American type Compact transformer, also named Preinstalled substation or American box substation, is suitable for multi-storey residential buildings and other unimportant buildings with relatively low power supply requirements.  According to our actual use, American box with small ring network switch station, fully suitable for multi-storey residential power demand.  Fighting against the box change failure, the impact on residents is not big, but not suitable for small high-rise and high-rise. The answer is from a customization upon request compact substation factory called SPL.