Chaira is located in the Rila mountains about 100 km southeast of Sofia, the capital city. The underground power plant contains four reversible Francis pump-turbine units. Units 1 and 2 have been in operation since 1995, and Units 3 and 4 began operating in 1999. The upper compensating basin for Chaira is the Belmeken Reservoir.
NEK invites sealed tenders from contractors for supply and installation of plant and equipment. Tendering is open to firms from all countries.
For Chaira, the subject of the current tender is all activities and components of the engineering service, such as the design, manufacture, delivery, dismantling, repair-restoration, installation, designer supervision, adjustment, testing and commissioning of the facilities. Specific equipment cited include the turbine, governor, plant control and monitoring system, relay protections, unit excitation system, vibration monitoring and analysis system, 19-kV switchgear for the generator/motor and nodal 19-kV switchgear, technical water supply pumps, electric energy metering systems, ventilation systems, and common auxiliary equipment and materials.
NEK received grant funds from the Kozloduy International Decommissioning Support Fund toward the cost of rehabilitating its Belmeken-Sestrimo-Chaira hydro complex and the Vacha-1 110-kV switchyard. Additionally, NEK will use its own funds to complete the work.
The Belmeken-Sestrimo-Chaira complex also includes the 375-MW Belmeken pumped storage project, 240-MW Sestrimo hydro plant, and 120-MW Momina Klissura hydro project.
In total, NEK owns 30 conventional hydro and pumped storage plant with a total installed capacity of 2,713 MW in generating mode and 937 MW in pumping mode.