In order to better adapt to the new situation of economic, social and power grid development, improve the power supply capacity and adaptability of the distribution network, reduce the loss and power supply cost of the distribution network, save land resources, and meet the development needs of the power system for "boosting, increasing capacity, upgrading and optimizing the channel", On the basis of digesting and absorbing foreign advanced technologies and design concepts, our company has designed and manufactured YBM-24/0.4 series of "HV/LV prefabricated substation" (European box type substation) with 20kV distribution voltage grade, in which high-voltage switches, transformers and low-voltage switches are pre installed in the substation. High voltage switchgear shall be selected according to the principle of small size, oil-free, good performance, high reliability, maintenance free or less maintenance, which can realize terminal or looped network operation. The power distribution transformer shall be energy-saving and environment-friendly (low loss and low noise) transformer with Dyn11 connection group, tap and 20kV power supply. The product has the advantages of high power supply reliability, reasonable structure, flexible installation, convenient operation, small size, low cost, etc. It is used in the system with high voltage of 20kV, especially in the current 20KV system, and can be directly used after the system is transformed to 20KV. It can be widely used in industrial and mining enterprises, airports, stations, residential areas, ports, highways, subways and other places in the urban network transformation.