Features: S11-MD-underground distribution transformer core cold-rolled silicon steel miter joints using low-loss step-stack from the system. High and low voltage coil using cylindrical and spiral wound structure. Transformer low voltage side of the watertight box structure using high-pressure side of the head with waterproof cable products with anti-pollution, water and strong, no-load current, low noise, low loss, low temperature characteristics, the product can be charged continuously run for a certain time soaking advantages. Advanced technical indicators, unique structure, exquisite appearance, is particularly suitable for a water environment such as underground tunnels of a high-tech, high-performance energy-saving products.