LIFETIME EVALUATION OF THE MECHANICAL ELEMENTS FOR A RUN-OF-RIVER HYDROELECTRIC POWER PLANT

A complex energy grid is the ground base of the development of any modern society and any competitive economy. Its safety in operation assures the continuity in energy supply for all economic and social sectors. The Romanian national grid has faced changes in the development of the renewable energy sources, while having a wide range of other power generation capacities in hydro, thermal and nuclear. When an electricity grid is facing strong fluctuation in the demand curve, the need of balancing the grid frequency and voltage becomes a challenging task for dispatchers and producers, especially when an important capacity of the grid is installed in wind farms and photovoltaic plants. This paper presents the results of simulations of the behavior of a Kaplan turbine within a hydroelectric power plant (HPP) which is providing system services to the grid. The main system services provided by HPP is frequency and voltage regulation. The frequency adjustment is done by all units within the grid system in order to keep the overall frequency of the grid within admissible limits in order to balance the supply and demand power. However, due to the specificity of the primary source, the HPPs are the most used in this type of services because they have the capacity to start-up, shutdown and adjust the produced energy very quickly by modifying the discharge to the turbines to meet the requirements of the National Dispatcher. The increase and reduce of the generated power during short time intervals might generate an impact on the equipment, the embedded parts and construction elements especially when irregular phenomenon appears (high bearings vibrations and temperatures). For the purpose of the study presented in this paper a run-of-river HPP equipped with a Kaplan turbine was selected. In this regime, the unit will generate power according to the grid needs, with strong variations in generated power from 30% to 100% of the nominal capacity, variations that occur on hourly basis. This regime is not a normal operation regime for a run-of-river HPP which should operate constantly at the base zone of the power demand curve. Numerical simulation and finite element method analysis software was used to determine the lifetime based on fatigue analysis.