In addition to affecting the health of the staff, the wet environment of the underground space will also cause corrosion damage to the electrical equipment in the project. Humidity is an inherent characteristic of the underground space, and the thermal and humid environment of the underground project has a great impact on the reliability of the electrical equipment. Due to the increasingly high requirements for the internal environment of modern underground engineering, especially into the information age, computer control technology and intelligent management technology have been introduced into the control and management of the internal equipment of underground engineering, and the technical content of the internal equipment is getting higher and higher, so that the internal equipment and system themselves have higher and higher requirements for the internal environment, and the quality of the internal environment of underground engineering has become a problem The basic guarantee of reliable operation of internal equipment and systems.
For the electrical equipment used in high humidity environment, at present, the components themselves are used for moisture-proof treatment at home and abroad to improve the protective performance of components. However, the use of wet and thermal components of the product cost is high, so in addition to special applications such as ships, almost all use ordinary switching devices, the equipment is more concentrated distribution box for the overall moisture, such as resistance wire heating and drying methods to reduce the internal relative humidity of the distribution box box, but this moisture-proof method when the equipment stops running, the relative humidity inside the box increases again, strict Heavy will cause moisture condensation, accelerate the corrosion of electrical equipment. Therefore, it is of great significance and practical value to study the moisture resistance of electrical distribution box in underground engineering.
First, electrical distribution box box sealing technology
The box of the electrical distribution box is generally sealed with gaskets or sealing strips. When the door is closed to produce a certain pressure on the box, the gasket or seal strip is compressed under the action of external force and a certain deformation can make up for the uneven surface of the box component and the gasket or seal strip, so as to achieve the effect of sealing protection.
Research on moisture-proof technology of distribution box in underground space
Second, the selection and placement of desiccant in the electrical distribution box
The sealing of the distribution box can ensure that the humid air outside the box does not penetrate into the box, but the opening and closing of the distribution box will allow the outside humid air to enter the box. If not treated, the humid air in the box will not be able to discharge the distribution box, and the long-term humid environment will cause the electrical equipment in the box to be damaged and formed a hazard. Therefore, when sealing the electrical distribution box, it is also necessary to consider drying the humid air in the box, and the usual method is to place a desiccant in the distribution box. The selection of desiccant is as follows:
According to the form of reaction, desiccant can be divided into physical adsorption type and chemical adsorption type.
Physical adsorption desiccant is the use of material porosity for the absorption of water vapor, even if the absorption of water reached saturation state, there will be no deliquescence and shape change, renewable use, such as silica gel desiccant, clay desiccant and so on.
Chemisorbed desiccant is the use of chemical reaction or deliquescence absorption of water, rapid absorption of heat phenomenon, non-renewable use, such as lime desiccant, salt desiccant and so on.
Third, the internal and external pressure difference protection design of sealed electrical distribution box during intermittent work
For the electrical distribution box in the intermittent operation of underground engineering, before and after each operation, due to the thermal expansion and cold contraction of the air in the distribution box, a large pressure difference will be formed inside and outside the box, if not treated, it will affect the overall protective performance of the box and accelerate the damage of the seal. In order to avoid this situation, a device (such as a transformer breathing apparatus) can be set up in the distribution box to prevent the direct flow of internal and external air to eliminate the pressure difference between the inside and outside the box caused by the thermal expansion and cold contraction of the air.
Most of the electrical equipment used in the existing underground engineering in high humid environment adopts conventional ground general equipment, and there are very few special moisture-proof electrical products. Therefore, according to the internal environment of underground space, it has become urgent to study the sealing and moisture-proof technology of electrical distribution box and develop corresponding products. In particular, the study of passive moisture-proof technology has important practical significance for the development and utilization of underground space.