Hydroelectric power plant of Chaira (Chaira PSHPP) was built in the Rila Mountains, about 100 kilometers southeast of the Bulgarian capital, Sofia. Chaira has a generating capacity of 864 megawatts (1,159,000 HP) and a pumping capacity of 788 megawatts (1,057,000 HP). The plant is equipped with four reversible Francis-type pump-turbines, each with a power of 216 megawatts (290,000 HP) in generating mode and 197 megawatts (264,000 HP) in pumping mode. Units 1 and 2 have been in operation since 1995, and during that time, Chaira was the largest pumped-storage power plant in southeastern Europe, with the highest single-stage pump-turbine drop in the world (690 meters in generating mode and 701 meters in pumping mode). Units 3 and 4 were commissioned in 1999. The pump-turbines and generators were supplied by Toshiba, with three of them produced in Bulgaria under Japanese supervision. The upper reservoir for Chaira is created by the Belmeken dam, which connects to the pumped-storage power plant via two 4.2-meter diameter penstocks and two 4.4-meter diameter pipelines, reducing to 4.2 meters. Water flowing from the Belmeken reservoir supplies the Sestrimo hydroelectric power plant (Wikipedia).

This time, the scope differs from the other projects of the year: milling of the spillway edge guides.

For this purpose, a special machine tool has been designed and built.