Novel discharge measurement system at the turbine intakes of Iron Gate 2 hydropower plant: a system description

Abstract

To quantify the hydraulic performance characteristics of hydraulic turbines several basic quantities need to be accurately determined. Discharge, or flow rate, is the most difficult quantity to measure as the measurement uncertainty is higher and more difficult to estimate in comparison to the power and head. Design of a discharge measurement system is governed by both the geometric and flow conditions at the measurement site, as well as by the physical properties of the fluid. Moreover, in adverse or non-standard flow conditions, special care must be taken to allow for the measurement system to capture the discharge data with acceptably low measurement uncertainty. In this paper, a general description of a novel discharge measurement system, designed and installed at the Iron Gate 2 hydropower plant, is provided. The system can be installed at the turbine intake, upstream of the trash rack, on one turbine at the time. Discharge value is acquired by employing a Velocity-Area aproach. Robust steel frame, carrying 15 novel 3D electromagnetic velocity probes, along with the 2 acoustic doppler velocimeters, is traversed along the cross sectional flow area allowing for accurate velocity field mapping. Position of the traversing frame is determined with two position transducers while two pressure transducers are used for the water level measurements. The measurement system was used at two turbines at the Iron Gate 2 HPP, capturing discharge with low measurement uncertainties.