Analysis of transient processes for various laws of the guide vanes closing in Francis turbines with synchronous pressure regulating valves

Abstract

Safe and reliable exploitation of hydropower plants implies a due study of their behavior in different operating conditions, and the analysis of transient processes is necessary already at the design stage. Contemporary analyses of transient processes in hydropower plants involve complex and detailed numerical simulations of all normal, special and emergency operating regimes that can occur in exploitation. In order to protect these plants, it is necessary, among other things, to consider non-stationary phenomena in cases of various laws of closing the turbine guide vanes. In addition, one of the ways to protect hydropower plants with long derivative penstocks is the application of synchronous pressure regulating valves (SPRVs). SPRVs enable relatively fast closing of the turbine, while at the same time efficiently relieving the pipeline from increased pressure variations. SPRVs are mostly installed directly at turbine spiral case, and their opening law is often complementary to the closing law of guide vanes. Parameters of interest for proper adoption of the maneuvering laws of guide vanes and SPRVs comprise head envelopes along the penstock route, spiral case transient pressure and turbine transient over-speed. In this paper, the analyses of the previously mentioned water-hammer parameters were carried out for various multi-speed linear closing laws of Francis turbine guide vanes equipped with a SPRV.