Vibration Monitoring of Hydropower Systems

Abstract

Excessive vibration in hydropower systems is often an indication of a failure of equipment that can lead to fatigue issues or complete shutdown of a system. Localizing the source of the vibration and identifying the cause is crucial to evaluating the structural integrity and ensuring its continued operation. At a hydropower plant in Arkansas, substantial vibration was being generated within one of the hydropower units when brought offline, when no flow should be occurring through the unit. On site personnel suspected that the vibrations were coming from the wicket gates, whose opening and closing controlled the flow of water through the unit. Observations lead to the belief that leakage-flow induced vibrations were being generated by a permanent gap between adjacent gates in the closed state. Within the hydropower unit, the wicket gates are fully submerged underwater, and visual inspection of the body of each gate requires the unit to be completely drained of water. Thus, a short-term monitoring program was designed to use accelerometers to measure the magnitude of vibration coming from the wicket gates using only the gate stems accessible along the outer ring of the unit. The source of the vibration was localized by investigating the energy of vibration produced from each wicket gate and where the vibration initiated as the gates transitioned from open to closed. The results of this study were verified during a later dewatering of the unit where gaps between adjacent gate pairs were measured. The results of this effort provide a method for localizing excessive vibration in hydropower units in need of maintenance.