Rated voltage refers to the optimal voltage for electrical equipment to operate normally for a long time, and the rated voltage is also known as the nominal voltage. When the working voltage of electrical equipment is higher than the rated voltage, it is easy to damage the equipment, and when it is lower than the rated voltage, it will not work properly (such as abnormal light emission of bulbs and abnormal operation of motors). Rated voltage is the standard voltage for long-term stable operation of electrical equipment (including electrical and power supply equipment). The rated voltage can be understood from both the electrical equipment and the power supply equipment. The rated voltage of the electrical equipment represents the optimal input voltage designed at the factory, which is usually a relatively easy to obtain power supply voltage. The rated voltage of power supply equipment represents the optimal output voltage of the power supply system, which needs to be matched with the rated voltage of the electrical equipment, including the rated voltage of the power grid, the rated voltage of the generator, and the rated voltage of the power transformer. At rated voltage, electrical equipment, generators, and transformers have the maximum economic benefits during normal operation. At this point, all components in the equipment are working in their optimal state, with stable performance and relatively long lifespan. The rated voltage of designated electrical equipment is conducive to the standardization and serialization of production in the electrical manufacturing industry, the standardization and selection of design, the interconnection and replacement of electrical appliances, and the production and maintenance of spare parts. In addition, in order to avoid the unlimited expansion of voltage levels, which leads to difficulties in interconnection, it is necessary to standardize the rated voltage of the power grid. To achieve the best technical and economic performance, power equipment needs to be optimized for design, manufacturing, and use at rated voltage. The voltage of the power grid is graded, and there are significant differences in the rated voltage of power equipment at all levels of the power grid. The rated voltage level of the power grid is formulated and promulgated by the state after comprehensive analysis and demonstration based on factors such as the needs of national economic development, the rationality of technology and economy, and the manufacturing level of electrical equipment