Analysis on the Amplitude and Frequency Characteristics of the Rotor Unbalanced Magnetic Pull of a Multi-Pole Synchronous Generator with Inter-Turn Short Circuit of Field Windings

Abstract

Inter-turn short circuit of field windings (ISCFW) is a common generator fault which can result in serious safety accidents for power systems, if the fault is not eliminated in time. Taking advantage of the electrical and mechanical characteristics of the generator after a fault as a fault criterion is a new idea for fault monitoring, so finding out the frequency and amplitude frequency characteristics of rotor unbalanced magnetic pull (UMP)—the vibration excitation source of the fault—is the basis and key of the research. Taking a six-pole generator as an example, the effects of harmonic magnetic motive force (MMF) interaction on rotor UMP, as well as the frequency characteristics of rotor UMP after generator faults in different stator windings, are obtained based on the analysis of the air-gap MMF of the generator after a fault, and the results of theoretical analysis are verified by simulation. Based on the above results, the simulation calculation on rotor UMP of generators with three stator winding forms under different operating conditions has been achieved, to get the relation between rotor UMP amplitude and active power and field current, and to find out the mechanism of rotor UMP amplitude change along with operating conditions and effect of stator winding forms on UMP amplitude by theoretical analysis. The conclusions are of important significance for studying fault mechanical characteristics of generators and lay a foundation for online monitoring on ISCFW by integrating mechanical and electrical information.