Mariborski otok power plant: the lowest lying in the riverbed
This pier type power plant is the lowest lying power plant in the Drava River Chain, located just outside of Maribor in the riverbed, exploiting the energy potential of the Drava River between the Fala HPP and the island in the Drava River.
It uses the 14,2 m available head and, following its refurbishment, annually generates 270 million kWh of energy with the net capacity of 60 MW.
The construction of the power plant had been planned prior to the World War II, but construction only began in 1942. The war caused the construction process to be drawn out considerably so that in May 1945 it was still only 30% completed. Despite a number of problems after the war, construction work continued and 1948 saw the commissioning of the first unit, with the second and third units beginning operation in 1953 and 1960.
The dam constructed for damming the Drava River created a 15,5 km long reservoir which reaches as far as the Fala HPP further upstream and contains 13,1 million m3 of water of which 2,1 million m3 can be used for the generation of electricity.
The dam structure contains three turbine piers placed between four spillways and a left and right bank building. Each of the turbine piers contains a vertical Kaplan turbine and a generator above it. A 10 kV switchyard and an area for two main transformers directly connected to 110 kV transmission lines leading towards the Pekre substation are located in the right bank building.
The four spillways, each 18,75 m wide, closed by the double plate hook gates, have a total spilling capacity of up to 5600 m3/s. The gates are suspended on Gall's chains and driven by electric hoists. A gantry crane is installed on the dam structure and is used for raising and lowering of heavy equipment and components.