Study On Electromagnetic Characteristic Analysis And Fault Diagnosis Method Of Generator Under Rotor Winding Inter-turn Short Circuit

Rotor winding inter-turn short circuit, which is one of the commonest forms of turbo-generator failure, has been plaguing power producers with respect to production safety and economy. This fault will change the state of the electromagnetic field in generator, cause the distortion of air-gap magnetic field. This thesis presents an investigation of the behavior of a turbo-generator in case of rotor winding inter-turn short circuit, focusing on the affection to the steady-state electromagnetic field and the electromagnetic torque. The main work of this thesis are as follows.(1)The thesis provides some insight into the influence of the rotor winding inter-turn short circuit level and position upon air-gap magnetic field under rated running state of generator. With a QFSN-300-2-20 B turbo-generator as the research object, the finite element simulation model of the generator rotor winding short circuit was established,and the variation of tangential and radial flux density of air-gap magnetic field was analyzed.(2)The relationship between electromagnetic torque and the actual degree of short circuit when rotor winding inter-turn short circuit fault under rated conditions was analyzed. Thus, a fault diagnosis method was proposed. By the contrast analysis of the electromagnetic torque of the generator under the assumption of no short circuit rotor winding and actual short-circuit fault, which is calculated by using the finite element method, if the deviation is greater than the set threshold, the situation will explain the presence of generator rotor winding short circuit faults. Moreover, this method has been validated through a case of fault.(3)By means of VB and ANSYS APDL language, based on the proposed rotor winding inter-turn short circuit diagnostic method, which is a electromagnetic torque comparison, a diagnosis system for the inter-turn short circuit of the rotor winding was developed. And this system implements a visual diagnosis of the inter-turn short circuit of the rotor winding of turbo-generator with high accuracy. Also, the reliability and practicability of the system has been verified by the example of QFSN-300-2-20 B turbo-generator.