Fault Simulation And Monitoring Scheme Of Nuclear Multiphase Brushless Exciter And Rotary Rotating Diode

Brushless excitation cancels carbon brush and slip ring,and has high reliability and low maintenance workload.It has become the pref-erred excitation mode for large capacity nuclear power generating units.However,the armature winding and rotating rectifier of the brushless exciter have been in high speed rotation,and the rotating diode is very easy to fail.It is very difficult to protect and monitor it.The aim of this thesis is to realize the on-line monitoring of the fault of the rotating rectifier system of the brushless exciter by using the electrical quantity in the operation,and to find the early fault state of the rotating rectifier,so as to avoid the serious accident caused by the long failure operation.In order to break through the research bottleneck of the exciter electrical quantity that can not be accurately calculated in the past,this paper uses the finite element method to analyze the internal electromagnetic field of the brushless exciter,and establishes the field path coupling model of the brushless exciter and the rotating rectifying system on the Ansys/Maxwell simulation platform.The model is established according to the actual structure and actual size of the exciter.It can simulate the normal and fault running state of the rotating rectifier,and obtain the electrical quantities(such as voltage,current,magnetic chain,etc.)in various operating states.In this paper,the 39 phase brushless exciter of Hongyan river is used as the research object,the simulation modeling is carried out,and the correctness of the model is verified by the field data rated and actual operation.In view of the "weak protection" condition of the brushless exciter in the field,the basic analysis method of the fault of the rotating rectifying system based on the stator current of the exciter is proposed in this paper.Combined with simulation,the fault characteristics of two kinds of brushless exciter rotating rectifier are analyzed theoretically,and the harmonic characteristics of stator current under the normal and fault state of the rotating rectifier bridge are qualitatively analyzed.Both theoretical analysis and simulation results show that a large number of low harmonic currents will be induced in the stator current when a rotating rectifier is open,and the low harmonic content is obviously different from that in the normal condition.On this basis,and through quantitative simulation analysis,the on-line monitoring scheme and monitoring threshold of rotating rectifier system based on excitation stator current are obtained.In order to extract the air gap magnetic field characteristics of exciter more intuitively,the d axis detection coil and q axis detection coil are installed on the exciter stator.The inductive potential of the detection coil under normal and fault operation is simulated,and the simulation results are decomposed by Fu Liye.The results show that the harmonic characteristics of the induction coils are the same as the harmonic characteristics of the stator current,but the harmonic characteristics of the inductive potential of the detection coil are more obvious in the case of fault.A large number of low order harmonics are detected in the induction coil under the condition of one tube open circuit and one phase open circuit.Finally,based on the inductive potential of the probe coil,a fault monitoring scheme for rotating rectifier is proposed.The two on-line monitoring schemes provide an effective basis for the protection and on-line monitoring of the rotating rectifying system of the brushless exciter in the actual nuclear power project,and can realize the quick judgment of the open circuit and the open circuit of the rotating rectifying system of the brushless exciter.