Critical stable sectional area of downstream surge tank of hydropower plant with sloping ceiling tailrace tunnel

This paper investigates the critical stable sectional area (CSSA) of downstream surge tank (DST) hydropower plant with sloping ceiling tailrace tunnel (SCTT). Firstly, two types nonlinear mathematical model SCTT during transient process are established. Then, criterion operation stability is obtained based on theory. Formulae for CSSAs DST under derived. Finally, similarities, differences, and relationships different clarified. The effect mechanisms assumption steady power output hydro-turbine CSSA revealed. recommended use conditions explained. results indicate that, hydro-turbine, formula analytical has a simple expression. Under complete model, not complicated former suggested to be given priority because good precision concise can improve decrease DST.