On the Shaft Voltage to Detect Faults in Wind Generators

The aim of this paper is to present the first insights coming from an experimental research focused on the investigation of the shaft voltage measurement and analysis as a diagnostic tool for wind generators. Since in wind farms the rotating electrical machine is usually a doubly-fed induction generator or a permanent magnet synchronous generator, it is connected to the grid through an electronic converter, which produces a common mode voltage and, consequently, a shaft voltage. In this paper, the correlation between these two signals will be shown in detail, through the analysis of experimental measurements in laboratory, which demonstrate the strong diagnostic content of the shaft voltage signal. The harmonic analysis of this signal, both at low and high frequencies, is proposed as a new index for the preventive maintenance in wind power generation.