Efficiency measurements at Vessingfoss power station

Abstract

A measurement of the hydraulic turbine efficiency at the Vessingfoss hydro power station by the thermodynamic method has been attempted, but has not given the desired results. Two problems have been encountered. The high pressure side temperature measurements show an abnormal scatter resulting in standard deviations of sy=0.05ºC. The reason for the scatter may be temperature layers in the reservoir lake Nesjø. This theory has been investigated, but needs further work. The other problem has been the mechanical strength of the low pressure side collector probes. Two different collectors have been tried, and both have broken down. The second attempt was made with a collector design based on wire rope, which failed because the turnbuckles were under-dimensioned. With proper dimensions, this solution is interesting in the future, as it was easy to install and may contribute to lose collector weight. The relative turbine efficiency has been calculated based on pressures and levels measured during the thermodynamic test. An uncertainty analysis of the result has been carried out. The head loss has been calculated based on technical drawings of the penstock and loss coefficients from the literature.