Generator Faults Cross-feature Analysis And Mechanical-electrical Joint Diagnosis Study

Generators mechanical and electrical faults influence each other. Traditional fault diagnosing methods don't pay much attention to the cross-feature.The sensitivity and reliability of diagnostic is not high. This article deeply studies generator vibration characteristics caused by electrical failure and electrical characteristics due to mechanical failure (ie, the cross-fault characteristics), establishes the method to diagnose generator faults by cross-information.The main work of this paper is as follows.(1)Put forward the method to detect the degree of generator static eccentricity fault based on shaft voltage. Air gap permeance method is adopted to analyze generator air-gap magnetic field characteristics under static eccentric state, verifies that the distorted flux can induce voltage at both ends of generator shaft. Shaft voltage is in proportion to the degree of generator static eccentricity, so the shaft voltage characteristic components can characterize the degree of generator static eccentricity fault.(2)The influence research of generator rotor windings inter-turn short-circuit electrical fault on the unit vibration characteristics. By Fourier Analysis Method, generator excitation magnetic potential mathematical expression is got, the variation rule of the unbalanced electromagnetic force with excitation current and generator state is studied after rotor windings inter-turn short-circuit. Aiming at the practical problem that the diagnosing reliability of rotor windings inter-turn short-circuit through the fundamental frequency component amplitude of rotor vibration signal is not high, the law of rotor force and vibration is studied under mechanical and electrical compound faults, the method to detect rotor windings inter-turn short-circuit fault is proposed, which is based on the rotor basic frequency vibration amplitude and angle change. To rule out the interference of the mechanical faults such as mass balance on the diagnosis of rotor windings inter-turn short circuit fault, stator core shell vibration rule under unbalanced electromagnetic force is studied, theoretical analysis and experimental confirm that we can effectively diagnose rotor windings inter-turn short circuit fault through the stator core vibration.(3)Put forward the method of detecting rotor windings inter-turn short circuit fault with the aid of stator cogging effect. The stator cogging effect is usually ignored when we calculate generator magnetic field by air gap permeance method, which lead to the generator fault information missing. This paper considers the stator cogging effect when establishing generator air-gap permeance model, theoretical analysis and experimental results confirm that when rotor windings inter-turn short circuit happens, the characteristic harmonic corresponding to alveolar numbers appears in shaft voltage, which can reflect rotor windings inter-turn short circuit fault.(4)Put forward to detect the rotor windings inter-turn short circuit fault with the aid of static eccentricity fault. This paper consider the inherent generator static eccentricity fault, generator magnetic field model is established adopting air gap permeance method after the rotor windings inter-turn short circuit fault, the theoretical analysis and experimental results show that the fault feature components appear after rotor windings inter-turn short circuit fault, which can effectively show the rotor windings inter-turn short circuit fault.