A box-type substation-also known as a prefabricated substation or packaged substation-is a compact, factory-prefabricated power distribution unit designed for both indoor and outdoor use. It integrates high-voltage switchgear, distribution transformers, and low-voltage distribution equipment into a single assembly based on a specific wiring scheme. Essentially, it organically combines functions such as voltage step-down and low-voltage distribution within a fully enclosed, mobile steel enclosure that is resistant to moisture, rust, dust, rodents, fire, and theft, while also providing thermal insulation. This type of substation is particularly well-suited for the construction and modernization of urban power grids; it represents a new generation of substations that has emerged as a successor to traditional civil-engineering-based substations. Box-type substations are applicable to mines, industrial facilities, oil and gas fields, and wind power stations; they serve as modern, complete sets of power distribution and transformation equipment, replacing traditional civil-engineering-based distribution rooms and substations.
Box-type substations are suitable for use in residential communities, urban public power distribution networks, bustling commercial districts, and construction sites requiring temporary power supplies. Users can select the appropriate box-type substation model based on specific operating conditions and load requirements. Since their inception, box-type substations have experienced rapid growth; in developed European nations, they now account for 70% of all distribution transformers, while in the United States, this figure stands at 90%. Given the rapid pace of urban modernization in China and the continuous upgrading and renovation of its urban power distribution grids, box-type substations are poised for widespread application throughout the country.
Regarding the development of box-type substations in China: beginning in the late 1970s, China introduced and reverse-engineered designs from countries such as France and Germany. Structurally, these early models consisted of separate high-voltage switchgear, low-voltage switchgear, and transformers assembled together. This configuration is known as the "European-style" box-type substation-aptly visualized as essentially building a protective "house" over the high-voltage switchgear, low-voltage switchgear, and transformer components. Starting in the 1990s, China introduced the American-style box-type substation design. Structurally, this design simplifies the arrangement of load switches, ring-network switches, and fuses by housing them within the transformer tank, where they are immersed in oil. Similarly, the surge arresters utilized in this design are of the oil-immersed zinc oxide type. Furthermore, the transformer eliminates the traditional oil conservator (expansion tank), leaving the main transformer tank and radiators exposed to the ambient air. This configuration is referred to as the "American-style" box-type substation-vividly described as simply attaching a control cabinet to the side of the transformer.
