Transformer Drying Treatment
Transformer is an inevitable power equipment in the power system. It plays a very important role in the power system and is the core of the substation. In the case of transformer insulation damp, transformer winding replacement or insulation, the transformer needs to be dried. Do you know the following treatment methods?
1. Copper loss drying method of winding: generating heat by transformer winding itself, heating winding insulation, small workload, fast temperature rise, saving time. The disadvantage is that the power supply capacity is large.
2. Vacuum drying method of oil tank iron loss: vacuum drying by transformer oil tank itself requires small power supply capacity and low voltage. The disadvantage is that the workload is large and the drying time is long, which requires a lot of materials, equipment and calculation and analysis.
3. Hot air drying method: Put transformer in drying chamber and pass hot air into drying chamber for drying treatment. The drying chamber can be assembled according to the size of the transformer, and the walls are covered with asbestos board or other canvas or asbestos linen impregnated with fire-proof solution.
4. Zero Sequence Current Drying Method: Use transformer winding to electrify to heat oil tank, iron core and winding. The disadvantage is that before and after drying the transformer, it needs to discharge oil, hang core and change the winding connection mode. The workload is large and the temperature is not well controlled, which may cause local overheating.
5. Zero-sequence short-circuit drying method: This method is a comprehensive method between zero-sequence current drying method and winding copper loss drying method. The former is heated by iron loss, the latter is heated by copper loss, and the zero-sequence short-circuit drying method is a combination of two methods for drying treatment.
6. Induction heating method: the transformer body is placed in the original tank, winding the tank with coils, and drying by eddy current heating of the tank skin. The temperature of the box wall is controlled below 115℃~120℃, and the temperature of the body is not more than 90℃~95℃.
7. Vacuum drying method: With air as heat carrier, the transformer body or winding is gradually preheated to about 105 C, and vacuum treatment is started. This method has the advantages of simple equipment, convenient operation, slow heat transfer, long production cycle and incomplete drying. It is difficult to meet the insulation requirements of transformers.
8. Gas-phase vacuum drying method: This method uses a special kerosene vapor as the heat carrier, and the kerosene vapor introduced into the vacuum tank condenses in the transformer body to release a large amount of heat energy, thereby heating the dryer body. The advantages of this method are large heat energy, more uniform and thorough drying, high efficiency and less damage to insulating materials. The disadvantage is high cost and complex structure. At present, the drying treatment of large transformer body is limited to more than 110 kv.
No matter which method is used, the temperature of transformer body should not exceed 95℃ in oil-free drying and 80℃ in oil-carrying condition to prevent oil aging.