Analysis on moisture and dehumidification of high voltage distribution box and its treatment

1. Reason analysis of insulation performance decline of voltage switch cabinet

1.1 process of insulation performance degradation of high voltage switchgear

During the use of high-voltage switchgear in high-voltage distribution room, due to environmental and climatic factors, the insulating materials in high-voltage switchgear are eroded by ozone, weak acid corrosive gas and crystal water for a long time, and the insulation strength will be significantly reduced. This is because when a small amount of water vapor enters the cabinet, ozone is easily formed due to the strong electromagnetic field. Ozone has a strong destructive effect on epoxy resin, resulting in the decline of insulation. In addition, after the water vapor enters the cabinet, it is easy to condense into water droplets, and the water droplets and dust will adhere to the surface of the insulating material, which will aggravate the damage to the insulation ability for a long time, resulting in the short circuit between phases of electrical equipment, causing huge losses.

1.2 reasons for the decline of insulation performance of high voltage switchgear

For the insulation performance of electrical equipment, two factors are humidity and temperature. Cypress found that condensation is not serious in the long-term humid environment. On the contrary, in the areas with frequent alternation of humidity and dryness, condensation is a serious disaster area in the switch cabinet. Therefore, cypress concluded that the temperature and humidity difference is that the temperature of the environment where the high-voltage switchgear is located fluctuates greatly, and some hygroscopic dust will cause water vapor condensation. Especially under the condition of changing power load, there will be a large range of temperature difference inside the high-voltage switchgear. If the relative humidity of the switchgear is too high, it is easy to form water film on the surface of electrical equipment inside the switchgear, and the corrosion rate of metal under the action of water film will be greatly accelerated. In addition, the distribution room, cable trench and other external environment will also have a great impact on the normal operation of high-voltage switchgear. For example, if the cable trench is not sealed tightly and there is long-term ponding, a large amount of moisture will be generated. Once the moisture enters the distribution room, the relative humidity of the distribution room will be greatly increased, which will affect the normal operation of the high-voltage switchgear.

2. Moisture proof and dehumidification of high voltage distribution room and its treatment

2.1 installation of switch cabinet heater

The high voltage switch cabinet is equipped with a switch cabinet heater to heat the switch cabinet, so that the temperature inside the switch cabinet is always higher than the ambient temperature outside the switch cabinet, which can improve the condensation point of water droplets and effectively prevent condensation. The internal temperature of the switch cabinet is always at least 2 ~ 3 ℃ higher than the external temperature of the switch cabinet, so as to eliminate the condensation condition inside the switch cabinet. This method is more convenient to install, but the disadvantage is that although it can prevent condensation, it can not get out the moisture in the cabinet. As long as it stops working, it is easier to form condensation. Secondly, the high-voltage switch cabinet itself will heat up in the working process, and the heater will cause the temperature in the switch cabinet to be higher than the normal working temperature.

2.2 install moisture absorbent in switch cabinet

In the actual application, because of its limited water absorption, when it reaches a certain saturation, it stops absorbing moisture, and the absorbed water is difficult to discharge, so it needs to be replaced in time, and the maintenance workload increases. In addition, it is not suitable for high voltage switch cabinet which is especially humid and large. Only suitable for small distribution box, such as meter box.