Due to the mandatory use of standardized cabinets in the past to avoid type testing, four low-voltage cabinets are generally installed in low-voltage rooms, forming iron cabinets with a small appearance. Looking back at foreign products, the high-voltage side is an SF6 switchgear, and the low-voltage side is not installed in the cabinet but directly assembled with components, resulting in a very small volume.
In order to consider the legitimacy of the development of domestic box transformers into small box transformers and the assembly of electrical components, the following content has been specially added to Article 5.7 of the DL/T537-2002 "Guidelines for the Selection of High Voltage/Low Voltage Prefabricated Box type Substations (Implemented on September 1, 2002)" in the power industry standard:
If simplified switchgear and control equipment assembled from electrical components are used, there should be enclosed intervals and doors made of metal plates. If there are exposed live parts after the door is opened, necessary protection should also be taken. The board or framework used for installing electrical components should have sufficient strength and stiffness, and the installation position of electrical components should be convenient for installation, wiring, testing, maintenance, and operation. The simplified switchgear and control equipment used shall undergo type testing in accordance with the requirements of DL/T404 and GB7251.1.