On the river Nyvikelva in Røyrvik near the Swedish border, electricity provider Norsk Grønnkraft AS has built a high-pressure power station supplying electricity for 300 regional homes.

This performance is guaranteed by the gensets installed, consisting of a Francis turbine provided by the Norwegian hydropower specialist, Spetals Verk, and a high-grade synchronous generator from the Austrian manufacturer, Hitzinger. The Austro-Norwegian gensets have a 2.1 MW power rating.

With only 0.32 inhabitants per square Kilometre (0.12 per square mile), Røyrvik counts among Norway’s least densely populated communities. Røyrvik is part of the Børgefjell national park that spans four communities and borders on Sweden. The characteristic mountain ranges and a rich, untouched nature are prime features of the land. In view of sustainable nature and landscape protection, ecologically viable electricity generation within the region enjoys excellent public acceptance and public approval. This is why hydroelectric power generation has an elevated relevance in the Northwest of the Nord-Trøndelag province. As early as the 1960es and 1970es, big stations were built in this region. More recently, modern small-scale hydroelectric power plants were erected such as Havdalen and Svartvann, to name only two.

A GENSET WITH A TRACK RECORD
The most recent addition to the Norwegian grids was built on the river Nyvikelva in Røyrvik. It is part of the 38 hydroelectric plants that Norsk Grønnkraft AS operates in Norway. The firm is one of the countries two biggest operators and became part of the German Aquila Kapital holding company at  he end of 2014. Four or five years ago, Norsk Grønnkraft had started planning the small-scale hydroelectric unit on the Nyvikelva River. The contract for the electrical equipment was signed in March, 2014. The project saw completion in early May of 2015, when the plant was officially commissioned. Like for the Havdalen and Svartvann before, Spetals Verk provided the turbine, while the matching generator was supplied to the far north by the long-established Austrian manufacturer, Hitzinger. The tried and tested combination was once more to be installed in the new Nyvikelva power plant.

GRP IS TUBING MATERIAL OF CHOICE
The river Nyvikelva has a catchment area covering some 40 square kilometres (15 square miles) of the surrounding highlands. A flow rate of 3.0 m³/s can be utilized for electricity generation. The works water is guided to the power house through an 850 m (2,800 ft.) penstock that was completely laid underground. The pipes used are a glass fibre reinforced plastic piping system with a nominal dimension of DN1200. The power house is situated at an elevation of 460 m (1,500 ft). With its wooden face, it blends in with the surrounding natural environment. The heart of the plant inside the power house has been optimally adapted to the conditions on site. “This genset configuration is typical of and really without a viable alternative for the given combination of head and flow“, explains Magnus Jonassen, general manager of Spetals Verk. Once again, this manufacturer’s time-tested Francis Common Blade turbine technology was installed.

OPTIMALLY ADAPTED
The turbine specialists from south-eastern Norway designed the turbine for a nominal flow of 3.0 m3/s and a 79.7 m (262 ft) head. The turbine’s rated power is 2,139 kW. The required voltage is supplied by a directly coupled synchronous generator from Hitzinger designed for a rated power of 2,350 kVA at 750 rpm. “Tradition, experience, quality and the unparalleled cost/performance ratio were the four most powerful motivators to finally decide in favour of a Hitzinger generator“, says Magnus Jonassen. There is also another significant benefit that has become something of a Hitzinger brand characteristic: Each individual generator is perfectly adapted and optimized to its operating environment. In particular, Hitzinger individually defines the proportional number of electrical sheets used in a machine so that the loss density is limited to a minimum. It is for this reason that the generators feature a singularly high efficiency. The generator specifically designed for the Nyvikelva hydroelectric power station achieves efficiency factors in excess of 97 % even under partial load. Relative to its 11 ton weight, the machine with its eight-pole design delivers a very high power output of 2,350 kVA.

PURPOSE-BUILT HEATER FACILITATES “COLD STARTUP”
As part of the specific configuration for this power station, the generator came equipped with a flywheel so it can cope better with possible pressure surge scenarios. The wheel has a 1,920 mm (6 ft 4 in) diameter and weighs about 3.5 tons. This results in a total torque of inertia of 1,900 kgm². The conceptual design of the generator took the harsh Scandinavian climate into account as well. Hitzinger engineers say they have installed a new and more powerful type of stationary heating system. It allows a problem-free restart after prolonged standstills in winter even in subarctic temperatures.

ELECTRICITY FOR 300 HOMES
Meanwhile, the Austro-Norwegian genset in the new Røyrvik power house has had several months to prove its high quality and reliability. Since last May, the new small-scale power station on the Nyvikelva River reliably feeds electricity to the Norsk Grønnkraft grid. On average, it supplies a total of some 6,8 GWh per year. This amount of electricity is sufficient to supply about 300 Norwegian homes. The yield exceeds the electricity required by the 500 residents of the sparsely populated national park community. For Norsk Grønnkraft AS as the operator, one significant aspect was that the power station is subsidised by the government following a certificates scheme similar to that in many other countries. This helped assure the plant’s economic feasibility. Thanks to the power station operator’s wealth of experience, it was possible in spite of tight economic pressure to assure a high-quality implementation, guaranteeing both reliable and effective operations of the plant for decades to come.