Approach to sediment monitoring in Hydro Power Plant

Abstract

The presence of mineral sediments in water led to significant erosion damage to a power plant in the Chilean Andes. The plant is operated by Enel and is equipped with three vertical Francis power units, with approximately 25 MW each operating under a net head of around 120 m. The overall machine condition with reported significant damage on the turbine caused by erosion led to a modernization project with runner replacement and output and efficiency increase. In order to ensure a proper sediment measurement and quantification during the turbine operation, Voith developed, supplied and installed a sediment monitoring system in power unit #01. The monitoring system, developed using the OnCare.Health Hydro platform, applies optical sensors installed directly in the spiral case inlet section to measure the water turbidity. Other operational parameters are recorded, processed and stored together in the same database. Two optical sensors were installed in the spiral case inlet section and provide turbidity readings. The first one is positioned directly flush to the flow. The second one is located in a sampling pipe that collects water from four different points of the same cross section. An automatic water sampler installed in the sampling pipe collects water periodically, which is sent to a laboratory for particle analysis. The laboratory results allow an identification of important parameters such as sediments concentration, particle sizes and materials that are used for correlation with the indicated turbidities. The main data analysis shows that the power unit operated most of the time close to the rated condition. A comparison between turbidities indicated by both sensors shows an offset, probably associated to the particles distribution along the cross section. A system calibration process successfully correlated suspended sediment concentration and turbidity values to allow online indications of the sediment concentration. The system has been operating for almost two years in a close cooperation with the engineering teams of the plant owner and system provider. Main results and system findings for this application will be presented and discussed in this paper.