Mozgovuy A. Probabilistic assessment of reliability and safety of hydraulic structures of cascades of hydropower plants

In the presented work, a mathematical modeling of the strength and stability of hydraulic structures of the cascade of hydropower plants and their bases by probabilistic methods in the framework of the system reliability theory was performed. Despite the wide application of probabilistic methods for assessing the reliability of hydraulic structures, guidelines for assessing the reliability of complex technical systems, taking into account multifactorial influences, are not formulated. It is shown that modern literary sources overlook correlations between natural factors of influence, obviously inherent to hydropower plants, in particular. Based on the above, main objectives of the study were formulated. Distribution functions for the annual maximum earthquake magnitudes are selected. On the basis of the analysis of statistical data of temperature influences in hydropower schemes of the Dnipro Cascade, distribution functions for the annual lowest average monthly temperature and the annual maximum amplitude of the average monthly temperatures are selected. On the basis of the analysis of statistical data of annual maximum wind speeds in the geographical locations of hydropower plants of the Dnipro Cascade, distribution functions for the annual maximum wind speeds are selected. On the basis of analysis of statistical data, distribution functions for the annual maximum ice thickness in reservoirs of the Dnipro Cascade are selected. On the basis of processing statistical data of natural factors, correlations between the following random variables are investigated: between annual maximum flood flows, between annual maximum ice thickness, between annual maximum maximum average monthly temperatures, between annual maximum amplitudes of average monthly temperatures on the sites of hydropower schemes of the Dnipro Cascade. The obtained data testify to the close, and sometimes, practically functional dependence between random variables of natural factors. According to the probabilistic assessment of the reliability of hydraulic structures in hydropower schemes of the Dnipro Cascade of hydropower plants, in the framework of the parametric theory of reliability using a weak link principle, a block diagram of subsystems of the analytical generalized tree of failures and malfunctions, as well as a generalized tree of failures and malfunctions of the Dnipro Cascade of hydropower plants, is developed. An algorithm of probabilistic assessment of reliability and safety of hydraulic structures of the Dnipro Cascade of hydropower plants in the framework of the system reliability theory is developed. A design value of the risk of an accident on the Dnipro Cascade is obtained, which is equal to Pus = 0.00047 1/year. The results of the dissertation work are introduced into the practice of designing of hydraulic structures, as well as in the educational process.