Measurement of loads acting on a hydropower unit during stationary and transient operations

Abstract

Load measurements on hydropower turbines and generators are usually expensive and troublesome due to the need of sensor installation on the rotating parts. Often a longer stop of the unit is required when the sensors are to be installed or removed from the turbine in the waterway, which results in production disturbances.This article presents a methodology and results for estimation of loads acting on turbines and generators during operation without installation of sensors on the turbine or in the generator. The measured quantities are shaft displacement in the bearings and the bending moment on the shaft between the turbine guide bearing and the lower generator guide bearing.To enable calculation of the loads acting on the turbine and the generator, it is necessary to have as many measurement points as the number of unknown loads acting on the shaft train. By using the displacement in the three radial bearings, six of the eight unknown forces can be determined. The remaining two unknown loads can be calculated by measuring the bending moment in the shaft connecting the generator to the turbine. In journal bearings the stiffness is a non-linear function of eccentricity, which means that the obtained stiffness function must be integrated to achieve the force as a function of the shaft eccentricity.By applying the measured time history of displacement and moment on the numerical model, the time history for the unknown loads can be solved. The time history of the external loads is then converted into load spectra.

Keywords

• Vertical rotor
• Numerical Analysis
• Bearing Stiffness
• Measurement
• Rotor Load