Line maintenance under extra high voltage

14.10.2020

For the maintenance of extra-high voltage overhead lines, transmission system operators (TSOs) normally have to shut down the line in question. This practice is more than understandable in view of occupational safety. On the other hand, it also reduces transmission capacity and increases the workload of the staff in the TSO’s network control centre who are in charge of coordinating the shutdown. An ideal solution must thus take both into account: first and foremost, the protection of employees and then the best possible utilisation of the facilities.

The Swiss TSO and TSCNET shareholder Swissgrid has carried out a pilot test on the 380kV line Chamoson-Romanel near Lausanne. At the beginning of October, just a few hundred metres from the Romanel substation and in the landing corridor of Lausanne-Blécherette airport, an orange signal ball was installed on the ground wire of the line, which had not been switched off beforehand. Swissgrid drew on the expertise and technology of Airtelis, a subsidiary of the French TSO RTE. Since the 1980s, Airtelis has been working on methods and technologies that allow maintenance work on extra-high voltage lines to be carried out safely and without switching off the power.

An Airtelis/RTE team of around 15 specialists travelled to the western Swiss canton of Vaud. An RTE helicopter also arrived on site, adapted to the work under voltage and equipped with various mirrors and an on-board camera. A special nacelle was attached to the helicopter with insulating anti-rotation ropes. Two Airtelis team members climbed into the nacelle to install the signal ball during the flight. They wore a suit specially designed for work under voltage, which protects its wearer like a Faraday cage. The installation work was carried out exactly as planned and was safely completed after 30 minutes. Swissgrid will now analyse the experience gained from this pilot project, in which the first maintenance work under voltage was carried out in Switzerland, and assess whether this technology should be used generally in future.

Swissgrid has carried out a test on the maintenance of high-voltage overhead lines without disconnecting them from the grid (picture: Swissgrid)

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Automated intraday capacity allocation at Austrian-Swiss border

05.10.2020

The separation of the bidding zones of Germany (including Luxembourg) and Austria on 1 October 2018 has imposed additional tasks on the transmission system operators (TSOs) directly concerned and also on neighbouring TSOs, notably as regards congestion management. Bidding zones are areas where a wholesale electricity market price applies, and the AT-DE/LU separation resulted in increased demand for intraday cross-border capacity at the Austrian-Swiss border. The two TSCNET shareholders APG from Austria and Swissgrid, the TSO from Switzerland, have reacted to this changed market situation and introduced automated, platform-based intraday capacity allocation.

A border-specific solution was necessary because the Austrian-Swiss border cannot be integrated into Single Intraday Coupling (SIDC, originally introduced as XBID in 2018). Therefore, the intraday allocation of cross-border capacities is still carried out via explicit allocations, but now in an automated process. On 23 September 2020, with the first delivery on 24 September, telephone allocation was switched to a platform-based allocation. The IT platform used – Intraday Capacity Service (ICS) – allocates capacities in accordance with the “first come, first served” principle. After almost two weeks of automated allocation, the two TSOs consider the new, easier intraday trading procedure a success. Swissgrid has already been applying this more efficient allocation of cross-border volume on the Swiss borders with Germany and France.

APG and Swissgrid have successfully introduced automated intraday capacity allocation at the Austrian-Swiss border (picture of the Austrian-Swiss frontier at Diepoldsau/Lustenau: Rikki Mitterer on Wikimedia Commons, CC BY-SA 4.0)

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Tunnel drilling for last section of the Nant de Drance connection

03.10.2020

The Nant de Drance pumped storage power plant in the Swiss canton of Valais is one of the most powerful power plants of its kind in Europe, generating around 2.5bn kWh per year, when it goes fully operational in 2021. The plant has been commissioned successively in sections in recent years. TSCNET shareholder Swissgrid, the Swiss transmission system operator (TSO), is responsible for connecting the power plant to the extra-high voltage grid and for transmitting the hydropower to urban areas in Switzerland. Two of the three sections of the extra-high voltage link to Nant de Drance – an underground cable of 6.5 kilometres between the power station and the Châtelard substation via the access tunnel of the plant and an overhead line of 12.5 kilometres between the Châtelard and La Bâtiaz substations – have been in operation since the end of November 2018.

Tunnel boring has now begun for the third and final section between the substations of La Bâtiaz and Le Verney, which belongs to the municipality of Martigny. The mini tunnel boring machine, weighing around 60 tonnes, was traditionally given a female name on 2 October 2020 at the construction site in Le Verney and will in future be known as Giorgia. Shortly after its christening, it was lowered into the shaft, where it will take around eight months to dig and secure the tunnel between the substations. The tunnel will have a diameter of 2.5m and is dug 12 to 20m deep into the ground. Giorgia is controlled entirely from the control centre at the construction site in Le Verney.

