The interior of the box is divided into two parts: bus room and cable bin by cable silo roof plate. The bus room is a sealed chamber made of 2mm steel plate. The cable connector bracket is located at the upper part of the bus room and is used to support the casing, which is used to secure the cable connection, with an interphase distance of 180mm. In the case of a lightning arrester type, the rear of the cable connector mounted by the arrester. In addition, short-circuit indicators and live displays are also installed in the bus room. All live parts of the bus room are subjected to strict silicone rubber outsourcing insulation. The cable bin is located under the bus room, is the passage of the cable in and out, and there are cable clamps and grounding terminals in the cable bin.