Identification of sensitive feature in the stray magnetic field to detect rotor short-circuit fault in synchronous generators

This paper presents an application of the external magnetic field measured in the vicinity of a synchronous generator in a hydroelectric powerplant for the detection of a rotor short circuit fault. The measurement of the external magnetic field was performed using a flux sensor and the analysis of the signal is done in a quantitative and qualitative way by considering the spectral evolution of the signal but also its temporal variation. The presented results are obtained analyzing several operating conditions of a 55 MW generator in healthy and fault case. We notice the interest of using the reduced values in percentage to better compare the different state of the machines. A vibration study is also presented at the end of the paper to complete the analysis.