A New on-Line Diagnosis Method for Inter-Turn Short Circuit of Hydro-Generator Rotor Windings Using a Flexible Equivalent Coil

The inter-turn short-circuit (ITSC) fault of hydro-generator rotor windings will lead to the asymmetry of the main magnetic field, which may cause strong vibration and result in a shutdown accident. Inspired by the existence of large number of cross-core screws in hydro-generators, two screws with fractional or integral multiples of generator polar distance are selected and used to form an equivalent coil, so as to construct a semi-intrusive fault detection sensor layout scheme. The theoretical analysis of our method was conducted and real time ITSC fault detection according to specific harmonics in the induced voltage in the equivalent coil was proved to be feasible. Finally, through the finite element simulation and fault simulation test, it is shown that when the ITSC of hydro-generator rotor winding occurs, the fractional harmonics appear in the induced voltage of the equivalent coil, which proves the effectivity of our method in determining the ITSC fault. The signal acquisition by using our method is convenient. Besides, the coil pitch is flexible, which is beneficial for both signal acquisition and feature highlighting.