Pump units at Belmeken RHPP commissioned
We commissioned the fourth pump unit as part of the revitalization project at three HPPs—Belmeken RHPP, Sestrimo HPP, and Momina Klisura HPP—with a combined generation capacity of 739 MW. These cascade power plants are vital components of the Bulgarian power system, and the project is implemented in three phases to guarantee the availability of at least one unit at each plant for uninterrupted generation at all times.
At the tail-end of 2022, we successfully commissioned a pump unit at Belmeken RHPP, as part of the ongoing revitalization project of three hydropower plants with the Bulgarian Natsionalna Elektricheska Kompania NEK EAD. The first and second stages of the reconstruction involved two units each, and the fifth unit is part of the third phase, currently undergoing testing with plans for commercial operation by the end of 2023.
The revitalization included the replacement of the control system, excitation system, turbine regulation system, circuit breakers, hydraulic units, nozzles, servomotors for hydro-mechanical equipment, etc. Distinct features of the pump unit represented a challenge during revitalization.
This unique 83 MVA unit features a vertical synchronous generator-motor design. In generator mode, it is powered by a Pelton turbine, while in motor mode, it drives a five-stage centrifugal pump with a maximum pumping height of about 750 m and a flow rate of 6.9 m3/s, consuming approximately 55 MW. This functionality is achieved through a specific coupling mechanism between two coaxial shafts (turbine and pump) and a total of seven bearings, two of which are combined (support and lead). The design allows the pump mode to be powered by a Pelton turbine.
Within this exceptionally technically challenging and organizationally complex project we also undertook coordination of all construction site activities, managed the entire project and coordinated the development of the final and as-built designs.