The main insulation of the stator bar is subjected to the combined action of multiple stresses during operation

and its dielectric properties have an important impact on ensuring the safe operation of the generator. Based on the calculation theory of composite dielectric constant

a simplified model of main insulation of generator stator bar is established

and the calculation method of main insulation dielectric constant is given. The test calculation method of the main insulation dielectric constant of the generator stator bar is obtained which is suitable for the fillet electrode structure. According to the size parameters of the stator bar and the capacitance obtained by the test

the actual dielectric constant of the main insulation can be calculated. On this basis

the accuracy of the proposed method is verified by comparing the results of model test bar dielectric constant test and theoretical analysis.