Flödesmätning i vattenkraftverk
Studie av alternativa mätmetoder
Flow measurement is one of the greatest challenges in order to calculate efficiency in hydropower. Most hydropower plants in Sweden use differential pressure methods for flow measurement. These methods are dependent on constant conditions in the waterways. A change in these conditions, like turbine improvements, prevents differential pressure methods to verify efficiency improvements. Since efficiency improvements can?t be verified by one measurement system, another method, which isn?t affected by changing conditions, can be used. This other method can calibrate or support the primary flow measurement system.This study investigates the possibility of designing such a method. The potential of different flow measurement methods have been estimated through literature study. Laboratory experiments were conducted on two measurement systems, designed from two differential pressure methods. From the result from these experiments, a system for field measurement was designed from the lab prototype and tests were made in a hydropower plant. The method is unaffected by improvements in the waterways since it?s placed on the intake.The field measurements generated test data, from which a relative flow measurement model was made. The model approximated the higher flows with a relative error between 0,5 and 5,0 %. However, the model has weaknesses that partly depend on bad quality in measurement data. More tests are required to verify the method. The method is applicable in most hydropower plants, simple and relatively easy to install.