在湿热环境中干式空心电抗器容易发生由匝间短路引起的起火燃烧事故，目前的研究表明水分入侵是导致匝间绝缘失效的主要原因，但是对于具体的进水过程以及设备在湿热环境中的老化特性并不明确。因此本文首先研究环氧树脂的湿热老化特性，分析环氧树脂老化与设备失效之间的关系，接着研究包封在热应力作用下的开裂机理和裂纹检测手段，最后研究干式空心电抗器在湿热环境中的老化特性。首先配置了各种溶液研究溶质和温度对环氧树脂吸水、脱水、透水特性的影响以及在此过程中的老化特性。实验结果表明环氧树脂的吸水过程可以用郎缪模型描述，水势差和温度是影响吸水率的主要因素，而与溶质种类无关；环氧树脂吸水后在干燥环境中可脱去吸收的大部分水分，在不同溶液中的透水量也相差不大；吸水老化后环氧树脂表面出现直径在0.2 ~30 间的微孔，吸水率越大微孔数量越多，吸收电流也会随着含水率的增加而增大，吸水时主要发生了酯基的水解，活化能在老化过程中不断减小；环氧树脂虽然发生了不同程度的老化，但仍然具有较好的密封性，说明环氧树脂老化并不是导致干式空心电抗器失效的主要原因。接着通过仿真和实验研究了当温度变化时包封在热应力作用下的开裂情况，仿真结果表明当温度从25℃到100℃之间变化时，包封整体会受到水平向右的拉应力，聚酯薄膜和玻璃纤维与环氧树脂的交界面容易开裂，冷热循环实验结果也表明随着循环次数的增加，聚酯薄膜与环氧树脂界面、环氧树脂内部、包封外绝缘区域会依次出现微裂纹。本文也通过荧光渗透结合图像识别检测了包封裂纹缺陷，并定量给出裂纹周长、面积等特征量；最后研究了正常电抗器与缺陷电抗器在不同湿热老化条件下的老化特性与区别，实验结果表明紫外不是导致电抗器失效的原因，实验电抗器在水煮老化48 h后会发生RTV脱落、表面出现孔洞甚至鼓包等老化现象，但都能通过匝间绝缘测试，冷热循环水煮老化后电抗器老化现象更明显，电阻电抗变化更大，正常电抗器与缺陷电抗器的老化区别也更为显著，存在缺陷的电抗器会出现开裂现象，但所有电抗器都能承受10次以上的脉冲过电压测试。
Dry-type air-core reactors are prone to ignition and combustion accidents caused by inter turn short circuits in hygrothermal environments. Although current research shows that water infiltrating the package is the main cause of inter-turn short-circuit failure, the specific water infiltration process and aging characteristics of equipment in the hygrothermal environments are not clear. Therefore, it firstly studied the hygrothermal aging characteristics of epoxy resin, and analyzed the relationship between epoxy aging and inter-turn short-circuit failure. Then the cracking mechanism under thermal stress and crack detection method of the package are studied. Finally, the aging characteristics of dry-type air-core reactor in the hygrothermal environment are studied.Firstly, various aqueous solutions were dispened to study the influence of kind of aqueous solutions and temperature on the water absorptivity, dehydration properties and water permeability of epoxy resin, as well as the hygrothermal aging characteristics in this process. The experimental results indicated that the water absorption process of epoxy resin can be described by the Langmuir model. The water potential difference and temperature are the main factors affecting the water absorption, but have nothing to do with the kind of solute. After absorbing water, epoxy resin can remove most of the absorbed water in dry environment, and the water permeability in different aqueous solutions is not different. Micropores with a diameter between 0.2 and 30 appeared on the surface of epoxy resin after aging. The larger the water absorption rate, the more the number of micropores, and the absorption current will increase with the increase of water absorption. During water absorption, the hydrolysis of ester group mainly occurs, and the activation energy decreases continuously in the aging process. Although the epoxy resin has deteriorated to different degrees, it still has good sealing performance, indicating that hygrothermal aging of epoxy resin is not the main reason for a large amount of water penetration in dry-type air-core reactors.Then, the cracking of the package under thermal stress is studied by simulation and experiment when the temperature changes. The simulation results show that when the temperature changes from 25℃ to 100℃, the package is subjected to horizontal thermal stress to the right, and the interface between PET film and glass fiber and epoxy resin is easy to crack. Alternating cold and hot experiment also show that with the increase of cycle times, Cracks appeared in the interface between PET film and epoxy resin, inside epoxy resin and outside insulation area successively. In this paper, fluorescence penetration combined with image recognition is used to detect the package crack, and the characteristic parameters such as the perimeter and area of the crack are given qualitatively.Finally, the aging characteristics and differences between normal reactors and defective reactors under the different types of hygrothermal environment were studied. The experiment results show that ultraviolet is not the cause of dry-type air-core reactor failure. The test reactor can pass the inter-turn insulation test despite RTV loss, surface holes and even bursting after 48h of boiling experiment. The aging phenomenon of alternating hot and cold boiling experiment is more significant compared to boiling experiment, with a greater change in reactance and resistance. The aging difference between normal reactors and defective reactors is also more significant. Defective reactors may experience cracking, normal reactors and defective reactors can be distinguished by alternating hot and cold boiling experiment.
