Search

As the core of large-capacity nuclear power generation system, the multiphase annular brushless exciter (MPABE) may cause a serious catastrophe to the nuclear power plant if it fails. In order to effectively protect the armature winding of MPABE, a rapid simulation model and a sensitive diagnosis method of armature winding short-circuit (AWSC) fault are studied systematically in this article. First, this article proposes a general and rapid simulation model of MPABE with AWSC fault. To verify the correctness of this model, corresponding simulations and experiments of AWSC faults are carried out, respectively, through which the fault characteristics are obtained. Then, a detailed mechanism analysis is presented, which explains the induction process of the related harmonics in the stator and rotor currents. The variation law of the characteristics value when the number of short-circuited coils changes is also analyzed. Finally, a new method to diagnose AWSC fault of the MPABE is proposed and then optimized. The test results on the prototype show that this method can sensitively diagnose even the slightest AWSC fault. Therefore, it can provide a reliable basis for the monitoring and protection of MPABE in nuclear power plants. [ABSTRACT FROM AUTHOR]

The excitation system with a multi-phase annular brushless exciter (MPABE) is widely used in large-capacity nuclear power plants. It is of great significance to realize a reliable protection of the exciter for safe operation. Since the MPABE is adopted with rotary armature structure, the rotor winding short-circuit (RWSC) fault is very difficult to be diagnosed directly. However, it is an effective way to realize fault diagnosis through the characteristics reflected in the stator field winding. In this paper, based on the mutual induction relationship between stator current and rotor current, detailed theoretical analysis of the RWSC fault is conducted and the harmonic characteristics of the stator field current are obtained. Then, related experiments and simulations are carried out, verifying the correctness of the theoretical analysis. Finally, a diagnosis method based on the transient harmonic characteristics of the stator field current is proposed and its sensitivity is also analyzed. The diagnosis method proposed in this paper is simple and feasible, which helps to improve the safety and reliability of the MPABE system in nuclear power plants. [ABSTRACT FROM AUTHOR]

A machine learning-based approach is proposed to predict the transient stability of power systems after a large disturbance. The post-disturbance trajectories of generator rotor angles are taken as a whole cluster, and 19 cluster features are defined to depict the overall transient stability characteristics of the power systems. A hybrid approach, which combines the linear support vector machine with the decision tree, is proposed to generate the final transient stability classifier. Comprehensive studies are conducted on the IEEE 39-bus and IEEE 145-bus test systems to verify the performance of the proposed approach. Test results show that by using the cluster features and the proposed approach, the transient stability of the power system can be predicted accurately with a shorter training time. Furthermore, the prediction classifier is robust to unknown load levels and network topologies, especially under situations when some generator measurements are unavailable and the number of input cluster features is independent of the system scale, making the proposed approach more suitable to transient stability prediction of large-scale power systems. [ABSTRACT FROM AUTHOR]

This paper studies the electromagnetic torque (EMT) of a nonsalient-pole synchronous generator with the interturn short circuit of field windings (ISCFW). First, the virtual displacement method serves as a basis for analyzing the postfault steady-state harmonic characteristic of EMT. The interactions among various space magnetic fields with different orders, speeds, and rotation directions generated by the stator and rotor are considered. A general conclusion on the EMT characteristics under the fault is then derived. Second, based on the connection conditions of the rotor and stator windings under the fault, the voltage and flux relationships among each circuit are analyzed and the calculation model of the EMT under the fault is built. Through comparisons among the simulations, experiments, and theoretical analyses, the correctness of the calculation model is verified. In addition, a three-pole-pair nonsalient-pole synchronous generator after transformation is used for the case study. The calculation and analysis results indicate that ISCFW generates ac pulsation components with their harmonics closely linked to the stator winding configuration. This paper deepens the fault mechanism of ISCFW and lays a foundation for fault monitoring based on mechanical characteristics. [ABSTRACT FROM AUTHOR]