Bassecourt – Mühleberg 2020 Grid project

A giant comes to Mühleberg

Author: Stephanie Bos

In the early hours of the morning, the outlines of the historic buildings of the Mühleberg hydroelectric power plant become visible. The first rays of sunshine break through the twilight to reveal the hundred-year-old power plant as well as the Swissgrid substation located right next to it. Orange warning lights appear in the distance, accompanied by engine noises that become louder and louder. On Wehrstrasse, which weaves down to the substation, a heavy transport rolls along at walking pace. The load is pulled by a lorry and pushed by two other vehicles. The load is a real heavyweight: a transformer pole weighing around 170 tons, about 11 metres long, almost 3.6 metres wide and 4.5 metres high. It is being delivered to the substation in Mühleberg. A giant made of steel with 26 axles is crawling its way to Mühleberg: the entire load weighs 362 tons and is almost 75 metres long.

The transformer pole already has a long journey behind it. It travelled along the Rhine by ship from the ABB Power Grids Germany AG plant in Halle an der Saale, Germany, to the Auhafen port in Basel. Next, the journey continued by road in two night stages from Basel via Solothurn and Bern to Mühleberg. One of the experienced drivers skilfully manoeuvres his vehicle along the winding road. «The road leading down to the substation is one of the most demanding stages of this transport. The last bend is relatively tight, but we have planned the trip down to the last detail,» says the driver from the special transport company Friderici SA commenting on the last kilometres before reaching the final destination.

1/3: On the road from Basel to Mühleberg, the heavy transport has to overcome various obstacles.
2/3: The nighttime heavy transport is almost 75 m long.
3/3: During the transport, the 170-ton transformer pole is towed by a lorry and pushed by two other vehicles.
A giant comes to Mühleberg (video in German)

From the power plant, the electricity flows over several grid levels. A transformer is needed between the respective grid levels.
  • Grid levels

    Transformers are electrical machines that connect power grids with different voltages. They convert electrical energy from Swissgrid’s extra-high-voltage grid through several grid levels to the socket. The new transformer, which is being installed here in Mühleberg, is part of the Strategic Grid 2025 and consists of three poles and one reserve pole, which are being transported separately. It will ensure that the electricity can be converted between the voltage levels 380 kilovolts and 220 kilovolts and transported further.

    Mehr erfahren

The increase in voltage between Bassecourt and Mühleberg has been delayed

Mühleberg nuclear power plant was shut down in December 2019. As a result, there is a deficit in Swiss energy production in Swiss Central Plateau amounting to almost 3,000 gigawatt hours of electricity per year. This corresponds to 5% of Switzerland’s energy production and is equivalent to the annual consumption of around 700,000 households. In the medium-term, this missing feed-in will have to be compensated for by higher production from Swiss power plants or by importing electricity from abroad. As the last mild winter and the past months have shown, the greater Berne area will continue to be supplied with sufficient electricity even after the decommissioning of the Mühleberg nuclear power plant. In order to guarantee the long-term supply, the existing transformer capacities in the transmission grid in the Bern / Jura region are now being expanded. Otherwise, it would only be possible to use the electricity imports via the 380-kV grid to a limited extent. This applies not only to Mühleberg but also to other locations such as Laufenburg, Beznau and Romanel, where Swissgrid has already installed and commissioned new transformers. They are important elements in Swissgrid’s «Strategic Grid 2025».

The ground-breaking ceremony for the new transformer in Mühleberg took place on 15 January 2018. However, the transformation from 380 to 220 kilovolts will only improve the security of supply if lines of these two voltage levels meet in the substation and a transformer is in operation. Without increasing the voltage of the line between Bassecourt and Mühleberg from 220 to 380 kilovolts, no transformation can take place in Mühleberg. But the implementation is behind schedule. The Swiss Federal Office of Energy (SFOE) issued the planning approval to increase the voltage of the Bassecourt – Mühleberg line and rejected the objections on 22 August 2019. However, some municipalities and directly affected parties opposed this decision by means of an appeal to the Federal Administrative Court. The Federal Administrative Court confirmed the planning approval for increasing the voltage of the Bassecourt – Mühleberg line, rejecting all complaints, on 15 September 2020. This decision can be appealed against by filing an objection with the Federal Supreme Court (BGer). This is expected to delay the voltage increase of the line by two years.

Nevertheless, the transformer is already being installed and put into operation. This is because the procurement and installation involve lengthy processes. The public tender and production at the manufacturer’s premises are very time-consuming. Once the 380-kV line between Bassecourt and Mühleberg – which has already been technically designed for 380 kV – is commissioned, the transformer will be ready for operation.

Unloading with combined forces

The heavy transport has meanwhile arrived at the substation. The sun has now risen, affording the drivers and their helpers sufficient light to work. The transformer pole is unloaded with many helping hands and eyes. Because unloading is a precision job, just like transport. The transformer pole is lifted and placed on the rail with the help of hydraulic hoists. From here it is drawn by a pulley system into the transformer chamber, where it can soon be assembled and put into operation together with the other three transformer poles. This is scheduled to take place by November, so that the new transformer in Mühleberg will be ready for operation by the end of 2020, thus completing another stage in the «Strategic Grid 2025» project. The drivers and helpers begin their return journey, exhausted from the strenuous night’s work. «Thanks to the good cooperation, the transport was completed without a hitch. We are an experienced team, so everyone knows what to do,» says one of the drivers as he climbs into the cab of his lorry and starts the engine.

1/2: The transformer pole is lifted and placed on the rails.
2/2: The transformer pole is drawn into the chamber with the help of a pulley system.


Stephanie Bos
Stephanie Bos

Communication Manager

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