Simulation And Protection Of Internal Short Circuit Faults For Powerformer

Powerformer is a new kind of high-voltage generator, which can be connected to power network directly. It omits the impact voltage protectors, the generator breaker, bus bars, and the step-up transformer. The power plants equipped with Powerformers have advantages of low cost, high efficiency and low maintenance etc as a whole.Powerformer appeared at the end of last century, although there are some Powerformers operation, the analysis on them still at starting stage. So studying on operation laws and features about Powerformer has theoretical significance and engineering value. The internal short circuit faults are serious problem during generator operation. In order to discuss the analysis methods, change laws about fault currents and protection schemes to internal short circuit faults, this dissertation researches the internal short circuit faults in Powerformer.Firstly, the transient process of Powerformer during internal faults in stator studied deeply in the dissertation. Then, mathematical models of Powerformer, which can analyze internal faults, are proposed on the base of a direct phase representation. And simulate models are built found on Matlab/Simulink. The models not only simulate faults when the generator neutral point is either high resistance ground or erc-suppression coil ground, but also perform when faults occur at different locations along the winding.Secondly, simulations on different internal faults, including single phase-to-ground faults, two phase-to-ground faults, phase-to-phase faults based on a 130 kW/ 5 kV Powerformer are done. The change laws of stator currents, fault currents and grounding currents are obtained.Lastly, to protect Powerformer's internal faults, the relay protection schemes are designed, and the protection parameters are analyzed and calculated in detail. The study provides an academic flat in some degree for choosing and designing the protection schemes for Powerformer in the future.