At present, kyn28a-12 type central type switch cabinet is the mainstream product of 12kV distribution network. Since 1998, Longding Electric has begun to develop and produce this product. With the continuous increase of its application, more and more complete sets of manufacturers have begun to develop and produce this kind of product through technology transfer and other forms, and put a large number of them into power grid use. According to statistical data, at the end of 2015, kyn28a series products were 627806, and more than 100 domestic manufacturers have the production capacity of this equipment. With the continuous optimization, upgrading and upgrading of different manufacturers, there are certain differences in product structure and interface between different manufacturers, which makes it impossible to exchange them. Therefore, there are big problems in operation, maintenance and expansion when the equipment fails on site, In particular, since the State Grid Corporation of China fully implemented the "three sets and five major" system construction, the implementation of the agreement inventory bidding procurement system has become increasingly prominent. In order to meet the common and interchangeable use of different manufacturers' equipment in a certain range and a certain period of time, and improve the operation and maintenance convenience of switchgear equipment, the State Grid of China has proposed the standardized design of kyn28a since 2016, In the future, the handcart type high voltage switchgear in the State Grid bidding must meet the requirements of standardization.