Improved prediction of Pump Turbine Dynamic Behavior using a Thoma number dependent Hill Chart and Site Measurements

Abstract

Water hammer phenomena are important issues for the design and the operation of hydro power plants. Especially, if several reversible pump-turbines are coupled hydraulically there may be strong unit interactions. The precise prediction of all relevant transients is challenging. Regarding a recent pump-storage project, dynamic measurements motivate an improved turbine modeling approach making use of a Thoma number dependency. The proposed method is validated for several transient scenarios and turns out to improve correlation between measurement and simulation results significantly. Starting from simple scenarios, this allows better prediction of more complex transients. By applying a fully automated simulation procedure broad operating ranges of the highly nonlinear system can be covered providing a consistent insight into the plant dynamics. This finally allows the optimization of the closing strategy and hence the overall power plant performance.

Hydraulic Oscillation and Instability of A Hydraulic System with Two Different Pump-Turbines in Turbine Operation

“…, where, τ is the dimensionless valve position; C d A G is the coefficient of the discharge times area of valve opening; and τ' is a small perturbation of the guide vane position with amplitude, T V , and angular frequency, ω, for time, t. "Re" represents the real part of the complex value within parentheses and subscript "0" stands for the initial steady condition. Equations (12) and (13) are represented in the matrix form as…”

“…In addition, the hydraulic system in Figure 2 is modified to the equivalent system consisting of eight different pipes. The various pipes in series (1-6), (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), (17,19,21), (18,20,22), (23,25,27,29,31), (24,26,28,30,32), (33,34), and (35-38) of the original system shown in Figure 2 were substituted by their respective single equivalent pipes [30]. The sensitivity analysis was carried out with the equivalent system for OS 2 and OS 3 .…”

“…Using software SIMSEN, Nicolet et al [12] determined the certain time period for interchange between the rigid and elastic water column oscillation phenomenon. Marderla et al [13] investigated the influence of the Thoma number on the turbine hill chart simulating the whole hydraulic system and concluded that the higher value of the Thoma number rendered the increment in the S-shaped characteristics. Yamaguchi and Hayami [14], Hayami et al [15], and Chen et al [16] performed many experiments to visualize the internal flows of the pump-turbine model during S-shaped characteristics, with a miniature video camera fitted at the main shaft of the runner.…”