(1) induction heating method. Is the transformer body in the original tank, the fuel tank winding coil through the current, the use of the cortex of the heat to dry. At this time the wall temperature does not exceed 115 ℃ ~ 120 ℃, body temperature should not exceed 90 ℃ ~ 95 ℃. In order to facilitate the winding coil, as far as possible to make the coil less number of turns or smaller current, the general election current 150A, wire available 35 ~ 50mm2. The tank wall can pad a number of asbestos, wire wound on the asbestos strip. The power required for induction heating depends on the type of transformer and the drying conditions.
(2) hot air drying method. The transformer on the drying room, access to hot air drying. Drying room can be based on the size of the transformer body panels with panels covered with asbestos board or other impregnated fire solution canvas or asbestos linen. Drying room should be as small as possible, the distance between the wall and the transformer should not be greater than 200mm. Available electric furnace, steam serpentine to heat.
Electricity consumed by the electric furnace is calculated as follows: every minute through the drying chamber hot air Q, according to the drying chamber volume q to choose, generally calculated with Q = 15qm3.
P ≈ 0.07γQ (t2-t1) where P-electric furnace power required, kW γ-specific heat of air constant pressure (both 0.31) t2, t1-inlet hot air temperature and ambient temperature, ℃
Dry hot air inlet temperature should be gradually increased, the maximum temperature should not exceed 95 ℃, hot air inlet should be equipped with a filter or metal grid to eliminate Mars, dust. Hot air should not be blown directly to the body, blowing evenly from the underside of the body to the ministries, so that moisture through the box vents release.
(3) vacuum drying method. This drying method is based on the air as a heat carrier medium, under atmospheric pressure, the transformer body or winding gradually warm up to 105 ℃, began to vacuum for processing. As the heat transfer is slow, uneven heating inside and outside (cold heat), high voltage and large capacity of the transformer due to the thick insulation, often require more than 100h preheating, the production cycle is very long, and the drying is not complete, very Difficult to meet the transformer on the insulation requirements. But the equipment is simple, easy to operate.
(4) vapor phase vacuum drying method. This drying method uses a special kind of kerosene vapor as the heat carrier. The kerosene vapor introduced into the vacuum tank condenses on the transformer body and releases a large amount of thermal energy, thereby heating the drier body. As kerosene steam heat (kerosene heat of 306 × 103j / kg), so the transformer body dry heating more thoroughly, more uniform, high efficiency, and the insulation material damage is also very small. However, due to its complicated structure and high cost, it is currently limited to the application of large transformer drying treatment at 110kV and above.
