Abstract
This paper investigates the radial stator vibration characteristics of turbogenerator under the static air-gap eccentricity (SAGE) fault, the rotor interturn short circuit (RISC) fault, and the composite faults (CFs) composed of SAGE and RISC, respectively. Firstly, the impact of the faulty types on the magnetic flux density (MFD) is analyzed, based on which the detailed expressions of the magnetic pull per unit area (MPPUA) on the stator under different performing conditions are deduced. Then, numerical FEM simulations based on Ansoft and an experimental study are carried out, taking the SDF-9 type fault simulating generator as the study object. It is shown that SAGE will increase the stator vibration at 2f(fis the electrical frequency) which already exists even in normal condition, while RISC and CF will bring in stator vibrations atf, 2f, 3f, and 4fat the same time. The vibration amplitudes under CF are larger than those under RISC. As SAGE increases, the vibration amplitudes of each harmonic component under CF will all be increased, while the development of RISC will decrease the 2nd harmonic vibration but meanwhile increase the 4th harmonic vibration. The achievements of this paper are beneficial for fault identification and condition monitoring of the turbogenerator.
Highlights
static air-gap eccentricity (SAGE) and rotor interturn short circuit (RISC) are common faults of turbogenerator
Achievements obtained for SAGE mainly focus on the three-phase current or voltage change [3,4,5,6], the circulating current inside parallel branches (CCPB) and its corresponding diagnosis method [7,8,9], the unbalanced magnetic pull (UMP) calculation via FEM [10, 11], the winding inductance variation based on improved winding function theory [12], and so forth
The stator vibration amplitudes at f, 2f, 3f, and 4f under CF condition will be more intense than under RISC condition. This can be used for the fault identification among the single and the composite faults composed of SAGE and RISC
Summary
SAGE and RISC are common faults of turbogenerator. When the eccentricity degree is more than 10%, severe vibrations, stator core deformations, and even winding damage will be caused [1]. When RISC fault develops progressively, serious consequences, such as field current increment, reactive power output decrease, and bearing vibration aggravation, will be produced. It may develop into an earth fault and magnetize the rotor. Which have usually been already set up inside the generator or by setting sensors outside the generator conveniently, while the EMT can be calculated by using the phase voltages, currents, and the rotating speed of the rotor which can be obtained without installing extra sensors [19]. Since SAGE exists in almost every generator, there is a CF occurring when RISC takes place Previous studies on this kind of CF found that the failure characteristics are different from those of the single SAGE and RISC faults [20]. The whole work is taken based on the theoretical analysis, the numerical FEM simulation, and the experiment study
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