Box substation, also known as preinstalled substation or preinstalled substation. Is a high voltage switchgear, distribution transformer and low voltage distribution device, according to a certain wiring scheme into one of the factory prefabricated indoor and outdoor compact distribution equipment, that is, transformer step-down, low voltage distribution and other functions are organically combined together, installed in a moisture-proof, rust-proof, dustproof, rat-proof, fire, burglar, heat insulation, fully enclosed, movable steel structure box, Especially suitable for urban network construction and transformation, is a new substation after the rise of civil substation. Box substation is suitable for mining, factories, oil and gas fields and wind power stations. It replaces the original civil power distribution room and power distribution station and becomes a new complete set of transformer and distribution devices.

Principle of

Box-type substation (hereinafter referred to as box-type substation) is a compact complete set of distribution devices that combine high-voltage switchgear distribution transformer, low-voltage switchgear, electric energy metering equipment and reactive power compensation device in one or several boxes according to certain wiring schemes. It is suitable for the rated voltage 10/0.4KV three-phase AC system, as a circuit and distribution of power.

Compared with the European box with the same capacity, the structure of the American box is more reasonable. Because the European type box transformer is the transformer and the common high voltage electrical equipment installed in the same metal shell box, the transformer room temperature is very high, causing heat dissipation difficulties, affecting the output; On the other hand, common high voltage load switch and fuse and low voltage switch cabinet are used in the box body, so the volume of European box is large. The American box is different from the European box in structure. From the layout, the low voltage room, transformer room, high voltage room is not the layout, but the product layout. In terms of structure, the box type is divided into two parts: the front and the back, and the front is the high and low pressure operation interval. The operation interval includes the high and low pressure terminal, the load switch handle, the no-load voltage regulating switch, the plug-in fuse, the oil level meter, etc. The back is the fuel injection tank and heat sink, and the transformer winding, core, high voltage load switch and fuse are put into the transformer oil tank.

The arrester also uses oil - immersed metal oxide arrester. The transformer cancels the oil pillow and adopts the principle of constant volume of oil and air gap to design the sealed oil tank. The oil tank and radiator are exposed to the air and there is no difficulty in heat dissipation. The low voltage circuit breaker uses the plastic shell circuit breaker as the main circuit breaker and the outlet circuit breaker. Due to the simplified structure, the area and volume of this box substation are greatly reduced. Due to its small size and only one side of the door, the required area is only 1/4 of the European box transformer, and the volume is only 1/5-1/3 of the European box transformer with the same capacity. The high voltage side of American box transformer is protected by fuse, and the low voltage side is protected by plastic shell automatic air circuit breaker, which is the same as the protection mode of Chinese 10kV distribution transformer. High-voltage fuses protect the internal faults of the transformer, and automatic air circuit breakers protect the over-current, short-circuit and undervoltage faults of the lines on the low-voltage side. The disadvantages of American box change. Because the load switch is immersed in the oil, the oil is carbonized and decomposed by the arc, producing acetylene and other harmful gases, which makes the performance decline and has occurred accidents. No obvious disconnection point can be seen, and maintenance is not convenient. Because the United States low voltage protection and measurement method is different from China, the American box transformer itself does not have low voltage protection and measurement. In order to meet the needs of domestic users, the domestic box transformer is equipped with low voltage distribution cabinet on the low voltage side. Because the box transformer is under the direct sun for a long time, the heat of the plastic shell circuit breaker is affected, so that the circuit breaker can not normally open the load and short circuit current, which is easy to cause the fault of the high voltage side.