The Influence of Using the Diversion Tunnel on Hydraulic Transient of Hydropower Plants

Reconstructing the diversion tunnel as a permanent construction is not new in large underground hydropower plants' design, however most of them are taken as spillway tunnels or tailrace tunnels. A new design method of using diversion tunnel was proposed for further utilization. This paper analyzed the influence of using diversion tunnel on hydraulic transient of hydropower plants, including shaft surging, water hammer and dynamic properties of the governing system of the turbine. Calculation results verified the assumption that using diversion tunnel could reduce chamber diameter of surge shaft. The results provide reference to future design for underground hydropower plants.