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.