Hydro Generator Stator Bar Modeling and Simulation Based on Finite Element Simulation

Abstract

As motor capacity and rated voltage increase, the demand for motor insulation also increases. Additionally, the electric field distribution at the end of a large-scale hydro generator is extremely nonuniform, and corona discharge occurs. This destroys the main insulation, which significantly affects the service life of electrical machinery. The regulation of the electric field concentration at the end of a large-scale hydro generator needs to be addressed. In this manuscript, a large hydro generator with 120 MW rated capacity and 15.75 kV rated voltage was studied. For the purpose of electric field homogenization in the stator bar end, decrease of highest field strength, and surface loss, the computing methods of the electric field in the stator bar end were studied. The electric field distribution in the stator bar end was obtained. According to COMSOL 5.6 modeling software, the hydro generator stator bar is an accurate model. Using finite element analysis (FEA), the stator bar characteristics can be simulated. The different stator bars with no anti-corona structure, linear anti-corona structure, two-layer nonlinear anti-corona structure, and three-layer nonlinear anti-corona structure were compared, including the electric potential, electric field, and loss distribution under rated voltage. From the experimental results, with no anti-corona structure and linear anti-corona structure, the electric field concentration is present in the exit slot. The values of electric field and loss are both higher, which causes corona discharge easily. With the nonlinear anti-corona structure, the electric field concentration is improved significantly, effectively decreasing the highest electric field. The three-layer nonlinear anti-corona structure is the best. Compared with the two-layer nonlinear anti-corona structure, the values of the highest electric field and loss are 16% and 77% lower, respectively.