Detection Method Of Inter-turn Short Circuit And Eccentricity Fault In Rotor Winding Of Turbine Generator

In view of the common synchronous generator fault of rotor winding turn to turn short circuit and rotor eccentricity fault,the traditional fault diagnosis method is not sensitive and reliable.In particular,the on-line detection and location of rotor winding turn to turn short circuit is an important direction in the field of turbo generator fault diagnosis,which is also full of difficulties and challenges.In this paper,the electromagnetic characteristics of generator caused by rotor winding turn to turn short circuit and rotor eccentricity fault are studied.The main work is as follows:(1)The characteristics of the main magnetic field after the dynamic eccentricity,static eccentricity and turn to turn short circuit are analyzed.Based on the U-shaped detection coil method,a fault detection method of half speed turbo generator based on the double coil method is designed.Compared with dynamic eccentricity faults,the characteristics of the variations in the main magnetic field after a turn-to-turn short circuit in rotor windings were analyzed and the unique characteristics were extracted.We propose that the degree of a turn-to-turn short circuit can be judged by the difference in the induction voltage of the double U-shaped detection coils mounted on the stator core.Here,the faulty slot position was determined by the local convex point formed by the difference in the induced voltage.Numerical simulation was used here to determine the induced voltage characteristics in the double U-shaped coils caused by the turn-to-turn short circuit fault combined with dynamic eccentricity fault.Finally,we demonstrate the positive anti-interference performance associated with this fault detection method.(2)The characteristic harmonics of the main magnetic field after turn to turn short circuit of rotor winding and eccentricity fault are analyzed,combinin g with the calculation method of electromotive force of AC windings,the expression of 1/2harmonic electromotive force under a pair of poles is obtained under the condition that the 1/2 harmonic magnetic field generated by the fault is regarded as the mai n magnetic field and the stator winding is regarded as the ultra-short distance winding,the functional relationship between harmonic EMF and harmonic magnetic field is established.The expression of electromotive force in series of bipolar windings is further deduced.The waveform characteristics of parallel branch circulating current and the correlation between frequency characteristics and short circuit level and rotor eccentricity level are studied by numerical simulation,which provides theore.(3)Shaft voltage is an electrical phenomenon produced during the operation of synchronous generator,which is easy to cause electric corrosion of bearing bush,and can also be used to reflect the internal fault of generator.According to the principle of flux conservation,a method of calculating the shaft voltage in the process of finite element simulation is proposed,which overcomes the disadvantage that the fault can not be set flexibly in the fault simulation experiment.The characteristics of shaft voltage of rotor static eccentricity and rotor winding turn to turn short circuit are extracted,and the relationship between the harmonic frequency,harmonic content of shaft voltage and fault type and fault degree is obtained.