Mixed Eccentricity Fault Diagnosis in Salient-pole Synchronous Generator Using Modified Winding Function Method

In this paper, winding function method (WFM), applied to a faulted synchronous generator, is modified and is used for online diagnosis of mixed eccentricity fault. For the first time, the static and mixed eccentricities are modeled in synchronous generators. A modified winding function (MWF) method introduced here is more precise compared with previous methods. This MWF enables to compute the air gap magnetic permeance accurately. Here, two or three terms of the infinity permeance series have not been used, but a closed form equation is employed for permeance evaluation. This leads to a very precise computation of the inductances of the faulted machine. Self inductances of the stator and rotor, mutual inductance of two stator phases and the mutual inductance of rotor and stator are obtained. Meanwhile, it is shown that static, dynamic and mixed eccentricities lead to the increase of the amplitude and occurrence of the distortion in the aforementioned inductances. Since calculation of inductances is the most important step for fault diagnosis of the machine, the proposed method improves the on-line diagnosis of the fault. Meanwhile, the spectrum analysis of stator current, obtained from experimental results, is illustrated.