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Box-type substation is a kind of high-voltage switchgear, distribution transformer and low-voltage distribution device. It is a factory prefabricated indoor and outdoor compact distribution equipment arranged into one body according to a certain wiring scheme, that is, the functions of high-voltage power supply, transformer step-down and low-voltage distribution are organically combined together. Installed in a moisture-proof, rust-proof, dust-proof, rat-proof, fireproof, anti-theft, heat insulation, fully enclosed, movable steel structure box, mechatronics, fully enclosed operation, especially suitable for urban network construction and transformation, is a new substation after the rise of civil substations.

Let's take you to analyze how to choose the right box-type substation.

1. According to the importance of the engineering power load and the high voltage power supply at the construction site, determine the high voltage line voltage level of the box-type substation.
2. according to the short-circuit capacity of the power grid system, line impedance and other parameters of the short-circuit current calculation, in order to determine the power supply components.
3. load calculation, and consider the appropriate margin after selecting the capacity of the transformer.
4. according to the user situation and environmental conditions to choose the appropriate transformer category (ordinary oil-immersed transformer, sealed oil-immersed transformer, dry transformer, etc.).
5. according to the load, select the appropriate number of low-voltage outlet circuit, determine the capacity of the low-voltage circuit breaker, and reserve the appropriate backup outlet circuit.
6. the selection of the site should be as close to the load center as possible, reduce the length of the inlet and outlet cable, and should consider the convenience of the inlet and outlet line, easy maintenance and does not affect the landscape environment and other factors.
7. according to the installation environmental conditions to take measures to prevent flooding.
8. do a good job of grounding device installation.
9. the basic approach and equipment installation should meet the requirements of the selected box substation product information.

Advantages of different structures of box-type substation

According to the different structure and the different components used, the box-type substation is divided into two typical styles: European box-type and American box-type.

The first point: analysis from the structure

From the structure of the use of high and low voltage switchgear, transformer composition, this box-type substation is called European box transformer. It is compared to building a house for high and low voltage switchgear and transformer.

In the structure, the load switch, ring switch and fuse structure are simplified into the transformer tank immersed in oil, the arrester is also oil-immersed zinc oxide arrester, the transformer cancels the oil cushion, the tank and the radiator are exposed to the air, this box-type substation is called the American box transformer. It's like hanging a box next to a transformer.

Second point: Compare by volume

From the volume point of view, the European box changes due to the internal installation of conventional switchgear and transformers, the product volume is larger. The American box is smaller due to the integrated installation.

Third point: comparative analysis from the aspect of protection

From the protection aspect, the load switch and current limiting fuse protection are used on the high voltage side of the European box. When a phase fuse is blown, the firing pin of the fuse is used to make the load switch switch at the same time to avoid phase loss operation, and the load switch is required to have the ability to cut off the transfer current. The low voltage side uses the load switch and current limiting fuse protection, and the high voltage side of the American box uses the fuse protection, and the load switch only has the function of switching and cutting off the high voltage load current, and the capacity is small. When a phase fuse is blown on the high voltage side, the voltage on the low voltage side is reduced, and the under-voltage protection or over-current protection of the MCCB automatic air switch will act, and the low voltage operation will not occur.

Summary: On the whole, the European box transformer has high cost. From the perspective of product price reduction space, there is still a large price reduction space for American box change. On the one hand, the American box change three-phase five-column core can be changed to three-phase three-column core. On the other hand, the high pressure part of the American box change can be modified from the transformer tank to the outside of the tank, occupying the high pressure chamber space.