Due to the electrostatic adsorption of DC lines, the pollution level of DC lines is higher than that of AC lines under the same conditions, and the number of insulators required is also more than that of AC lines. The insulation level is mainly determined by the pollution discharge characteristics of the insulator strings. Therefore, there are two main methods when selecting the number of insulators:
1. According to the artificial pollution test of insulators, the insulator pollution tolerance method is used to measure the pollution flashover voltage of insulators under different salt densities, so as to determine the number of insulators.
2. According to the operating experience, the creepage distance method is adopted. In general, the creepage distance of DC lines is twice that of AC lines. Among the two methods, the former is intuitive, but requires a large amount of testing and testing data, and the results of testing and testing are highly dispersed. The latter is simple and easy to implement, but less accurate. In practice, usually a combination of the two