Abstract: The operating environment of transmission lines is vast and complex, and it is inevitable to pass through some special areas, such as overweight pollution areas. Under the overweight pollution environment, the pollution flashover of transmission line insulator strings occurs repeatedly, and the insulation configuration and composite treatment of insulators according to the e-level pollution upper limit have not yet solved the pollution flashover problem. Therefore, we verified and calculated the insulation configuration of transmission lines through a 500 kV transmission trip fault, aiming to propose methods for verifying and optimizing the insulation configuration of transmission lines in overweight pollution environments. Firstly, we conducted pollution level and pollution flashover voltage tests on line insulators in overweight pollution environments. Based on the test results, the insulation configuration of transmission lines was verified. Moreover, a pollution flashover model suitable for heavy pollution conditions was proposed. Research reveals that the pollution level in areas where pollution flashover occurs is very severe, with the highest salt density value of suspension string composite insulators reaching 1.136 mg/cm², which is far higher than the current standard pollution level in the distribution of pollution areas. Secondly, high pollution can easily lead to a decrease in the hydrophobicity and migration performance of the anti-fouling flashover of RTV coating. Snow or icing can easily cause a brief loss of hydrophobicity of the RTV coating. In this environment, the use of anti-fouling flashover coating should be re- checked for insulation configuration. Finally, by correcting the effective conductivity of the insulator surface and the arc characteristic constant of the calculation model, the average error of the flashover model under heavy pollution was reduced from 20.16% to 11.11%, reducing the error of the verification calculation. The research results of the paper provide important reference basis for the calculation of line insulation configuration in high pollution environment areas in the future.