Refurbishing Lernbo

23 September 2008

A joint venture of Austrian firm Kössler and Germany’s Lloyd Dynamowerke is undertaking refurbishment work at the Lernbo hydro power project in Sweden

After the successful recommissioning of the new turbine, generator and electrical equipment in its Ludvika project in 2007, Västerbergslagens Kraft of Sweden decided to refurbish its Lernbo project to bring the plant in line with the latest safety and environmental requirements.

Similar to Ludvika, the goal is to install the new equipment in the existing power house while preserving the old structure as much as possible.

The owner of the plant is Västerbergslagens Kraft AB, with 58% owned by Vattenfall AB and 42% by the Ludvika community. The scheme is located on the Kolbäcksån stream, close to the centre of Smedjebacken city. It was one of the largest in Sweden when it was completed in 1899 and swung into commercial operation.

In 1912 one unit was changed to a 60Hz double Francis machine. While in 1944 the remaining unit was replaced with a 50Hz double Francis. The 2MW and 3MW machines were connected to a 10kV line.

After over 60 years of service significant performance, safety and environmental improvements have been implemented. The new turbines and generators will increase the efficiency of the plant and will increase the annual generation from 22.9GWh to 28GWh – almost 25% increase of annual generation. Västerbergslagens AB is certified for Swedish electrical certificates for 28GWh/yr.

Austrian firm Kössler was awarded the contract for refurbishment based on its technical solution. It will supply two Kaplan S- turbines with direct driven medium voltage synchronous generators from LDW (Lloyd Dynamowerke in Bremen, Germany) and install them in the existing structure.

The scope of supply includes:

• Two Kaplan S- turbines (3.5MW each).

• Two 4.2MVA synchronous generators.

• New switchgear and control panel.

• New control system for the intake gates.

• Expansion tower repair.

• Installation of new local power.

• Installation of two new overhead cranes.

• New cooling and heating system.

• Installation of an accumulator tank, to save the surplus from the generator bearings, and to heat the building.

Much of the existing structure below the ground floor has to be demolished. It will be a challenge for the technicians, project manager and civil constructor to rebuild the powerhouse in the required configuration for the erection of the new equipment. Civil work started in January 2008 and will be completed in September 2008. The turbines will be delivered by the end of March 2009, and commercial operation is planned for October 2009.

The operator plans to run the units at the highest conversion efficiency. On average both turbines at Lernbo are in operation 17 hours a day (05:00-22:00 Monday to Friday) all year round, resulting in 4350 hours each year. The energy produced in Lernbo is sold on the Nordic spot market and the electrical certificate is sold on the market.

The production is based on a weekly operating plan. The operating plan is made by VB-Kraft AB and provided to Vattenfall AB’s production planning department. The same operating plan has been applied to the Ludvika hydro power project.

The total cost of the project for Lernbo is approximately 80M SEK (US$12.7M). This investment is being made in part to increase environmental and safety requirements by:

• Using environmentally friendly oil and lubricants.

• Installing an oil-free runner hub.

• Incorporating greaseless bearings for guide vanes and wicket gates.

• Installing a safe system for separating hydraulic oil.

• Recovering the heat from the generators to be stored in the accumulator tank and distributed to different heaters.

The authors are Roger Sandgren, Managing Director Västerbergslagens Kraft AB, and Karl Henninger, Project Manager, Kössler Ges.m.b.H.

Technical data of Lernbo hydro power plant

Manufacturer - Kössler - a Voith and Siemens company
Type - Kaplan S-type
Number of Units - 2
Runner diameter (m) - 1.70
Gross head (m) - 27.23
Speed (rpm) - 428
Output (kW) - 3640

Manufacturer - Lloyd Dynamowerke Bremen
Type - Synchronous
Number of Units - 2
Voltage (kV) - 10.5
Flywheel (tons) - 5.0
Speed (rpm) - 428
Output (kVA) - 4200
Weight (tons) - 36

Inlet pipe Inlet pipe
Generators Generators

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