Dry-type transformers refer to transformers whose iron cores and windings are not immersed in insulating oil. They are widely used in residential quarters, high-tech centers, factories and mines, airports, stations, schools and other places. This series of dry-type transformers are used to directly reduce 35KV electrical grid power supply to 400V distribution power supply for users and omits the stage of 10KV transmission and transformation., which significantly decreases operating costs and engineering construction costs of multi-level substation projects, and have significant social benefits. By optimizing the structure of the high-voltage coil, the distributions of voltage and capacitance between layers are improved, which greatly enhances the impact resistance of products to withstand atmospheric over-voltage and operating over-voltage, as well as improves the electric field distribution and further reduces the partial discharge volume of product.