Construction of the underground cable link commenced in June 2020 with the excavation of the shaft at Le Verney and will take two years. The shaft at La Bâtiaz will be dug at the same time as tunnelling work. The finishing work in the tunnel will follow from summer 2021, after which the gantry to connect the Nant de Drance link to the 380kV Chamoson-Romanel overhead line in Le Verney will be built. Finally, the cables will be laid in the tunnel. Commissioning of the 1.2km long underground line is scheduled for 2022. Nant de Drance is already now connected to the transmission grid even before the last section of the link is commissioned: An interim solution was introduced in 2019 by increasing the voltage of one of the two overhead lines between La Bâtiaz and Le Rosel to 380kV.

Swissgrid has started tunnel drilling for the final section of the connection of Nant de Drance to the national 380kV grid (picture: Swissgrid)

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New power line for west-central Switzerland

17.09.2020

Switzerland’s national sustainable energy strategy and the resulting growth in hydroelectricity generation in the cantons of Berne, Valais, and Ticino require a significant increase in electricity transmission capacities, particularly to transport green energy to the Swiss Central Plateau and to ensure long-term security of supply throughout the country. This requires the upgrade of existing lines to 380kV and the construction of new high-capacity lines. One example of this is the 220kV line from Innertkirchen in the district of Interlaken-Oberhasli (canton of Bern) to Ulrichen/Obergoms in the district of Goms (canton of Valais), most parts of which are over 60 years old.

To maintain a secure connection between Haslital and Obergoms in the future, the Swiss transmission system operator (TSO) Swissgrid has developed various planning corridors for the construction of a new extra-high voltage line and submitted them to the Swiss Federal Office of Energy (FOE). The TSCNET shareholder has defined three main corridors, some of which include sub-corridors: The first option is a pure overhead line, which crosses high alpine terrain in parts. The second is partial cabling. Here, the middle section is implemented as underground cables, mainly in existing tunnels up to Obergoms. The third variant provides for underground cabling almost exclusively. Either in a new, yet to be built tunnel and then, as in the second alternative, in largely existing tunnels – or in the proposed multifunctional Grimsel Tunnel (envisaged for rail transport and power transmission). If the tunnel is used, the corridor variants for the last section to Ulrichen are possible as overhead line or underground cable        .

Each of the submitted options has specific advantages and disadvantages in terms of spatial planning, environment, technology, and economic efficiency. What they all have in common is the relief of settlements in the affected area, where overhead lines currently run partly through villages. The FOE is now discussing and evaluating the planning corridors. Its recommendation will then be submitted to public consultation, and the Swiss Federal Council is expected to determine the planning corridor and transmission technology between Innertkirchen and Ulrichen at the end of 2022.

Swissgrid has designed and submitted corridor variants for the new Innertkirchen-Ulrichen 380kV line (picture of the existing line: Swissgrid)

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Power outage in July in Valais cleared up

09.09.2020

As in many European countries, the Swiss transmission grid already today – at the beginning of the energy transition – has structural bottlenecks. Here, as elsewhere, these must be eliminated to increase security of supply and maintain it in the long term. Tense grid situations may pose problems to the connected system, as the Swiss transmission system operator (TSO) Swissgrid experienced on 17 July 2020, when the protection equipment of the 220kV grid node Creux de Chippis was accidentally tripped, which in the further course of events led to supply interruptions in the Valais distribution grid. The TSCNET shareholder immediately initiated extensive investigations into the event, the results of which have now been transparently communicated.

An extremely complex chain of technical and human factors is behind the Chippis incident. First the technical aspects: The transmission grid capacities in the region around Chippis are insufficient in summer due to the high generation of Alpine hydroelectric power plants. Because of this, Swissgrid for some time now had to completely disconnect the transmission grid in the Mörel substation in east-west direction for around 15 weeks a year to guarantee grid security and transmission capacities in the region. This reduces fault tolerance in the regional transmission system. In addition, several extension projects are currently being implemented in the Chippis area, which made adjustments to the operation of the Chippis substation necessary. These settings – also affecting the protection settings of the system – were carried out by the contracted service provider in December 2019.

