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The rainy season is approaching, hot and humid become an unavoidable problem in life, but also become an unavoidable problem in the distribution network, in order to ensure the safe and reliable operation of the power system, the dehumidification of electrical equipment has become a major problem that the power industry needs to deal with. To this end, this period of SEPRI brings you to focus on the specific measures of moisture and dehumidification of electrical equipment to ensure the safe and stable operation of power equipment in the rainy season.

Long-term damp affects the safe operation of electrical equipment

The main metal damage forms of electrical equipment are divided into corrosion, fatigue, friction, friction, etc., which have a great impact on the life of the equipment. Among them, the proportion of corrosion damage caused by moisture is large. China is close to or has reached the advanced level at home and abroad in the conventional electrical equipment loss prevention, has also accumulated rich experience in manufacturing and use of maintenance and has basically met the conventional environment and general conditions of use of electrical engineering applications. But the application of electrical equipment under special environmental conditions is far from enough.

In particular, the electrical equipment exposed to the outdoor environment for a long time should pay attention to the moisture and humidity of the rainy season. Outdoor 35 kV box type substation is a kind of high-voltage switchgear, distribution transformer and low-voltage distribution device organic combination, installed in the mobile steel structure box, is currently the city network construction and transformation of the widely used substation.

When the rainy season comes, when the high pressure chamber air is directly connected with the outside world, the outdoor high humidity air directly penetrates into the high pressure chamber, and the high pressure chamber is usually arranged on the first floor of the substation. After the surface moisture and cable trench moisture are collected, the high pressure chamber humidity is very large, which seriously affects the safe operation of electrical equipment. Therefore, it is very important to moisture-proof outdoor 35 kV box-type substation.

Safety problems caused by long-term damp in electrical equipment are common. There was a power supply company inspection personnel found a 35 kV high voltage room filled with smoke and burnt smell, 35 kV line protection trip. Then the professional and technical personnel were organized to conduct a comprehensive inspection of the equipment, and it was found that there were serious discharge phenomena in the switch spacing busbar and the wall bushing. After the test, the insulation of the 35 kV busbar together with the contact box of the trolley switch and the contact box current transformer to the ground decreased seriously, only 3~5 megohm, through the on-site equipment accident investigation and check the equipment operating records, the relevant professionals analyzed that the insulation breakdown was caused by long-term moisture caused by the internal deterioration of the insulation.

According to years of experience in electrical environment management, when the rainy season comes, the humidity of the high pressure chamber is as high as 95%. In a high humidity environment for a long time, it is easy to cause condensation, and condensation often causes electrical discharge in the high voltage cabinet, and even causes the switch cabinet to explode. In addition, the high voltage chamber electrical equipment for a long time in the high humidity and high temperature environment, it is easy to cause serious corrosion of various metal materials, resulting in switch cabinet refusal and affect the normal operation of the brake. If the moisture in the 35 kV substation is not solved in time, then the failure caused by moisture may occur at any time.

The effect of moisture proof measures in outdoor substation is remarkable

The factors affecting the corrosion of electrical equipment are more complex, with the different climate and regions, the surrounding air temperature, humidity, impurity composition and concentration are very different, and the degree of corrosion of electrical equipment is also different. Under normal circumstances, the impact of humidity on outdoor box substations focuses on the following major problems.

First of all, the cable room below the box has no ventilation facilities, and the surrounding walls and floor are not dry for a long time. The outer sealing around the bottom of the box is not perfect, and the wall of the box will seep water into the wall around the cable room from outside to inside in rainy days, causing the air at the bottom of the box to be humid. Second, because the outdoor surface of the box cable is surrounded by grass, rainwater is stored in the soil and gradually seeps into the indoor wall of the cable. The bottom around the box of the high voltage switch cabinet and the cable room are not fully sealed, and there is air flow collusion between the box and the cable room. Third, the installation position of the top exhaust fan in the box is unreasonable. Whenever the exhaust fan is opened, the wet air in the cable room will flow into the box, and the cold moisture will form water droplets when flowing through the electrical equipment and adhere to the surface of the insulated part of the electrical equipment. Fourth, there is only a small heating plate in the cable outlet space of the switch cabinet, and the temperature and humidity controller is installed in front of the cabinet, which fails to truly reflect the temperature and humidity value of the high-pressure equipment space in the cabinet.
In response to the above specific problems, Juhang Electrical through a large number of field investigations, comprehensive field conditions of various electrical equipment environment, tailor-made for power enterprises to create a series of effective dehumidification solutions to solve the problem of electrical environment moisture. The electric environment control and monitoring system of Juhang Electrical uses big data technology to effectively put forward hidden danger warning, fault display and automatic handling of minor accidents in the electrical environment, providing important guarantee for the safe operation of electrical equipment.

Reasonable moisture-proof measures in substation can avoid the impact of moisture on electrical equipment. According to different environmental conditions, rectification measures should be taken to remove moisture from the cable room, seal and isolate the box from the cable room, keep the space inside the box and the switch cabinet dry, and specifically improve moisture-proof measures. In addition, through technical means, the continuous upgrading of electrical equipment series dehumidification products has become the future trend of avoiding electrical equipment moisture. The SEPRI-CS-NL anti-condensation device of SEPRI series dehumidification products can realize the functions of high humidity early warning, fault alarm, temperature compensation and fault alarm output. SEPRI-CS-DZ overhead dehumidification system meets the dual-cycle system design, faster and stronger dehumidification speed; Solve the dehumidification problem of bus bridge and bus room; Original ultrasonic water atomization isolation discharge method, split type design, prevent external debris into the cabinet. It further guarantees the safe operation of electrical equipment in rainy season.

In addition, according to the impact of the rainy season on the box-type substation, besides the installation of reasonable dehumidification and dew prevention products, the substation operation management personnel also need to strengthen the comprehensive moisture-proof specification work. Before the rainy season, the substation operator should take waterproof, moisture-proof and sealing measures on the cable trench and the holes of the switch cabinet in time, ensure the internal and external insulation of the cable trench of the substation high voltage room, and prevent the cable trench moisture from directly invading the high voltage switchgear.

With the development of intelligent substation, in the operation process of intelligent substation, the dehumidification automation is also increased requirements, Juhang Electrical keeps pace with The Times, and designs a system scheme that is more suitable for the overall monitoring and management of substation dehumidification. At present, the overall management system of the operation environment of Juhang Electrical equipment has been widely used in the substations of power grid company and China Southern Power Grid Company. After the rectification of moisture-proof measures in the substation during the rainy season, the moisture of the equipment has been greatly improved, which provides an important guarantee for the safe operation of the electrical equipment.