Various dry type transformer models feature inventory

1. Introduction of SF6 gas insulated dry type transformer and dry type transformer:

SF6 transformers are widely used in Japan, but few in China. It is the most outstanding superiority application area of ​​its dry type transformer. The transformer capacity can be three-phase 300MVA, the voltage can be single-phase 500kV (all made in Japan), and it can also manufacture 10kV-class power distribution. Transformer (In early 1988, China's Guangzhou High Voltage Electrical Appliance Factory, Beijing Second Transformer, Changzhou Transformer Factory were developed, and Beijing Erchang was once produced in small batches). Its structural design and manufacturing process have many similarities with traditional oil-immersed transformers. Transformer manufacturers can research and develop it without much equipment investment. Of course, its defects are also obvious. When the SF6 gas metal is overheated, it will be decomposed into a kind of SF4 extremely toxic substance. In addition, the manufacturing process is not good, and the consequences of the leakage to the atmosphere will be unimaginable. Many domestic experts believe that China should not develop such transformers when the manufacturing process is not up to standard.

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2. Introduction of epoxy resin vacuum casting transformer and dry type transformer:

(1) In the early 1970s, Shanghai and Beijing Transformer Factory successively developed thick-insulated quartz powder filler vacuum-cast epoxy resin-encapsulated dry-type transformers. Since then, dry-type transformers have officially become a batch supply of new-generation products, even though it was on the material. There are some problems in the manufacturing process and it was replaced by the thin epoxy resin insulation technology. However, it has created a good start for dry-type transformers and promoted the development of dry-type transformer technology in China.

(2) Thick insulation (6mm) is difficult to solve the cracking problem. When people are suspicious of epoxy dry-type transformer technology, Shunde Transformer Factory successfully introduced pure epoxy resin (1-3mm) technology without quartz filler from Germany. It emerged to make China's dry-type transformer technology develop rapidly. The quality of this technology product is relatively stable (using imported pouring equipment and imported resin), users are satisfied. Coupled with the good economic benefits of the manufacturing plant at the time, everyone has launched. More than 10 started, 30 later, 70, and more than 100 use this technology. At present, it has accounted for 90-95% of the dry-changing market, and its production capacity has exceeded 30 million kVA per year. The supply is already much better than the demand. This kind of transformer is already familiar to everyone, we will not say more.

(3) At the beginning of this century, Shanghai GE Company developed a H-class insulating tape-filled thin insulating epoxy vacuum-transferred dry-type transformer using American technology research. The internal insulation of the transformer is made of NOMEX® insulation paper. He successfully solved the technical problems of insulation coordination, process formulation and uniform casting between various insulating members inside the transformer. It appears that the insulation resistance of the epoxy-encapsulated dry-type transformer is improved from B-class and F-class to H-class. To improve to C-class, the current technology is impossible.

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3, epoxy resin winding process dry type transformer and dry type transformer model introduction:

(1) Shanghai ABB manufactures a dry-type transformer called "Raytheon" technology, which is also a distinctive product. It does not require expensive pouring equipment and a variety of casting molds, product derivation and production is very convenient. The pre-impregnated glass fiber is tightly wrapped and cured at a high temperature to make the transformer mechanical strength particularly good.

(2) Of course, it is difficult to put the board, the main longitudinal insulation field strength should be selected according to the absence of partial discharge, so the transformer volume may be larger. Relative to manufacturing costs. In addition, the appearance of the coil is not as smooth as the mold cast product. This kind of product is rare in China or abroad.

The use of epoxy resin as the main insulation product is very common in China and has been accepted by many users. Recently, many experts pointed out that the final degradation treatment of dry-type transformers and environmental protection issues should be taken seriously.

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4, using NOMEX? paper insulation specification dry type transformer and dry type transformer model introduction:

4.1 We understand the performance of NOMEX® paper and we can clearly understand the characteristics of this transformer.

(1) NOMEX® insulation paper is composed of an aromatic polyamide polymer fiber.

This fiber woven fabric is an acid-resistant, alkali-resistant, fire-resistant fire service or space suit. We can see from its molecular structure that it has no weak CH bond, and its molecular structure cannot be destroyed by external high temperature. It can only break bonds between molecules, and its chemical properties are particularly stable. It is not affected by insects, fungi and mold. It has good compatibility with oil, impregnating varnish, fluorocarbon and so on.

