Simulation and Testing Research of Thermo-electric Field for Large Generator Stator Bar End in Hipot Test

The non-linear characteristic between anti-corona material and thermal field is researched deeply based on the fact that burning damage causing by overheat for large generator stator bars takes place frequently during the hipot (high potential) test. The non-linear relationship between loss density and electrical field as well as thermal field is determined. Couple solving model is established for stator bar end parts during hipot test. It is proved from theory and experimental means that simulating method is corrected. By using this simulation method, the temperature distribution of wire rods with three different anti-halation structures is studied. It can be seen that the maximum temperature of wire rods increases sharply with the increase of the medium resistance length. When the medium resistance length reaches 11cm, the narrow edge of the wire rod shows signs of overheating, resulting in an aging channel in the anti-halation area and extending to the high resistance area, which is in good agreement with the test results. The impact of anti-corona construction to dielectric strength, loss density and temperature is researched deeply. The results demonstrate that the highest temperature along stator bar end parts appears on the edge angle of overlap joint between medium-resistant anti-corona parts and low-resistant anti-corona parts. Partial anti-corona parts will be aging causing by excessively high temperature and this will create aging pathway along the narrow edge of the stator bar, which leads the temperature rising with wide range. Designing optimization point is existed for loss density. If the design of anti-corona construction is near the optimization point, the temperature of the stator bar end parts will be reduced effectively.