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History meets modern engineering

A facelift assuring the future operation of equipment in run-of-river power plants at Ryburg-Schwörstadt and Wyhlen for coming decades.

Top right: Ryburg-Schwörstadt hydro power station / Constructed: 1927 – 1931 / Turbine types: 4 Kaplan turbines / Output: 120 MW / Annual production: 760 million kWh / Weir length: 111 m / Weir control gates: each is 24 m wide, 12.5 m high, and up to 140 t in weight

Bottom left: Wyhlen hydro power station / Constructed: 1908 – 1912 / Modernised: 1990 – 1994 / Turbine types: 6 Straflo and 5 Francis turbines / Output: 38.5 MW / Annual production: 255 million kWh / Weir length: 212 m / Weir control gates: each is 20 m wide, 9 m high, approx 100 t in weight

Modular, cycled power-supply and converter technologies have already been successfully utilised for several years now, in various market segments, such as in IT, in automation and in the field of telecoms.

In these market segments, the engineers in charge have taken the bold step of migrating to innovative power-supply systems – promoting their introduction to industry. The need to provide for critical-function business processes in a reliable way is fully realised, thanks to the advantages of this technology, which includes high availability, flexibility, simple maintenance and optimised efficiency. Consequently, this was a logical step to take, based on limitless configuration options.

In conventional industrial applications, it has taken a very long time for this modern technology to establish itself. In particular, the power station sector, which is rather conservative in its approach, has been dominated by long-inherited thyristor technology. Until recently, that is.

The operators of the types of power station we are concerned with have applied, and are still applying, their own versions of technical principles for the purpose of supplying the power station’s “own power requirements”.

The corresponding specifications, most of which were written decades ago, are based on the thyristor technology that was prevalent when those specifications were introduced. Consequently, there has been a time-lag in the introduction of modern system designs and in the process of innovative technologies penetrating this sector of industry. It’s taken this long. The project we’re describing here is an impressive illustration of a power station operator’s change in attitude towards innovative, modular power supply systems – once given cost-neutral, competent technical advice.

Picture Claus Kirmaier
Claus Kirmaier, Director of Southern Branch of BENNING

“Because BENNING produces both thyristor technology and also highly modern, cycled plant in a modular design, we had an impartial position in terms of cost and technology, when it came to advising the operator.”

Composition of redundant power supply system
Highly integrated power supply system with redundancy, to provide secure supply of power to turbine buildings at Wyhlen hydro power station
5 generators in a row
View of generator shop at Wyhlen river-run hydro power station.

Energiedienst Holding AG, based in Laufenburg, Switzerland are the owners and operators of the power stations. They started work at the beginning of 2019 on the initial planning for the modernisation and replacement of the on-site power supply systems for their fully automated run-of-river hydro power stations in Wyhlen and in Ryburg-Schwörstadt, where the plant managers are responsible for power supply.

Highest priority goes to availability

In this context, it’s a maximum priority to have an on-site power supply, that is reliable, to cover the power station’s crucial operating requirements. A seamless data logging record over a wide range of measurement points provides the basis for all open-loop and closed-loop interventions over a massive range of parts internal to the power station, most crucially including its generators.

At that stage, it was more than 25 years ago that the power supply systems of these power stations, which had been commissioned between 1908 and 1931 in the Hochrhein (literally: “Upper Rhine”) region, had last been modernised. Accordingly, it was extremely likely that something would fail within the next few years.

It’s essential for the Wyhlen power station to have a reliable power supply for the Francis machinery which is employed, when required, to back up the more recent Straflo turbines. Any failure in the supply of power could lead, in the worst case, and that also goes for the Ryburg-Schwörstadt power station, to serious damage to these irreplaceable, historic generators which have been producing so much power output for so many decades.

In June 2019, in order to avoid production shutdown and all of the entailed consequential costs in the run-of-river hydro power stations, a corresponding outsourcing specification was published. The investment plan embraced by the Energiedienst company, as the operator, was to secure continued power station operation even in the event of a grid failure. The objectives included achieving remote, 24/7 monitored and automated, and hence cost-optimised, operation for its power stations.

Planning and expert assessment

Also in June 2019, there was the first onsite meeting to review local conditions. Considerations that required discussion included looking at the ways & means of updating the “state of the art” systems in place at the time.

This was followed up by refining the outsourcing specification, in July 2019, with a range of questions from potential providers, and these questions themselves would allow the client to assess the pros and cons of modern, cycled technology as compared with the specified conventional, thyristor-based equipment.

BENNING had already submitted an initial quote by the end of July 2019. There were, in fact, two quotes. Because although the planning engineers were already convinced that the specified requirements could be better fulfilled using modern, cycled technology, a further alternative was also duly submitted to cover the thyristor equipment that had been specified in the first place.

Because BENNING’s product catalogue also includes conventional technology, alongside the modular cycled units it promotes, the power station operator received the valuable option of be-nefitting from advice that was inherently cost-neutral and technology-neutral.

The next step was to have a comprehensive comparison and assessment of the respective types of equipment taking account of all of the relevant criteria. They considered not only maximum availability but also user-friendliness and all of the cost-related issues. The Energiedienst company was insistent on maximum sustainability of entire power supply system in terms of environmental protection and ecology.

