Signature Investigation of Typical Faults on Francis Turbines

Abstract

Hydropower is facing new operational strategies as the increasingly competitive power market demands for higher flexibility. Consequently, turbines are forced to handle tougher operation and are prone to more frequent degradation. By implementing a real-time monitoring system, a better understanding of the behavior of components may contribute to detect faults at an earlier stage, reducing potential downtime. This paper will present the work done in the preliminary work of the author's master thesis. The focus has been to characterize the normal behaviour of a Francis turbine through amplitude and frequency analysis. Steady-state measurements of pressure pulsations have been conducted on the Francis test-rig at the Waterpower laboratory at NTNU. Different hydraulic phenomena and respective frequencies were identified. In addition, the results revealed several unexpected frequencies and suspicious observations, and potential sources of these are discussed. Possible fault detection schemes based on peak-peak and frequency analysis are suggested. Alarm should be raised in case of mismatches in sensor relations, magnitude variations or if new harmonics or frequencies appears.