the groundwater is not polluted. The water pollution control measures in the area of the substation will be defined together with the environmental construction supervisors.
