Abstract: In engineering practice, bulb tubular turbine units in hydropower station is prone to overspeed and low-frequency magnetic field suppression during load shedding due to small head, large flow, and small rotational inertia. Taking the hydropower units of Vitebsk hydropower station in Belarus as a case study, we expound the structure and basic principle of the speed governing system containing digital cartridge valve. On the basis of on-site test data of the speed governing system, we analyzed the strategies and advantages of digital cartridge valve in speed governing system. By improving the collaborative relationship between guide vane and blade, and adjusting the real-time regulating control of unit, the abovementioned problems are solved. The result manifests that digital cartridge valve is highly reliable for the speed regulating system of hydropower turbine, with the control accuracy and stability meeting standard requirements, hence is of good engineering application value.

Key words: speed governing system, digital cartridge valve, high-speed switching valve, bulb tubular turbine unit, low-frequency magnetic field suppression, load shedding, Vitebsk hydropower station