Research On The Electric-Thermal Field Of Stator Major Insulation Of Air-cooled Turbine Generator

With the continuous improvement for single unit capacity and rated voltage level of large air-cooled turbogenerator,the requirement for the performance of insulation system is getting higher.Not only does the stator major insulation of large generators meet the requirements of electrical and mechanical performance in normal operation,it also faces the tests of various complex operation environments such as high voltage and high heat etc.With the long-term operation under the environment of high electricity,heat load and vibration,the stator major insulation of large generator is likely to be delaminated or emptied,and cause the partial discharge of stator insulation.The process of repeated discharge of insulation will further enlarge the gap of the shelling,damage the life of insulation,and seriously impact the safe operation of the generator.Therefore,it is necessary to research the electric field and temperature field of stator major insulation under the normal and abnormal conditions.This thesis takes a 150MW air-cooled turbogenerator as an example.First,according to the actual structure size of the generator,the 2D electric field model of two half teeth and a slot in the stator of generator is established,and the electric field distribution of stator major insulation is analyzed under the normal and abnormal conditions.The relative permittivity is calculated according to the different thermal aging degree of the major insulation,and the effect of relative permittivity change on the electric field of the major insulation is calculated and analyzed.The stator major insulation is further researched on the influence of stator insulation with the 4 kinds of shelling structures which are the single-side shelling ?=0.5mm and ?=1.0mm,bilateral unequal distance shelling?1=0.5mm,?2=0.3mm and ?1=1.0mm,?2=0.5mm on the electric field of major insulation.Secondly,according to the relevant theory of electric field and the actual structural of the stator winding,a 3-D finite element model of electric field is established,which includes two iron core segments and a radial ventilation groove along the axial direction,and two half teeth and a whole slot along the circumferential direction.The 3-D electric field finite element model is used to study the effect of air humidity change(air conductivity from Os/m to 3.0s/m)on the electric field in the stator radial ventilation groove.The electric field variation law of the stator major insulation is studied when the major insulation is shelled at 6mm,5mm and 4mm respectively at different positions along the radial direction,and the effect of shelling at 5mm in different positions along the axial direction on the electric field is also studied.Finally,based on the theory of fluid field and temperature field,a 3-D fluid-solid coupling model including a radial ventilation groove,two half teeth and a whole slot is established.The major insulation of the straight section of the stator winding is calculated and analyzed in normal,single-sided shelling and bilateral unequal distance shelling operations.The relationship between the temperature distribution of the major insulation of stator and the degree of shelling,the type of shelling and the thermal conductivity of the major insulation is obtained.By studying the temperature distribution of air in different gaps of the major insulation of the stator,the relationship between the temperature of the air in the gaps and the degree of shelling and the type of shelling are further obtained.