Selection and Optimization of Sensors for Monitoring of Francis Turbines

Abstract

With the current demand of flexibility to hydraulic turbines, these are working under off-design conditions more than ever. Under these conditions different complex hydraulic phenomena appear, especially in Francis turbines, affecting the machine stability as well as reducing the useful life of its components. Hence, it is desirable to detect in real-time these hydraulic phenomena to assess the operation of the machine. In addition, the position and type of sensor to detect these phenomena is a key point for the monitoring of Francis units. In this paper, a large medium-head Francis turbine was instrumented with several sensors such as accelerometers, proximity probes, strain gauges, pressure sensors and a microphone. Results obtained with the different sensors in different locations are compared to know which hydraulic phenomenon is detected with every sensor. Furthermore, different signal analysis techniques are also compared. With this information, monitoring systems can be optimized with the most convenient sensors, locations and signal analysis techniques, reducing its difficulty to install and economic cost.