Modelling, Simulation, and On-line Detection of Rotor Eccentricity in Hydropower Generators
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- Institutt for elkraftteknikk 
The generator is a critical component in the hydropower power plant, and detection of its fault conditions is important for safe and cost-effective operation. A new proposed method for detection of rotor interturn short circuits (ITSC), based on detecting harmonic sidebands produced around the main harmonic (the 50[Hz]) and its third harmonic (the 150[Hz]) when there is a fault on the generator, might be used for detection of eccentricity fault conditions on hydro generators . This master thesis investigated the ability of the rotor interturn short circuit detection method to detect eccentricity and differentiate between eccentricity and rotor interturn short circuit faults. The thesis also investigated the method s capability to detect rotor ITSC with static eccentricity. The method was investigated through simulations using the finite element simulation software Ansys Maxwell. The simulations has been made on a model based on technical drawings of a real generator, and three models with slight modifications in generator topology. The results of the simulation showed that the method is highly dependent on generator topology, and is unsuited for some generator topologies. For the cases it is suitable it can detect rotor ITSC with static eccentricity even at low levels of fault severity. Dynamic eccentricity can be detected as it entered critical levels. Mixed eccentricity can be detected, but some critical levels of the fault can go unnoticed by the method. The method is unsuited for detection of static eccentricity. There has also been found a way to differentiate between eccentricity and rotor interturn faults based on the amplitude of two of the harmonic sidebands.