In addition to the influence on the physical health of the staff, the wet environment of the underground space will also cause corrosion damage to the electrical equipment in the project. Moisture is an inherent characteristic of the underground space. The thermal and humid environment of the underground works has a great influence on the reliability of the electrical equipment. . As modern underground engineering demands more and more internal environment, especially in the information age, computer control technology and intelligent management technology have introduced the control and management of underground engineering internal equipment, and the technical content of internal equipment has become higher and higher. Internal equipment and systems themselves have increasingly higher demands on the internal environment. The internal environment of underground projects has become a basic guarantee for the reliable operation of internal equipment and systems.
For electrical equipment used in high-humidity environments, it is currently used at home and abroad to conduct moisture-proof treatment on the components themselves to improve the protective performance of the components. However, due to the high cost of adopting damp heat components, except for special applications such as ships, almost all ordinary switch devices are used, and the overall distribution box with more concentrated equipment is protected from moisture, such as resistance wire heating and drying. The relative humidity inside the distribution box is reduced. However, when the equipment stops operating, the relative humidity inside the box increases again. This will cause condensation and accelerate the corrosion of electrical equipment. Therefore, it is of great significance and practical value to study the moisture-proof problem of electrical distribution boxes in underground engineering.
First, the electrical distribution box sealing technology
The box of the electrical distribution box is generally sealed or sealed with a seal. When the box door closes tightly to the box body, the sealing gasket or the sealing strip is in a compressed state under the action of the external force and undergoes a certain deformation, which can make up for the unevenness of the box body member and the sealing gasket or the sealing strip surface. In order to achieve the effect of sealing protection.
Research on moisture-proof technology of underground space distribution box
Second, the use of desiccant in the electrical distribution box and placement technology
Sealing the distribution box can ensure that the humid air outside the box does not penetrate into the box, but the operation of the switch door of the distribution box will allow external humid air to enter the box. Without treatment, the humid air inside the box will not be able to drain out of the distribution box. Long-term wet conditions will cause damage to the electrical equipment in the box. Therefore, while sealing the electrical distribution box, it is also necessary to consider the drying and moisture absorption of the humid air inside the box. The usual method is to place a desiccant in the distribution box. The selection of desiccants is as follows:
According to the form of the reaction, the desiccant can be classified into a physical adsorption type and a chemical adsorption type.
Physisorption desiccant absorbs water vapor by the porous nature of the material. Even if moisture is absorbed into the saturated state, it will not undergo deliquescence and morphological changes. It can be used for regeneration, such as silica gel desiccant and clay desiccant.
Chemical adsorption desiccants absorb moisture by chemical reaction or deliquescence. When they are rapidly absorbed, they will be heated and non-renewable, such as lime desiccants and salt desiccants.
III. Design of pressure difference protection inside and outside sealed electrical distribution box during intermittent work
For electrical distribution boxes that run intermittently in underground engineering, before and after each operation, due to the thermal expansion and contraction of the air in the distribution box, a large pressure difference will form inside and outside the box. If no treatment is performed, it will affect the box. The overall protection performance accelerates damage to the seals. To avoid this situation, a device (such as a transformer respirator) that prevents the passage of air from inside and outside can be installed in the distribution box to eliminate the pressure difference between the inside and outside of the box caused by the thermal expansion and contraction of air.
Most of the electrical equipment used in the existing underground engineering in the high-humidity environment uses conventional ground general-purpose equipment, and special moisture-proof electrical products are very few. Therefore, for the internal environment of the underground space, it is urgent to study the sealing moisture-proof technology of the electrical distribution box and develop and develop the corresponding products. In particular, passive moisture-proof technology research has important practical significance for the development and utilization of underground space.
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