A new approach to using the classic pressure-time method of discharge measurements

Discharge measurement using the pressure-time (Gibson) method typically involves mounting measurement instrumentation on the outside of the penstock. In the case of a hydropower plant where the penstock is built over concrete, an innovative approach is necessary in order to install instrumentation inside the penstock. Such instrumentation has been implemented for the purpose of efficiency tests of the upgraded small Kaplan turbine. The pressure-time method, in its classic version, requires sending pressure signals from both penstock cross-sections to the differential pressure transducer by means of connecting tubes. This raises the question on the influence exerted by dynamic properties of the connecting pipes/transducer system on the discharge measurement results. Calculations carried out using previously developed method enable authors to demenstrate that the connecting pipes/transducer system had exerted a negligible influence on the discharge measurement results.