(2) NOMEX? Insulation paper electrical performance is very prominent, can be summarized as follows:

l High surface resistivity (1013 ?/cm2 and volume resistivity (1011 ?/cm3) at 250 °C;

l In a wide frequency range, the dielectric loss is always 0.01 at 200 ° C and below;

l Its relative dielectric constant is 1.5-2.5, which is lower than many common insulating materials;

l Its power frequency breakdown voltage reaches 35kV/mm, and the initial voltage of creeping discharge is very high.

(3) NOMEX? Insulation paper has good mechanical properties:

High temperature and high pressure treated NOMEX? Insulation paper has almost constant elongation. It has high tear strength and good wear resistance and toughness. It has good high temperature mechanical properties and good low temperature mechanical properties.

(4) NOMEX? Insulation paper has the highest temperature resistance grade, C grade, and can work safely at 220 °C for a long time. Short-term operation at 350 ° C, no softening, melting and combustion support at 250 ° C. No toxic or corrosive gases are released at 750 ° C and embrittle at very low temperatures. It maintains stable performance over a wide temperature range. It is used in the United States for Class C insulation products.

(5) It has excellent moisture resistance:

At a relative humidity of 95%, the dense NOMEX® insulation paper maintains a dielectric strength of 90% when completely dry. It is difficult for water to penetrate the surface treated with high temperature and high pressure.

(6) The most outstanding performance of NOMEX? insulating paper is that its flame retardancy is particularly good. It has been proved by experiments that its LOI of 250 °C is still greater than 20.8%, it will not support combustion and can be flame retardant.

Oxygen limit index (LOI) (%)

(7) NOMEX? Insulation paper is safe. DuPont is a chemical company with a long history in the world (today, 200 years old), and he has a strong sense of safety and environmental protection. His product, NOMEX? Insulation paper is also a product, it will not release harmful substances when it is burned. This is verified by the F1 fire resistance test of the Italian CESI independent laboratory produced by Yunnan Transformer Factory.

(8) It can be seen from the NOMEX® insulation paper aging test that the dielectric strength, tensile strength and elongation are still in good condition under the action of 100 °C high temperature of 100,000 hours, and it is UL certified in the United States.

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4.2 DuPont? ReliatraN? technology "OVDT" open dry type transformer and dry type transformer model introduction:

Jiangsu Yangzhong Zhongdian Equipment Manufacturing Co., Ltd. developed the "OVDT" open type dry-type transformer by adopting the DuPont ReliatraN? technology transformer specification. In 2000, the SG10 type 10kV grade 30-2500kVA was appraised and officially introduced to the market. And become the DuPont? ReliatraN? technology transformer licensed manufacturing plant.

The low voltage of the transformer is a foil type or a plurality of spiral coils, and the high voltage is a cake coil. High-density NOMEX® paper is used for the daytime, inter-layer, inter-cake pads and stays. The coil is subjected to multiple vacuum and pressure (VPI) immersion treatments. The process methods can be divided into two types. One is to process only the coil, the size of the impregnation tank can be smaller, and the appearance of the transformer is relatively neat. Another method is to assemble the transformer. After the test is passed, the whole transformer is immersed. At this time, the transformer is completely encapsulated by the impregnating varnish, and the encapsulation effect is better. Here we introduce the former method. This process is roughly like this:

l Preheating: first arrange the coil, test it, then put it into the drying room, bake at a certain temperature and time, take out the coil, and the surface temperature drops to 100 °C;

l Vacuum: Place the coil into the VPI dip tank and evacuate to < 5mm Hg for a period of time;

l Impregnation: open the VPI impregnation tank release valve, put the impregnating varnish; to the top of the coil more than 50mm;

l Vacuum: vacuum again for a period of time;

l Pressurization: After releasing the vacuum, add 6 bar pressure for a longer period of time;

l Drip dry: After releasing the pressure, take out the coil and drain the paint as much as possible;

l Drying: Put the coil into the drying room and dry it;

l Cooling: Take out the coil and cool it for installation.

The appearance of this type of transformer does not seem to differ much from the previous Class B insulated open-type dry-type transformers. In fact, it is two completely different products. The insulating material is high-performance NOMEX® insulating paper, while the B-class insulating insulating material is made of glass fiber and epoxy. The current manufacturing process is vacuum pressure impregnation, while the B-class insulation is impregnated at normal temperature and pressure. In addition, the insulating paint for VPI impregnation is a non-combustible resin. Vacuum, especially 6 bar high pressure, infiltrates the H or C insulation paint into each gap and fills it up. After heating and curing, the coil conductor and the insulation are completely encapsulated. After this process, the coil has strong moisture and dirt resistance. The author believes that open-type dry-type transformers use vacuum pressure (VPI) impregnation is better than vacuum (VI) only, which we also confirmed from the US EPOXYLITE company.

