Classification and characteristics of dry-type transformers:
Dry transformer is the most widely used type of disaster prevention transformer. At present, the manufacturing technology is mature, and many factories at home and abroad can produce in large quantities. The annual production volume of dry-type transformers of the factory with the largest domestic and foreign output has exceeded 3,000MVA (foreign) and 2,000MVA (domestic) respectively. It is suitable for environments with high pollution, high temperature, and humidity. It has the advantages of flame retardant, flame retardant, pollution-free, and maintenance-free, so it is used in large quantities. At present, the highest voltage level of dry-type transformers has reached 35kV, and the maximum capacity is 20MVA.
Classification of dry-type transformers:
Impregnated dry type transformer
This type of transformer has the longest production history and its manufacturing process is relatively simple. The wires are wrapped with glass fiber, and the pads are hot-pressed with corresponding insulation grade materials. Depending on the impregnating paint, the insulation grade of the transformer is divided into B, F, H and C levels. All the air channels of the main longitudinal insulation use air as the insulating material. Since this type of transformer is more affected by the external environment than resin, its output tends to decrease both at home and abroad.
Resin dry type transformer
Resin dry-type transformers are divided into four structures: resin plus filler casting, resin casting, resin wrapping, and resin vacuum pressure impregnation. Although the equipment used has a large investment, the installation and maintenance costs are low.
Resin casting and resin plus filler casting structures
The two structures are basically the same. The low-voltage winding is wound with foil (copper or aluminum) or wire (impregnated with paint and end-sealed), and the high-voltage winding is wound with foil strips (copper or aluminum) on an epoxy glass cylinder in segments. (8 to 12 segments), or use flat or round wire to wind into segmented cylinders, and then put them into the casting mold.
Resin wrapping structure
The low-voltage winding structure is the same as the previous one. High-voltage winding is performed on a winding machine, and the inner mold is an epoxy fiberglass cloth cylinder. The advantage of this structure is that no casting mold is required. It takes 8 hours to wind a high-voltage winding with this structure, which is roughly the same time as it takes to wind a segmented cylindrical structure of a cast high-voltage winding, while it only takes 2 hours to wind a high-voltage foil winding. At present, the cost of this type of product in China is about 1.25 times that of resin plus filler products.
Resin vacuum pressure impregnated structure
The low voltage winding structure is the same as above. After the high-voltage winding is wound on the winding machine and pre-pressed and pre-dried, it is placed in a pouring tank for vacuum treatment. The resin is injected under vacuum to penetrate into the conductor, and the entire winding is wrapped in resin. Then the vacuum is released and pressure is applied to allow the resin to penetrate into the winding well, and then the winding is sent to the furnace for processing.
The advantage of this process structure is that it does not require a casting mold. The winding is the same as the previous ones, except that it requires vacuum pressure impregnation. This is a new technology developed in recent years and is similar to foreign vacuum pressure impregnated casings (replacing tape, The products developed at the same time as oil-paper casing) should be promising, but they have not been developed in China so far.
Characteristics of cast resin dry-type transformers
1. Oil-free, pollution-free, flame-retardant, self-extinguishing and fire-proof.
2. High insulation temperature rise level: Class F insulation, the temperature rise of the transformer can reach 100K.
3. Low loss and high efficiency: SC(B)9 series loss is 10% lower than the current new national standard (GB/T10228).
4. Low noise: SC(B)9 series distribution transformers can usually be controlled below 50dB.
5. The partial discharge is small (usually less than 10PC) and has high reliability, ensuring long-term safe operation and a lifespan of 30 years.
6. Resistant to cracks, temperature changes, high mechanical strength, and strong resistance to sudden short circuits.
7. It has good moisture-proof performance and can operate normally under 100% humidity. It can be put into operation without drying after shutdown.
8. Small size and light weight. According to relevant statistics, the external dimensions of oil transformers are more than twice that of dry transformers.
9. There is no need for a separate transformer room, core maintenance and load-bearing beams, which saves land and space for civil construction; because it is oil-free, no toxic gases will be produced and no pollution will be caused to the environment. No ancillary buildings such as oil collection pits are required. , reducing civil construction costs.
10. It is easy to install, requires no debugging, and requires almost no maintenance; no need to replace or check oil, and low operation and maintenance costs.
11. Equipped with a complete temperature protection control system to provide reliable guarantee for the safe operation of the transformer. From the comparison of comprehensive technical and economic performance such as low noise, energy saving, fire prevention, saving civil construction costs, operation and maintenance management fees, and a life span of up to 30 years, dry-type transformers show their obvious advantages.
