The Chaira hydroelectric power station
Image: Edal Anton Lefterov, Wikimedia Commons, CC BY-SA 3.0
Bulgarian state-owned company Natsionalna Elektricheska Kompania EAD (NEK EAD) has signed a memorandum of understanding with Toshiba International Europe Ltd., the British subsidiary of Japan’s Toshiba Corp., to restart operations of the Chaira pumped storage hydropower plant.
The facility is the largest of its kind in Southeastern Europe and is located in the Rhodope Mountains near the town of Devin. The installation was commissioned in phases between 1995 and 2010. The plant is equipped with four reversible Francis pump turbines, each with a capacity of 216 MW in generation mode and 197 MW in pump mode.
Units 1 and 2 were commissioned in 1995, making Chaira the largest pumped storage facility in South East Europe at the time. Units 3 and 4 were subsequently commissioned in 1999, completing the four-unit configuration.
“The Chaira Pumped Storage Hydroelectric Power Plant (PSHPP), the country’s largest, has an installed capacity of 864 MW across four units. However, due to aging infrastructure, some units are currently out of service, underscoring the urgent need for comprehensive rehabilitation and optimized plant-wide operations,” Toshiba said in a statement.
The plant was shut down in March 2022 after a serious turbine accident during post-rehabilitation testing of Unit 4. The Bulgarian Ministry of Energy stated that the main cause was material fatigue, combined with the original turbine design and cavitation effects.
“Toshiba has already been commissioned to carry out repair work on Unit 1 and will also carry out studies and provide technical support for the plant as a whole, including operational and maintenance support for Units 2, 3 and 4, as well as recommendations to improve the reliability and efficiency of key equipment such as pump turbines and generators,” the company added.
Toshiba supplied the turbine and generator with pumped storage for Unit 1 of the Chaira plant in 1994. His involvement later expanded to all four units. It also supplied four generators with a combined power of 940 MVA.
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