Optimal Design of Pressure Relief Valves in Hydropower Stations

For some hydropower stations with longer pressurized pipelines, the by-pass pressure relief valves (PRVs) with an optimized coordinating control strategy are preferred to surge tanks for controlling transient pressures. Based on the method of characteristics, a simulation model of a hydro-mechanical system is built to connect the detailed flow characteristics of the PRV to a coordinating control strategy for the wicket gate closing law. This overall model must consider whether or not the PRV normally opens as well as the nature of both its opening and closing relations. Furthermore, the SMS formula for the maximum rising rate of unit’s rotational speed is discussed in detail and included in further analytical analysis. Based on this preferred empirical formula, for the maximum rising rate of unit’s rotational speed, the consistency and deviation between its analytical solutions and numerical solutions are further analyzed and illustrated. Specific system analysis also indicates that, with a sufficient flow capacity of the PRVs and an optimal coordinating control strategy for the units and PRVs, all the operational constraints including the maximum water hammer and maximum unit’s rotational speed can be satisfied.