Completion of repairs at Albula Pass

30.07.2019

In mid-April, TSCNET shareholder Swissgrid, the Swiss transmission system operator (TSO), began repairing the 380kV lines on the Albula Pass in the canton of Grisons, which had been damaged by the windstorm Adrian (Vaia in the German-speaking area), in the night of 29 to 30 October 2018. Since then, the two affected lines (Filisur-Robbia and Pradella-Robbia-Sils) were out of service, as Swissgrid decided for safety reasons not to erect a temporary connection in winter due to the danger of avalanches. The four damaged pylons and the conductors have now been replaced. On 29 July 2019, the lines were put back in operation as scheduled.

During the outage of the lines, grid security in the transmission system was always guaranteed and there were no supply interruptions. But the importance of the line as a north-south link made the repair particularly urgent. Thanks to partial snow clearance by the Civil Engineering Office of Grisons and a temporary avalanche protection system, Swissgrid was able to start work even before the official opening of the Albulapass road. Thus, Swissgrid was already able to start work on the four pylons on 15 April. The old foundations were removed, and new ones laid. The pylons were then built, and the conductors installed. The new pylons withstand even greater wind forces due to their stronger foundations and supporting structures. Two pylons now also have foundations with integrated avalanche protection.

Strict safety regulations were followed during the work. The high alpine terrain and the unpredictable weather of the snowy winter of 2018/19 presented the repair team with major challenges. The local avalanche commission issued an avalanche bulletin every day and activities were planned based on this information. The specialists on the construction sites were equipped with avalanche detectors and a container would have provided 48 hours of protection in an emergency. The work was accident-free. The Swiss TSO also developed and implemented a comprehensive environmental plan to protect the high alpine landscape. For example, the soil layers were removed and stored separately and returned to their original place after completion of the foundation work. The original state of the surroundings was then restored as far as possible.

Swissgrid has finished repair work on the damaged overhead lines at the Albula Pass (picture: Swissgrid)

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Pylon repair started at Albula Pass

25.05.2019

The windstorm Adrian (Vaia in the German-speaking area) was one of the most devastating storms of the European storm season 2018-19, mainly affecting the northern Mediterranean and Alpine regions. It not only damaged the Venetian Basilica of San Marco and flooded 75% of Venice, but also destroyed transmission lines at the Albula Pass: In the night to 30 October 2018, four pylons from TSCNET shareholder Swissgrid, the Swiss transmission system operator (TSO) bent or collapsed at the high mountain pass in the Canton of Grisons.

Since then, the two affected 380kV lines (Filisur-Robbia and Pradella-Robbia-Sils) have been out of operation, as Swissgrid has decided for safety reasons not to erect a provisional connection with emergency masts in winter due to the danger of avalanches. Nevertheless, grid security in the transmission grid is ensured at all times and there have been no supply interruptions. While security and supply are guaranteed, however, transit capacity to Italy had to be reduced until the line is restored.

Swissgrid began repairing the 380kV lines in mid-April and is now replacing the four broken pylons whose foundations are currently being reconstructed. New pylons and the conductor ropes will then be installed. If everything goes according to plan, the two lines will go operational again at the end of July.

Swissgrid has commenced repair work on the damaged overhead lines at the Albula Pass (picture: Swissgrid)

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Repairs at the Albulapass as of May 2019

16.11.2018

In the night to Tuesday, 30 October 2018, the hurricane Vaia damaged the power transmission lines of the TSCNET shareholder Swissgrid, the Swiss transmission system operator (TSO), at the Albula Pass in the canton of Grisons. Four overhead line masts bent or collapsed there. The two affected 380 kV lines Filisur – Robbia and Pradella – Robbia – Sils have since been out of service. The connection from Pradella to Robbia of the 380 kV line Pradella – Robbia – Sils was put back into operation on 31 October. In the meantime, the clearing work on site has been completed with the dismantling of the conductor ropes and the damaged masts with the help of a heavy-duty helicopter. The repair work has now been scheduled for late spring 2019: Repair work on the two defective 380kV lines will start in May next year.

Overall, the repair work on the high-alpine site is estimated to take two to three months. The lines are scheduled to be put back into operation at the end of July 2019. The failure of the two lines will not affect the security of supply in Switzerland or in the affected regions. However, transit capacity to Italy is somewhat limited: The monthly net transfer capacity (NTC) has been reduced by a total of 900MW.

Swissgrid has decided against a provisional solution with emergency masts for various reasons. In particular, safety concerns speak against a temporary solution. The erection of emergency masts in wintery high mountains involves many risks for man and material. In addition, the time window for a repair up to the first large snowfall would presumably be very narrow. After that, the risk of repair and operation increases considerably due to the weather conditions, for example snow and ice load or the increasing danger of avalanches as well as structural engineering conditions. The measures are being taken in close consultation with the Italian grid operator TERNA and other neighbouring TSOs.

Swissgrid announced to repair the damaged transmission lines at the Albula Pass in late spring 2019 (picture by Adrian Michael, Creative Commons, Wikimedia)

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