This type of transformer can go deep into the load center, and has the features of flame-retardant, explosion-proof, free from pollution. It applies the epoxy casting mode and therefore has high mechanical property, and strong withstand of short-circuit, running safely, low loss, efficient power-saving. The loss is 40% lower than that of the three-phase dry-type power transformer which has the same capacity, low noise, small size and easy installation, free from maintenance and the partial discharge is near to zero, high insulation level and low temperature fluctuant and long use.