Characteristic Analysis And Diagnosis Of Inter-turn Short Circuit Fault In Rotor Excitation Winding Of Large Synchronous Condenser

In order to realize long-distance and large-capacity power transmission,China has vigorously developed and constructed UHVDC power transmission projects.At the same time,the problem of insufficient reactive power support is prominent.Therefore,the development of new type adjustable camera with dynamic reactive power compensation ability has attracted much attention.The camera as a large rotary equipment,the rotor field winding interturn short circuit fault occur at higher risk,is not easy to identify early failure,if not for the timely and effective to solve,may cause the rotor one-point earthing or multipoint earthing and a series of more serious consequences,a serious threat to the safe operation of condenser and system,therefore,to ensure the security and stability of condenser operation,It is very important to propose an effective fault diagnosis method for the adjusting camera.The work done in this paper is as follows:(1)Based on the finite element theory and field circuit coupling principle,the finite element model of 300 MVar dual water cooled condenser under normal and excitation winding inter-turn short circuit fault is established.The correctness of the model is verified by the output torque,excitation current,terminal voltage,stator current,induced potential and phase under rated condition.Based on the principle of magnetic potential balance,the variation characteristics of rotor magnetic potential and air gap magnetic potential before and after the turn-to-turn short circuit fault of condenser excitation winding are analyzed and deduced,and verified by simulation.At the same time,combined with maxwell stress tensor method,and through simulation analysis,the relationship between the unbalanced magnetic pull and the fault degree,fault location and excitation current is calculated.The variation law of stator parallel branch circulating current before and after turn-to-turn short circuit is deduced and verified by simulation.(2)Based on the fact that the stator core axial direction of the camera is insulated to the ground,and the core-piercing screw and the supporting bar can be used as a natural detection sensor to reflect the variation characteristics of the main magnetic field,the diagnosis method of extracting the interturn short-circuit magnetic field features by using the core-piercing screw and the supporting bar instead of the detection coil is proposed.Use wear heart screw was deduced and the support mechanism of reinforcement for feature extraction of fault diagnosis,and then with the help of a condenser simulation,based on the finite element model under different excitation state under different degree of interturn short circuit fault and verified through a heart screw and support for the diagnosis of reinforcement effect,determine the threshold value of fault diagnosis,and the fault location of the screw wear heart function were studied.(3)Considering the dynamic the effects of the eccentricity of turn-to-turn short circuit diagnosis analysis derived the dynamic magnetic field characteristics of eccentric by camera,and is verified by the finite element simulation,and calculated the dynamic eccentric wear heart on the screw under the extraction percentage of even order harmonic voltage,prove the existence of dynamic eccentricity of exciting winding interturn short circuit in the diagnosis of interference;In view of the limitations of single fault feature diagnosis and the interference of dynamic eccentricity to interturn short circuit diagnosis,in order to improve the reliability of diagnosis results,an interturn short circuit fault diagnosis method based on D-S evidence theory was proposed and its effectiveness was verified.