YBD1-12/0.4 Underground substation

1. Altitude: The altitude shall not exceed 1000 m.
2. Ambient Temperature: Maximum temperature: +40°C; minimum temperature: -30°C.
3. Relative Humidity: At 25°C, the relative humidity of the air shall not exceed 95%, and the monthly average shall not exceed 90%.
4. Installation Environment: The installation site shall be free from obvious pollution, explosive or corrosive gases, and dust. The installation site shall be free from severe vibration and impact and shall not be located in a low-lying area.
5. Special Service Conditions: Other service conditions beyond the above normal service conditions shall comply with the provisions of GB1094.1, GB/T11022, GB/T14048.1 and GB7251.1.

All equipment of the fully underground prefabricated substation is installed inside a fully sealed enclosure. The enclosure is internally divided into a high-voltage switchgear compartment, transformer compartment, and low-voltage switchgear compartment. Each compartment is equipped with lighting devices, and the switchgear is equipped with forced ventilation and temperature control devices, heating devices, and other equipment.
All the above equipment is installed below ground level. Its internal equipment is the same as that of a conventional above-ground prefabricated substation. The 10 kV input voltage is stepped down by the transformer to a 400/220 V distribution voltage and then supplied to the load points. The key technologies of this fully underground prefabricated substation are the enclosure's sealing performance, corrosion resistance, and pressure resistance.
Specifically:
1. From the bottom of the enclosure to the body, it must remain free from signs of corrosion for at least 50 years.
2. The enclosure must withstand the erosion caused by concrete and groundwater pressure while maintaining good structural integrity.
3. All sealing points, including equipment access openings, personnel entrances and exits, and cable entrances, must withstand the seepage pressure of groundwater, with no water seepage inside and no dampness or moisture inside the enclosure.
YBD1-12 fully underground prefabricated substation meets the above basic requirements and mainly provides the following three functions:
1. One end of the enclosure is equipped with two drainage troughs. During rainy weather, rainwater can quickly enter the drainage system through the drainage troughs without entering the interior of the prefabricated substation.
2. In addition to draining rainwater, the drainage trough also serves as the air inlet for the circulation ventilation system inside the enclosure. Air enters the enclosure through the air inlet to form circulation, maintaining a balanced temperature and humidity inside the enclosure and reducing the temperature rise of the transformer.
3. In the event of flooding that occurs once every 50 or 100 years, when rising groundwater causes the drainage system to backflow and the drainage trough can no longer drain water, the ventilation device will automatically shut down, isolating the interior and exterior of the enclosure. This prevents flooding from affecting the equipment and allows the prefabricated substation to continue operating.

At present, many substations in some cities are installed in high-rise basements. Once heavy flooding occurs, they are basically submerged, and most of the equipment is damaged after the water recedes. If fully underground prefabricated substations are used as power distribution equipment, equipment flooding can be avoided. Fully underground prefabricated substations also have the following advantages:
1. They can greatly save land resources, eliminating the need for land acquisition and reducing infrastructure investment.
2. There are no obstacles above ground, so they do not affect the environment or people's visual experience and landscape.
3. When installed in lawns or green belts, various decorative and landscaped elements can be designed above ground, such as sculptures and rockeries. Where there are requirements for large squares or road edges, and where no obstacles, including ventilation ducts, are allowed above ground, plaza-type prefabricated substations can be selected. The ventilation openings of this type of prefabricated substation can be completely concealed below ground level.
4. The power distribution equipment of the fully underground prefabricated substation is installed underground, providing high safety and reliability.
5. There is no noise impact from the transformer above ground.
6. As the underground environment is relatively cool, the temperature rise during transformer operation is more stable.
7. The internal space of the fully underground prefabricated substation is relatively spacious, and maintenance and operation will not interfere with the ground surface or cause any damage to the surrounding environment.