This open type "OVDT" transformer coil has more heat dissipation surface than the encapsulated "VDT". In addition to the load loss limit, the transformer operating temperature has a large margin. In this way, the user can have two advantages: 1 high operational reliability; 2 super nameplate running ability, this transformer can still overload 1.2 times without safe operation.

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4.3, DuPont? ReliatraN? Technology "VDT" encapsulated dry-type transformer and dry-type transformer model introduction:

The DuPont? ReliatranN? Technology Transformer Licensed Factory--Kunming SEG Mai Special Transformer Electric Co., Ltd. (a subsidiary of Yunnan Transformer Electric Co., Ltd.) introduced a dry-type transformer originally called SECURAMID? technology from France. This technology is based on the UL approved NOMEX® aramid paper high-voltage dry-type transformer HV-1 insulation specification. The two parts of this insulation specification, namely the insulation structure and the insulation system, have the same insulation structure between the SECURAMID® technical specification and the NOMEX® aramid paper HV-1 insulation specification. The insulation system differs from the highest operating voltage of the former. Um is 11.5 kV; impulse voltage BIL is 75 kV, while latter Um is 15 kV; BIL is 95 kV. Now in the DuPont? Reliatran? transformer technology category. This kind of transformer design is very special. Its calculation of heat and force in electric, magnetic, thermal and force calculations is different and the precision is higher. The structure design is also very elegant. It uses NOMEX® insulation paper as the insulation foil coil for low voltage and NOMEX® insulation paper for insulation segmentation layer coil. The entire coil is encapsulated with high performance NOMEX® paper and Class H flame retardant, moisture and dirt resistant insulation resins. Coated NOMEX® paper and conductors are polymerized at high temperatures to form a solid body. NOMEX paper has a very low dielectric constant and a high dielectric strength and moisture and dirt resistance. This transformer has outstanding performance. At present, the domestic dry-type transformers also have three special tests in accordance with the European standard HD464, F1 fire resistance, E2 environmental adaptability and C2 thermal shock resistance. These three special tests have been included in the 2000 version of the IEC60076.11 international standard and will be included in China's dry-type transformer standards in the near future. These three special test dry transformers are very meaningful. The raw materials of this kind of transformer are basically imported, and the high-quality products will make the price slightly higher than the ordinary transformer, but it is definitely worth the money.

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4.4. These two DuPont? ReliatraN? technology transformers have their own characteristics, as well as common features:

(1) High reliability, high temperature resistance, and high heat tolerance:

NOMEX? Paper is a Class C insulation, which can operate safely at a high temperature of 220 °C for a long time. The transformer is designed with H-class insulation and the maximum operating temperature is 180 °C. The use of NOMEX® paper has a great heat tolerance. Especially in the lower room, poor ventilation and small space, the use of this transformer has great advantages. NOMEX® paper has high electrical strength and high surface and volume resistance at 250°C. Even more, it has a smaller dielectric constant. This is an air-based dry-type transformer, which is extremely extreme. The dielectric constant of NOMEX® paper is usually 1.5 to 2.5, which is very close to the dielectric constant 1 of air. In the structural design, the insulating material with lower dielectric constant is used, so that the electric field distribution of the whole transformer is relatively uniform, and the inside of the winding contains a small amount of air bubbles, which will not cause harm to the product. The transformer board is smaller. , high dielectric strength under insulation dimensions.

(2) Good safety, NOMEX? Paper Oxygen Index (LOI) is high:

The material's oxygen limited index is related to the material's own characteristics and the temperature at which it is placed. The same material, the higher its temperature, the smaller the oxygen-limited index, it is said to be burned, usually it can not self-extinguish after being burned. Any insulation material with an oxygen limit index greater than 20.8% (oxygen partial pressure in the atmosphere) will not spontaneously ignite and support combustion. NOMEX? Paper 220 ° C time limit oxygen index is 22% - 25%. It is also greater than 21% at 300 °C. It does not support combustion and flame retardant at temperatures below 300 ° C. It can also self-extinguish after being exposed to an open flame. (See Figure 2) Of course it will not explode. NOMEX? Paper is free of toxins. After being burned, it will not release harmful gases. The temperature of the burning smoke is not high and the transparency is high. After the transformer is on fire, the temperature will be self-extinguishing when the temperature is lower than 300 °C. When the temperature is high, the combustion is non-toxic, and the temperature of the smoke is not high and the concentration is low. It does not pose a hazard to personnel, equipment and the environment during its manufacture, transportation, storage and operation.

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