As regards the human factor in the chain of events, necessary and scheduled tests of protection parameters were performed by a contracted specialised company in the Chippis substation on 17 July. During these tests, the system was not put into revision mode, which is why the system protection function unintentionally detected the test signal. This triggered the so-called busbar protection. The switchgear in the Chippis substation was subsequently disconnected and, due to the special grid situation, the switchgears in Stalden, Bitsch, Zermeiggern, and Mörel were also affected by the voltage loss, leading to a regional supply interruption in the distribution system.

The result of this combination of occurrences was a power failure in 60 municipalities in the district of Sierre and in most of the Upper Valais. After one hour, all affected switchgear and Swissgrid lines were back in regular operation. Thanks to the good cooperation between Swissgrid and the concerned distribution system operators (DSOs) of the lower voltage levels, electricity supply was gradually resumed and after less than two hours, almost all customers were back on power. Adrian Häsler, Head of Grid Infrastructure at Swissgrid, classifies she supply disruption in Valais as “an extremely rare occurrence”, but nevertheless apologises to those affected. And though the tests themselves were not negligent, the findings from the incident are incorporated into the company’s training and education of internal and external experts. Häsler also emphasises that Swissgrid drew attention to the bottlenecks in Valais some time ago: “Incidentally, we recognised these grid congestion problems in the context of ‘Strategic Grid 2025’, the TSO’s ambitious grid modernisation and extension plan, and addressed them in 2015. The grid expansion as planned by Swissgrid is essential to maintain the long-term security of supply.”

Swissgrid is investigating the voltage loss in the switchgear of the Chippis substation in Valais on 17 July (picture: Swissgrid)

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Successful trial run for Equigy

09.09.2020

Fluctuations in the transmission grid are an emerging concern for European transmission system operators (TSOs) as volatile renewable generation gains in importance with the energy transition and more and more large scale power plants that stabilise the grid are being decommissioned – resulting in a considerable loss of reactive power. TSOs need to take remedial action involving intelligent technologies and supported by small, decentralised energy sources to keep production and consumption in balance. One such solution for the provision of primary control energy is the crowd balancing platform Equigy launched by the Swiss TSCNET shareholder Swissgrid in cooperation with further TSCNET shareholder TenneT, the Dutch-German TSO, and the Italian TSO Terna.

Kick-off for Equigy was in April 2020 and the objective is a new European standard allowing the participating – and possibly more – TSOs to collaborate for promotion and improvement of the renewable energy market. The innovative platform is based on blockchain technology and the Internet of Things to enable the integration of small, decentralised units such as home battery storage systems, photovoltaic systems, small-scale hydropower systems, heat pumps or even electric cars into the balancing energy market. The pilot project now has reached its first milestone: Together with Alpiq, a Swiss energy services provider and electricity producer, Swissgrid has successfully tested the process of calling up primary control power through the balancing platform. The test employed a 1.2MW battery as a flexible energy resource. Alpiq has assumed the role of commercial aggregator, linking the technical aggregator, which controls the controllable resources, with Swissgrid.

In particular, the call-up of primary control energy included the registration of flexible resources, submission of offers and awarding of bids, as well as real-time monitoring of data exchange between Alpiq and Swissgrid. The test has proven that a blockchain can support the process of providing primary control power and that aggregators or storage owners with backend systems can integrate the blockchain interfaces. The Equigy trial run has clearly indicated the potential of blockchain solutions for the future support of business processes in the field of primary control energy – this is a fundamental finding and a significant step forward. The next steps concern the evaluation of possible business models among the participating partners.

The blockchain-based crowd balancing platform Equigy by Swissgrid, TenneT, and Terna passed trial run

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Swissgrid provides background information

20.08.2020

Our secure power supply needs a stable and well-maintained grid, and the energy transition requires a substantial expansion of the transmission grid in particular. The Swiss power transmission system operator (TSO) Swissgrid is following the “Strategic Grid 2025” project and is now providing a wealth of information on the financial aspects in a background article.

The construction costs of a new line depended not only on the site and the required capacity, but above all on the chosen line technology. According to the experience of Swissgrid experts, an underground cable costs twice as much as an overhead line in the best case and ten times as much in the worst case. Over the period of use, underground cabling is also more expensive to maintain than overhead lines, and repairing damage is more complex and takes much longer. However, the decision on the choice of the respective variant would be made by the authorities. In each individual case, the “view of the big picture” is crucial. In addition, the TSCNET shareholder offers the 20-page German-language brochure “Overhead line and underground cabling” for free download, which provides an excellent insight into construction methods and the basis for decision-making in the Swiss electricity transmission grid.

