The Characteristics of pad-mounted distribution transformer integrages the transformer active part, high-voltage load switch, protective fuse and other facilities in the same sealed oil tank,therefore the volume is small, and it is widely used in industrial parks, residential areas, various places such as commercial centers and high-rise buildings. The conventional structure is devided into "L" type, parallel configuration, πconfiguration, compact type, pavilion multi-functional type, etc, can comply terminal, ring network and dual-power supply method functions which can be correspondingly complied high-voltage metering, phase loss protection functions.