23 rd IAHR Symposium - Yokohama October 2006 1 (13) Feasibility of on-board measurements in a hydraulic turbine C. G. RODRIGUEZ Tech. Univ. of Catalonia, Spain cristian.rodriguez@mf.upc.edu E. EGUSQUIZA Tech. Univ. of Catalonia, Spain egusquiza@mf.upc.edu X. ESCALER Tech. Univ. of Catalonia, Spain escaler@mf.upc.edu Q. W. LIANG Tech. Univ. of Catalonia, Spain quanwei@mf.upc.edu Key words: Hydraulic turbomachinery, on-board measurements, vibration analysis. Abstract The vibration used for condition monitoring of pump-turbines is generally measured in the bearings. Nevertheless, the bearings have their own frequency response function which modifies the vibration from the turbine runner where the critical excitations are applied. Measure before the vibration pass trough the bearings emerges as a solution to avoid the signal contamination, and to achieve this purpose it is necessary to measure in the rotating shaft. Nevertheless, the use of telemetry and on-board measuring systems in rotating structures has not been widely used for monitoring. Nowadays this technology is affordable but it is not popular because the signals are difficult to interpret. In this paper the basic theory to interpret the rotating measurements is pointed out. After that, an analysis of an actual hydraulic turbine is carried out comparing vibrations measured on- board and in the bearings. Finally, these measurements are related with pressure measurements which correspond to the excitation acting over the runner. The on-board measurements show to be less contaminated than the traditional measurements and to be more related to the excitation in the turbine runner giving more and better information to achieve the condition monitoring. Introduction In pumped storage stations the critical failures are related with hydraulic forces acting over the impeller-runner (Ref 1, 2, 3, 4, 5 and 6). The most adequate technique to detect these forces is to measure the pressure near the perimeter of the impeller-runner. To measure there, it is necessary to drill the machine in the head cover or in the volute. This installation is a delicate and expensive work that most of the companies prefer to avoid. For that reason, hydropower companies prefer to measure vibrations because they do not intervene with the production and also are cheaper. Consequently, vibrations are the measurements used to detect the hydraulic forces acting over the runner. This vibration is usually measured in the radial