Swissgrid ensures transparency in costs and decision-making process (illustration using graphics of Swissgrid)

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Swissgrid analyses supply disruption in Valais

22.07.2020

On Friday, 17 July, the Swiss transmission system operator (TSO) Swissgrid carried out check-operations concerning the extension of the 220kV switchgear in the Chippis substation in the canton of Valais. At 4.23 p.m., the protection equipment of the 220kV grid node Creux de Chippis was accidentally tripped, causing the switchgear to lose voltage. As a result of the technical failure at Chippis, the switchgear of the substations in Stalden, Bitsch, and Mörel were also affected by the voltage drop, which led to a regional supply interruption in the distribution system.

The result was a one-hour power outage in a total of 60 municipalities with around 112,000 households as well as trade and industry in the Swiss Sierre district and the largest part of the Upper Valais. By 5.23 p.m., all affected switchgear and lines of the TSCNET shareholder were back in regular operation. Thanks to the good cooperation between Swissgrid and the five affected distribution system operators (DSOs) of the lower voltage levels, it was possible to gradually restore the electricity supply from 5 pm onwards. By 6.15p.m. almost all customers were back on power. Swissgrid immediately initiated a detailed investigation of the incident, which is currently in progress.

Swissgrid is investigating the voltage loss in the switchgear of the Chippis substation in Valais on 17 July (picture: Swissgrid)

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Swissgrid responds to revised legislation

15.07.2020

With the national “Energy Strategy 2050”, the Swiss electorate decided in 2017 to promote renewable energies. To extend the duration of the correlating support measures, create planning security for the energy market, and eventually achieve Switzerland’s climate policy goals, the Swiss Federal Council has developed a revision of the national Energy Act (“Energiegesetz”). The Swiss transmission system operator (TSO) Swissgrid appreciates that the Federal Council intends to create more incentives for the expansion of domestic renewable energies while at the same time ensuring long-term security of supply.

However, the TSCNET shareholder considers that the legal framework must also contribute to integrating renewable energies into the overall system. According to Swissgrid, this is the current situation in Switzerland: The combination of the absence of an electricity agreement with the EU, a significant increase in renewable energy with volatile generation, and the sluggish expansion of the grid affects the operation of the transmission system. Because even today, the grid expansion is not keeping pace with that of the renewables.

To meet the goals of the “Energy Strategy 2050”, it must first be ensured that approval procedures for grid projects are consistently optimised and accelerated. Secondly, innovative solutions for load management are needed to generate flexibility and provide frequency services to the transmission grid. The crowd balancing platform Equigy – a cooperation of Swissgrid, TSCNET shareholder TenneT, the Dutch-German TSO, and the Italian TSO Terna – is one example of such a solution. Thirdly, an electricity agreement between Switzerland and the EU is essential, since import and export capacity will make an important contribution to Switzerland’s supply security given the significant expansion of renewable energies. Finally, Swissgrid considers the non-discriminatory availability, quality, and transparency of data to be increasingly important for secure grid operation. This requires a legal basis for regulating data transfer between TSOs, distribution system operators (DSOs), storage and power plant operators, and other parties involved.

Swissgrid comments on the revision of the national Energy Act by the Swiss Federal Council (illustration based on a picture of Lac de Moiry in Valais, Fotoauge, Pixabay)

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Construction permit for Pradella-La Punt

13.07.2020

As the extra-high voltage line in the Swiss Engadine between Pradella and La Punt constitutes a bottleneck in the Swiss and pan-European transmission system, the Swiss transmission system operator (TSO) Swissgrid has long aimed to increase its transmission capacity to 2 x 380kV. This will improve import capacity and security of supply in the canton of Graubünden and facilitate the transport of Engadine hydropower. The project is part of the “Strategic Grid 2025”, Swissgrid’s ambitious modernisation and expansion plan.

The Swiss Federal Inspectorate for Heavy Current Installations (Eidgenössisches Starkstrominspektorat-ESTI) now has approved the reinforcement and new construction of pylons between Pradella and La Punt. Swissgrid has already refurbished the pylon foundations in the past two years, so that work can commence soon. Approximately 3500 tonnes of steel will be needed to upgrade the around 50-kilometre-long overhead line. The construction will be carried out in two sections and is expected to be completed by the end of 2022.

To reduce the overall environmental impact in the region, Swissgrid is supporting a local grid operator in replacing a 60kV overhead line with a 110kV underground cable. As a result, 1100 pylons will be disappearing from the landscape.

Swissgrid can start with the 2 x 380kV upgrade of the Pradella-La Punt line (picture: Swissgrid)

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