Recently, the purely mechanical-hydraulic overspeed protection system for cylinder valves, jointly developed by DEM and DEA, was officially commissioned at the Bara Hydropower Station. This system enables the cylinder valve assembly to reliably close using purely mechanical-hydraulic means during unit overspeed, filling a technical gap in the industry and marking a world-first innovation.

The Bara Hydropower Station is located in Barkam City, Ngawa Tibetan and Qiang Autonomous Prefecture, Sichuan Province. It is the second cascade station in the planned 3-reservoir, 28-level development of the main stream of the Dadu River. The station has a total installed capacity of 746MW, comprising three 240MW hydro turbine-generator units and one 26MW ecological unit. The turbines for the three 240MW units are designed and supplied by DEM. Upon completion, the project will continuously optimize local power resource allocation while protecting downstream ecosystems, making a significant contribution to the comprehensive green transformation of economic and social development.

As the most critical equipment for preventing runaway speed, the cylinder valve requires redundant control systems and must be capable of linkage closure with a purely mechanical overspeed protection device. The purely mechanical-hydraulic overspeed protection system is a subsystem of the fully digital integrated hydraulic cylinder valve control system. In addition to standard cylinder valve control functions, it can achieve high-precision safe closure of the cylinder valve using purely mechanical-hydraulic drive even under complete power loss conditions.

In June 2024, DEM and DEA jointly launched development based on the existing fully digital integrated electro-hydraulic control system, successfully overcoming this technical challenge. The system completed factory acceptance in March this year and received unanimous recognition from the owner's experts. In May, on-site real-machine testing was completed, achieving synchronization accuracy of 0.46mm and a fastest closure time of 70 seconds—far exceeding design requirements. This commissioning marks the industry's first application of purely mechanical-hydraulic overspeed protection system technology.

The fully digital integrated electro-hydraulic control system is the third-generation control system independently developed by DEM and DEA. It integrates all electro-hydraulic control components within digital cylinders, transforming complex speed and position control tasks into easily managed digital pulse control. This not only improves response speed and control accuracy but also enhances synchronization performance while simplifying the control principle. Additionally, the system offers strong anti-interference capability and ease of commissioning and maintenance. The technology has been successfully applied in numerous large-scale hydropower stations, including Jinping-I, Xiluodu, Miaowei, Huangdeng, Yingliangbao, and Malda.