Box-type substation is a set of compact distribution transformers,High pressure ring mesh cabinets, Electric energy metering equipment and reactive power compensation device, according to a certain wiring scheme combined into one or more box type. Suitable for three-phase AC system with rated voltage 10/0.4KV, as a line and distribution power supply.
Compared with European box transformers of equal capacity, the structure of box-type transformers in the United States is more reasonable. Because the European box transformer is the transformer and ordinary high-voltage electrical equipment installed in the same metal shell box, due to the transformer's high room temperature, heat dissipation difficulties, affecting the output; On the other hand, due to the use of ordinary high VO, box-type transformer volume is larger. Load switches, fuses and low-voltage switchgear in the T-box. The American box variable is structurally different from the European box variable. From the layout point of view, low-pressure room, transformer room and high-pressure room is not directory layout, but classification layout. From the structural point of view, this junction box can be divided into the front and back two parts, with high and low pressure operating intervals. The operating intervals include high and low pressure terminals, load switch handles, no-load pressure-regulating segmented switches, plug-in fuses, oil level gauges, etc., the rear is the fuel tank and radiator, the transformer winding, core, high-voltage load switch and fuse into the transformer fuel tank.
Oil-immersed metal oxide arresters are also used in lightning arresters. The transformer cancels the oil pillow and designs the sealed fuel tank by the principle of equal capacity filling oil and gas gap. Fuel tanks and radiators are exposed to air and heat dissipation is not difficult. Low voltage circuit breaker uses plastic shell circuit breaker as main circuit breaker and outlet circuit breaker. Due to the simplification of the structure, the area and volume of the box substation are greatly reduced. Because of the small size of the box substation, only one side door, the required area is only 1/4 of the European box substation, the capacity of the box-type substation is only the same capacity of the European box substation 1/5-1/3. The United States box variable pressure side using fuse protection, low-pressure side of the use of plastic shell automatic air circuit breaker protection, and China's 10kV distribution transformer the same. The high voltage fuse protects the internal fault of the transformer, and the automatic air circuit breaker protects the overcurrent, short circuit and undervoltage fault of the low-voltage side line. The shortcomings of the American box have changed. Because the load switch is immersed in oil, the oil is decomposed by arc carbonization, producing harmful gases such as acetylene, reducing performance and causing accidents. Due to the absence of obvious breakpoints, maintenance is not convenient. Since low-voltage protection and measurement methods in the United States are different from China's low-voltage protection and measurement methods, the United States box-type transformers themselves do not carry out low-voltage protection and measurement. In order to meet the needs of domestic users, low-voltage distribution cabinets installed in the domestic box of low-pressure side. Because the box circuit breaker is in direct sunlight for a long time, which affects the heat dissipation of the plastic shell circuit breaker, the circuit breaker can not interrupt the load and short-circuit current normally, and it is easy to cause high pressure side fault.