Electricity from four power stations
Impressive: One of the three storage pumps at the Ferrera power plant.
Complex complete renovation of the Hinterrhein power stations
Kraftwerke Hinterrhein AG (KHR) operates the largest hydroelectric power plant combination in the Swiss canton of Graubünden. With a three-stage plant group, KHR has been producing an annual average of around 1,400 GWh of environmentally friendly electricity for 50 years. In recent years, the plants have been completely renovated, which was a major challenge due to the complexity of the project, the schedule and the external conditions alone.
After decades of planning and negotiations, Kraftwerke Hinterrhein AG was founded in 1956 on the basis of a treaty concluded between Switzerland and Italy in 1949. This led to one of the largest Swiss construction projects of the 1950s and 1960s: With an investment volume of over CHF 600 million, around 37 kilometres of new roads and paths, ten cable cars, 13 stream catchments, five dams, 59 kilometres of tunnels and shafts, and three power stations were built in just six years, and almost 110 kilometres of transmission lines were laid. In 1959, at the height of the construction work, almost 3,400 people were employed on the building sites.
Important power supply node
The power plant combination with the Ferrera, Bärenburg and Sils power stations has been in operation since September 1963. In 1968, the Thusis power plant was commissioned, which utilizes the residual water remaining in the Hinterrhein. With an installed capacity of 650 MW, the turbines harness the power of the water via three power plant stages from the Lago di Lei reservoir, located at 1,931 metres above sea level, to 667 metres above sea level in Sils. The cavern power station in Ferrera has a pumping capacity of 90 MW, enabling the water that has already been turbined once to be pumped back from the equalising reservoir or the reservoir in Sufers to Lago di Lei.
The dam of the Valle di Lei seasonal reservoir is a superlative structure: 840,000 m3 of concrete were used in the dam wall with a crest length of 690 metres, and with a capacity of 197 million m3, the reservoir is the third largest in Switzerland. Equally impressive are the 220/380 kV switchgear installations of swissgrid in Sils: almost 25 per cent of the electricity consumed in Switzerland and around 30 per cent of the electrical energy generated from hydropower in Switzerland flows through these installations. Sils is therefore an important hub in the Swiss and European electricity grid.
Complete renovation after 50 years
"After 50 years of operation, many components of our infrastructure had reached the end of their maximum service life," says Guido Conrad, Director of KHR, explaining the motivation behind the complete renovation of the facilities, which required an investment of around CHF 300 million. As the capacity of the plants will not be increased, no change to the concession was necessary for the refurbishment: "Thanks to the use of state-of-the-art technologies, the efficiency of the production facilities can still be increased," says Guido Conrad. "Replacing the old turbine runners with new ones alone will improve efficiency by around three per cent."
Environmentally friendly refurbishment – minimal disruption to operations
While comparable large-scale plants are often renovated in stages, KHR opted for a complete overhaul with minimal operational interruptions. "This was certainly one of the most challenging tasks," explains Guido Conrad, "because in order to access the water-side parts of the plant, all the reservoirs and basins had to be emptied." It was important to KHR that the process was extremely environmentally friendly, which is why extensive measures were taken at the same time to protect plants, animals and microorganisms. Due to the water conditions, most of the work took place during the winter months, "even though the external conditions in the mountains are not exactly ideal," says Guido Conrad, describing the schedule, and adds: "However, for two years we only had to expect reduced electricity production in winter, which amounted to only about 12 per cent of our annual production over the entire renovation project phase."
"Rittmeyer is a project partner on equal terms."
Complete control technology renewed
However, it is not only the 13 large KHR machine sets that are being renewed and revised, but also the entire control technology. The overall project was divided into around 100 lots and put out to public tender. "Rittmeyer submitted the most favourable bid for the renewal of the control technology and also impressed with its excellent references," recalls Guido Conrad.
During normal operation, all Hinterrhein power plant systems are now monitored and controlled from the central control center in Sils. This is based on a distributed RITOP overall system with redundant client/server subsystems at each of the four power plant locations. Over 150 RIFLEX M1 automation and remote control systems automate the 21 machine groups and the systems in 26 external objects. More than 200 switch cabinet panels, all manufactured at the Rittmeyer plant in Baar, now house the machine controls, turbine governors, voltage regulators and electrical protection. "Wherever possible, the systems at all power plant locations are identically constructed," says Guido Conrad, describing the implementation. This not only simplifies spare parts management, but also reduces operating and maintenance costs.
On schedule
More than two-thirds of the construction phase has been completed, with most of the work on schedule. "The demands on the control engineers are particularly high. They always come into play at the very end and have to compensate for any delays that arise during the conversion of the systems," says Guido Conrad. The complexity of the overall project therefore places extraordinary demands on the project management and system integration expertise, in addition to the purely technical aspects. Guido Conrad is impressed by the collaboration: "Rittmeyer treats us as an equal project partner, always open, fair and with a high level of technical expertise."
All work will be completed by mid-2016 – and the Hinterrhein power plants, equipped with Rittmeyer control technology, will enter their next half-century of safe operation.
Image credit: Hinterrhein power stations
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