Fault Analysis And Diagnosis Of Inter-turn Short Circuit Of Large Turbogenerator

Rotor inter-turn short-circuit fault is one of the common faults of the turbine generator,and early accurate detection is of great significance to the safe and stable operation of the power system.After the inter-turn short circuit occurs,the effective turns of the rotor windings are reduced,the magnetomotive force is reduced and the waveform is distorted,resulting in distortion of the air gap magnetic field,and thus generating operating parameters change.In order to meet the power supply requirement,the generator excitation system automatically adjusts,the excitation current is changed,and the fault characteristic quantity will change accordingly,which will affect the accuracy of the fault monitoring and diagnosis.The defects of detection methods will also have some impact on fault monitoring and diagnosis.Therefore,the accurate analysis of the fault feature quantity and the new detection method proposed are helpful to improve the accuracy of the monitoring and diagnosis of the rotor inter-turn short-circuit fault.This is of great significance to the normal operation of the generator.The main work of this paper is as follows.(1)Taking the QFSN300-2 turbo-generator as the research object,the model of generator based on field-circuit coupling was established by using Ansoft-Maxwell,Ansoft-Simplorer and Matlab-Simulink.The correctness of the model was verified.(2)The variation regularities of each fault feature were analyzed when the rotor short circuit is generated in the different excitation modes.Taking two kinds of typical excitation modes as constant excitation current and constant excitation voltage as examples,the basic characteristics of inter-turn short-circuit faults of rotor windings were calculated and analyzed from the view of magnetic field,basic electric quantity and electromagnetic torque.This provides a basis for the study of generator rotor inter-turn short-circuit fault under the automatic excitation regulation system.(3)A new method of detecting coil is proposed: U-type detecting coil method.The simulation model of the 300 MW turbine generator is utilized,and the U-shaped detection coil was installed at the stator core of the generator.Under the no-load and rated load conditions,the simulation of rotor inter-turn short-circuit fault of different degree was done respectively,and the law of magnetic flux and induced voltage flowing through U-shaped detection coil was obtained.The method has high practicability and can be used as a diagnosis method for rotor inter-turn short circuit faults.