Composition of a controller for regulation of water intake for a turbine
Section view of controller for regulation of water intake for a turbine at the Ryburg-Schwörstadt power station
Power supply system - 3 elements
Power supply system for 40-megawatt switching system

Inspired by the advantages

Ultimately, the customers found that they were inspired by the advantages of the highly modern and modular technology that was available. Accordingly, the order for the project on the Wyhlen run-of-river power station was awarded in December 2019, whilst the go-ahead for the Ryburg-Schwörstadt power station was awarded in January 2020. The operators’ decision was swayed not only by the maximised availability obtained thanks to the systems’ being designed with N+1redundancy. There was more than that in the balance; Energiedienst appreciated the substantial operational advantages inherent in using standardised components over a number of different power station sites.

The inherent simplicity of immediate response from in-house engineers, with hot plug/swap capability and the employed automatic module configuration feature, also helped to influence the decision. Accordingly, duty staff will have an easier job thanks to the plants being managed in a closed-loop control, with greatly simplified handling of components in the event of any fault arising, but also with regard to handling and transporting of any components. As far as the industrial department was concerned, it was of crucial value to have 100% integration into the infrastructure on the power station side, together with equipment automation. The solution to this objective turned out to be surprisingly straightforward. Thanks to the versatile configuration of the modular power supply systems’ data interfaces, all of the historically entailed range of interfaces in the power station’s control technology exhibited versatility and comprehensiveness of control in operation.

Product diversity, but still “tailor-made”

As a globally established manufacturer of AC and DC power supply systems, BENNING has very high product diversity and is able to develop and apply individual, custom solutions at short notice. This means that the customer always receives the solution that is ideal for him – in technical terms and according to design criteria.

In the context of this project, for example, not only were the thyristor units (originally specified by the planner) for the required 220 VDC and 48 VDC voltage levels replaced by cycled modules of the most modern design; also, thanks to BENNING’s expert recommendation, the power stations did not receive the addition of the conventional 48 VDC rectifiers but only the modular type 3000 IDC DC/DC converters that were based on 220 VDC on the input side. Thanks to using these modular 19 inch systems, it was possible to achieve a great reduction in the energy loss caused by the voltage step down.

These DC/DC converters simultaneously provide (even in the event of a grid failure) a 48 VDC power supply which remains constant at all times, specifically for the legacy Francis generators, which are quite sensitive.

BENNING redundancy distribution - 2 elements
Distribution with power-feed redundancy to protect energy supply for the Francis turbine shed at the Wyhlen power station

The scope of supply also includes highly automated distributon with a wide range of motorised power circuit breaker which enable the power stations to be controlled remotely from the central console. The capability of on/off switching for individual power station sections and also the fact that they can be coupled, is not only important for normal operation but also enables the optimum emergency mode if a supply issue arises, such as a comprehensive blackout.

When an emergency supply issue does arise, the energy stored in the battery systems that come supplied as standard by BENNING as system components will then provide the reserve power required in order to guarantee fully uninterrupted operation of all items of plant in the event of a grid failure.

At the same time, the accumulators in the power stations make it possible to carry out a “black start”. In the event of a comprehensive grid failure or in the event of a simultaneous power station shutdown, the regulation of the weir could carry on with battery power for only a short bridging period.

In order to be able to monitor the flow of water through the control gates at all times, however, it’s essential for these components to have the necessary power supply at all times. In the first instance, the “start-up power” required in order to initiate fully-independent island mode can be drawn from the battery systems; and once the mighty turbines are spinning, the corresponding power is of course available as a by-product.

In BENNING’s capacity as the system partner for Energiedienst, it also provided the installation service – in addition to manufacture. The scope of services includes an assessment for grid and selectivity, extraction of old systems, transporting the new equipment to site, installation, cabling and commissioning.

BENNING’s expertly trained staff are able to provide support with “AuS” (corresponds to Work-ing Live) issues. Appropriately trained staff can ensure that any power station’s consumers that must be kept running are switched over, without interruption, to the newly installed plant systems.

19" BENNING Modul TEBECHOP - single
19” DC/DC converter module with five TEBECHOP modules, 3000 IDC

Energiedienst Holding AG

The head office of Energiedienst Holding AG is in Laufenburg, Switzerland.

The sites where power stations in the Hochrhein region are located include Wyhlen and Ryburg-Schwörstadt.

Energiedienst operates a total of 21 hydro power stations, some larger, some smaller, and also collaborates with its subsidiary – ED Netze GmbH – as the grid operator.

Portrait Marco Gerspach
Marco Gerspach, Engineer in energy management (B. Eng.) Power station engineering, Energiedienst

“Thanks to our partnership with BENNING, we have the facility to team up with a reliable service provider which can boast the ideal product portfolio.”

Left: Thanks to motorised output switching in the distribution systems supplied by BENNING, there’s fully automated management of operations from the control console at all of the power stations’ system-related voltage levels

Middle: 220 V rectifier system in the transformer house – facility for coupling to the generators, at the Wyhlen hydro power station

Right: Distribution of consumers Francis generators


The customer’s decision to select modern, modular power-supply systems was greatly influenced by the opportunity to receive cost-neutral, credible, competent information on the advantages and the benefits of this solution as compared with conventional monobloc systems. Together with the opportunity to ask whatever questions they needed.

Energiedienst’s much trusted partnership with BENNING meant they had the facility to work with a reliable service provider who can offer the comprehensive product portfolio to fully satisfy all of the clients requirements. Efficient manufacture and a smoothly completed installation are assured, thanks to the decades of experience and expertise in the field of hardware design, quality management and installation planning.

This will be completed with commissioning – planned for July 2020.

And this is how the Energiedienst’s run-of-river hydro power stations at Wyhlen and Ryburg-Schwörstadt are going to continue to provide a reliable supply of power, around the clock, making a major contribution to the move towards sustainable energy.

Further Information

contact: Claus Kirmaier
telephone: +49 8332 936363

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