Uncertainty assessment of flow measurements at Iron Gate 2

Abstract

To allow for the reliable hydraulic efficiency estimation of the tubular turbines before and after their revitalization at the Hydro Power Plant (HPP) Iron Gate 2, a novel flow measurement system was designed and tested on two turbines. In this paper the details of used approach for the assessment of the flow measurement uncertainty are presented. The presented methodology is tailored for specific application of the Velocity – Area flow measurements at HPP, based on the utilization of electro-magnetic velocity meters (EMVM), instead of traditional propeller current meters. Although the procedure for the assessment of the flow measurement uncertainty in similar cases of low-head plants and short intakes can be found in the literature, the adverse flow conditions, novel EMVM sensors and the specific operating modes have instigated a need for modifications and improvements of the procedure. Assuming analogy between the current meters and EM meters, the IEC 60041 and ISO 3354 procedure for flow rate measurement uncertainty assessment was used as a template, with implemented moderate changes accounting for the features of the applied measurement. Selected flow measurements from the 2020. campaign are analyzed, with an emphasis on the variation of the magnitudes of the measurement uncertainty components.