An underground box-type substation refers to a substation where the entire set of equipment is installed inside a fully sealed box and the entire system is placed below ground level. It is the same as the box-type substation above ground, with internal equipment being identical. The substation steps down the 10kV input voltage to 400/220V distribution voltage through a transformer and then delivers the power to load points. It can be used in ring network distribution systems and also as a substation for supplying power to terminal points in radial power grids. This fully underground type is also known as an underground substation. The box structure offers excellent corrosion resistance and compression resistance, with absolute sealing capabilities.