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The new 380/220 kV transformer supports import capacity at Switzerland’s northern borders and improves security of supply in the Zurich area.
After overcoming the strained energy and grid situation in the winter of 2015/2016, and in close cooperation with Axpo Power AG, Swissgrid has accelerated the expansion of the Beznau substation, planned as part of the «Strategic Grid 2025», with a new 380/220 kV transformer.
Transformer in use following successful test operation
The transformer was integrated into the existing outdoor substations (380 kV and 220 kV) on the island in the middle of the Aare in Beznau, a site operated by Axpo. A test operation lasting several days was carried out in mid-March 2017 to assess the functions of the protection and control systems in grid operations. The transformer successfully passed the battery of tests, and is now in operation until power plant unit 1 of the Beznau nuclear power plant is reconnected to the grid.
The new 380/220 kV transformer in the Beznau substation is not in continuous operation. It is intended as a backup for use as an emergency transformer. Swissgrid can activate the transformer in critical grid situations at short notice or in the event of the imminent threat of an energy shortage following agreement with the Beznau nuclear power plant. Otherwise, the transformer can be put into operation when at least one of the nuclear power plant’s units is not on the grid.
In these situations, the transformer serves to relieve the pressure on existing transformers in the transmission system, supports import capacity at Switzerland’s northern borders and improves security of supply in the Zurich area.
In July 2016, the Federal Inspectorate for Heavy Current Installations (ESTI) issued the planning approval decision for the creation of a new 380/220 kV transformer in the Beznau switching substation. Swissgrid immediately began construction work in the substation. This was completed in March 2017. The transformer was transported to the Beznau substation in three pieces using an oversize vehicle at the end of November 2016 and the start of January 2017.
Key figures
Power: 800 MVA
Size: per transformer/pole 11 m x 8 m
Weight: per transformer/pole 333 tonnes