Calculation and Analysis of the No-Load Voltage Waveform of Large Tubular Hydro-Generators under Specific Damper Bar Damaged Failure

In this study, no-load voltage waveforms of tubular hydro-generators under a specific damper bar failure are analysed via a multi-slice moving electromagnetic field-circuit coupling model to derive a potentially simple criteria for the detection of this failure. Parameters that affect the no-load voltage waveform quality are considered, including the Total harmonic distortion(THD) and Telephone-influence factor (TIF). The influence of different structures such as the stator slot skew and the damper bar and pole shoe shift is investigated. The results show that the THD, the TIF and the no-load voltage waveform quality deteriorate as the number of damaged damper bars per pole increases, provided that the stator slot is not skewed. Furthermore, the influence of such failure on the no-load voltage waveform is revealed, which provides a new idea or possibility for indirect monitoring or diagnosis of such faults.