A new power transformer joins CERN’s armada

Feb 25, 2019

Early in September, a massive device weighing 224 tonnes and measuring 15 metres in length was loaded onto a barge in Nijmegen, the Netherlands. After navigating the Rhine river all the way to Basel, the whole structure took to the road bound for Geneva in a 66-metre-long convoy. Over the following six days, it moved at 10 km/h on average, mostly travelling at night. The final destination: CERN. On the morning of 4 October at 4.30 a.m., the behemoth arrived.

The spectacular shipment was CERN’s newest and biggest power transformer, for the new BE2 electrical substation that is located strategically between the Laboratory’s Meyrin and Prévessin sites. The substation has been built to provide redundancy to the existing 66-kilovolt (kV) electrical substation located in Prévessin, which is used to supply critical loads, such as those relating to the LHC. The new transformer is so massive that the complex process of unloading it took four full days.

A convoy of trucks carrying a massive power transformer
The whole structure travelled to Geneva mostly at night, in a 66-metre-long convoy, moving at 10 km/h on average. (Image: Pablo Gaviglio/CERN)

Transformers are typically used to increase the voltage along the transmission path (step-up transformers) or to decrease it (step-down transformers), through electromagnetic induction. Electricity is transferred from power plants at high voltages and arrives at CERN at 400 kV. This must ultimately be lowered to 66 kV or 18 kV, the levels at which much of the Laboratory’s electrical equipment operates, by means of step-down transformers.

The newly arrived 400 kV power transformer will be the sixth such device in CERN’s fleet. With a height of 9.7 metres, a length of 15.8 metres and a width of 3.9 metres, the completely assembled transformer will weigh 331.9 tonnes, making it twice as large as any of the existing power transformers at CERN. Baptised “Olive” for the olive-green colour of its tank, it will be filled with 82 000 litres of insulation oil once it is fully installed. It will be energised in early December, and is scheduled to be fully operational at the beginning of 2019. Olive will supply CERN for a significant part of the second Long Shutdown (LS2), when the other five 400 kV transformers are shut down for maintenance.

Olive is designed to respect the strictest environmental standards, and its specially constructed noise-cancellation panels make it extremely quiet for a power transformer of its size. In addition, the new BE2 electrical substation contains an advanced oil-retention and fire-suppression system to protect the environment in the unlikely event of a fire or an oil leak.

“The new BE2 electrical substation relies on industrial products and services from Switzerland, the Netherlands, France, Portugal, Germany, Italy, Spain and Hungary through several contracts placed by CERN. A number of pieces of high-voltage equipment in the existing 400 kV substation in Prévessin will also be replaced during LS2 in the framework of the project”, says Marko Wolf, project manager in the EN-EL group.

This substation is the result of more than four years of work in conjunction with multiple stakeholders, notably RTE France (Réseau de Transport d’Electricité), who built an additional transmission feeder bay in their 400 kV Bois-Tollot substation to connect to the BE2 substation.

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