The 10kV fully sealed three-dimensional wound core distribution transformer is an energy-saving distribution transformer promoted nationally. The current models, S13, S20, and S22, correspond to Level 3, Level 2, and Level 1 energy efficiency, respectively. The three-dimensional wound core is a breakthrough from the traditional planar core structure, consisting of three single core frames formed by continuously winding trapezoidal material strips, assembled into a three-phase symmetrical three-dimensional structure. Compared to traditional transformer cores, it offers features such as three-phase balance, material savings, low no-load losses, low no-load current, strong short-circuit resistance, low noise, and reduced electric and magnetic fields. It has low operating costs, a long service life, and significant energy-saving effects.