Analysis And Protection Of The Rotary Armature Winding Fault And The Rotary Diode Fault Of Multi-phase Annular Brushless Exciter In Nuclear Power Plant

The multi-phase annular brushless exciter is widely used in large-capacity nuclear power generation units.The realization of reliable protection for the exciter internal faults is of great significance for the safe operation of nuclear power generation units.Because the multi-phase annular brushless exciter is adopted with rotary armature structure,the faults of rotary armature windings and rectifier diodes cannot be directly monitored.However,it is an effective way to realize the fault monitoring according to the fault characteristics reflected in the stator field winding.In the thesis,for the faults of the rotary armature windings and rectifier diodes of the exciter,a series of research work included simulation modeling,dynamic experiment,theoretical analysis and protection scheme design have been carried out.Accurate simulation model is the basis of studying fault characteristics and protection method.In this paper,based on the multi-loop method and the network correlation transformation matrix,the mathematical model of the multi-phase annular brushless exciter with the rotary armature winding fault and the rotary diode fault is established,and the corresponding simulation program is compiled.Based on the multi-loop method,the simulation of the multi-phase annular brushless exciter system in the normal operation,the rotary armature winding short-circuit fault and the rotary diode open-circuit fault can be carried out respectively.In order to verify the proposed model,the simulation and experiment of normal operation,armature winding short-circuit fault and rectifier diode open-circuit fault are carried out on an 11-phase annular exciter prototype.By comparing simulation waveforms with experiment waveforms,the correctness of the model is verified.Furthermore,by comparing harmonic components of simulation waveforms with that of experiment waveforms,the simulation accuracy of the model is also verified.In this thesis,the harmonic characteristics and its mechanism of the field current under normal operation,armature winding short-circuit fault and rectifier diode open-circuit fault are analyzed in detail.The model verified by experiment is used to simulate different operation conditions of the actual exciters,which verifies the correctness of the theoretical analysis.Both the simulation results and theoretical analysis show that the exciter field current has different harmonic characteristics under different operation conditions.Finally,according to the harmonic characteristics of exciter field current obtained from simulation calculation,experiment research and theoretical analysis,the protection scheme and its setting method of multi-phase annular brushless exciter rotary armature winding and diode fault are proposed:Based on the ratio of the 2^nd to the 4^th harmonic,the the rotary armature winding fault and the rotary diode fault can be distinguished;and based on the ratio of the odd to the even harmonic,the one-diode,one-phase and two-phase open fault can be judged.The proposed protection method will not make the field exciter be retrofitted,which is practical.The research in the thesis lays a foundation for the reliable and sensitive protection of the internal faults of the nuclear multi-phase annular brushless exciter,which is of great significance for the safe operation of the large-capacity generation sets.