Abstract
This paper presents results from an experiment performed to obtain the dynamic characteristics of a reversible pump-turbine model. The characteristics were measured in an open loop system where the turbine initially was run on low rotational speed before the generator was disconnected allowing the turbine to go towards runaway. The measurements show that the turbine experience damped oscillations in pressure, speed and flow rate around runaway corresponding with presented stability criterion in published literature. Results from the experiment is reproduced by means of transient simulations. A one dimensional analytical turbine model for representation of the pump-turbine is used in the calculations. The simulations show that it is possible to reproduce the physics in the measurement by using a simple analytical model for the pump-turbine as long as the inertia of the water masses in the turbine are modeled correctly.
Highlights
For new or upgraded high head power plants, transient analysis is often an important part of the scope
The measured dynamic characteristics showed behavior according to the stability criterion predicted by Martin
The same result was obtained for a high head Francis turbine model by Nielsen in 1990 and explained by means of inertia in the water masses inside the turbine
Summary
For new or upgraded high head power plants, transient analysis is often an important part of the scope. This analysis gives information regarding maximum pressure in the penstock, minimum pressure in the draft tube and maximum overspeed during load rejection. The system’s response to ramping of load, transient response of the governor and stability can be investigated with appropriate software. Today’s software covers most of the needs regarding analysis of the dynamic system, but lack of information regarding the turbine in an early stage of a project will necessitate an analytical approach with respect to turbine modeling. Nielsen [1,2] presented a simple analytical model for high head Francis turbines in 1991 and an improved version suitable for reversible pump-turbines in 2010. The model requires a minimum of input data and has proven good accuracy with measured data
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