Study On Inter-turn Short-circuit Fault Detection Of Turbo-generator Rotor

The safe running of electrical equipment is key to power system. Generator is more important in the power system as the part of generating power. Especially China has been on the step of huge power network and huge generators. The capacity of generator augments continually. So the fault detection of generator is a necessary problem to solve. The turbo-generator is a kind of synchronous electrical machine rotating at high speed. When it operates, the rotor is always under the great suppression of centrifugal force. So the rotor windings often happen inter-turn shorted-circuit fault and grounding fault. The light inter-turn shorted-circuit fault hasn't important influence to generator, but If more seriously, which can lead to the vibration of generators, the magnetization of shaft, and harm the generator to stop working. So it is necessary to monitor the states of rotor windings of turbo-generator. Thus it can improve the security level of power system. In this paper the inter-turn shorted-circuit fault detection method of turbo-generator rotor windings is studied.At present there are many methods to detect the inter-turn shorted-circuit fault of turbo-generator rotor windings. The air-gap detection coil monitoring method is effective and used widely. In the application of differential detection coil method, the signal wave is directly studied on the screen. Actually if there is light fault, the change of wave is not obvious. Aiming at this, the wavelet transformation method ispresented in this paper, which can deeply decompose the signal induced in detection coil, and check the fault information truly and timely.In this paper the inter-turn shorted-circuit 1 fault occurred in rotor windings is studied. The inter-turn shorted-circuit fault can make air gap magnetic field vary, and let the peak and the average wane. The slight fault doesn't affect the power system, but through long period, the fault will develop into the grounding fault. One-point short may not cause much trouble except affecting the rotor's using periods of time. Two-point to earth fault may cause strong short currents which can lead to serious accident.Secondly, the paper amply analyzes the air magnetic field distributing. On well-balanced situation, the wave of air magnetic field is considered to approximate ladder form. On fault situation, the fault equals to the effect of canceling magnetism, which cause the induced potential distort. The method of air-gap coil is based on the mechanism to detect fault.Thirdly, wavelet analysis is a good measure to process signal during fault diagnosis. This paper introduces the wavelet analysis theory. Finally, the wavelet analysis toolbar is used to emulate the simulating signals, which validates the correctness of method. The result shows that the method of wavelet analysis combining air-gap detection coil can detect the inter-turn shorted-circuit fault.