On 24 July 2018, maintenance work was being carried out on behalf of Swissgrid at the Magadino substation (220-kV line, Magadino – Soazza). In the course of the work, an earth fault at 10.43 a.m. led to a temporary interruption of the power supply in some areas of the Sottoceneri.
Just a few minutes later the employees responsible for the installation had already started work to restore the power supply. Also thanks to excellent coordination between the grid control rooms of AET and Swissgrid, the power supply was restored throughout the Sottoceneri region at 11.23 a.m..
Regulations complied with
Following the interruption to the power supply in parts of southern Ticino, Swissgrid conducted an in-depth investigation of the incidents, together with its partners.
Swissgrid carried out internal analyses and also commissioned a report from the
«Technical Commission for High-Voltage Questions» (Fachkommission für Hochspannungsfragen, FKH) . Both the analyses and the external report showed that the preparation work had been carried out correctly. The work assignments, work supervisor’s instructions and the safety measures applied all complied with the regulations.
Even when all the necessary precautions are taken, it is not possible to totally exclude such an incident, even though they rarely arise.
Swissgrid would like to apologise for the inconvenience caused by this service interruption.