6 Recent Developments in Electrical Insulation Systems for Generators and Transformers High-voltage equipment for power generation and transmission systems is continuously being developed to reduce production costs and improve efficiency, and recent demands have also been made to minimize the impact on the environment. In these devices, the most important performance is insulation. In order to operate the insulation system safely and reliably, the performance of the insulation material and the insulation structure are the most important words.
In order to allow the insulation system to operate safely and reliably, the performance of the insulation material and the insulation structure are the most important words. Over the past few decades, there have been a series of changes in high voltage insulation systems.
The application of 3 corpses 6 led to the development of 56 circuit breakers 013 and 01 D, etc. Excellent insulation performance and advanced technology make it applicable to high voltage cable insulators and other high voltage devices.
Recently, the existing technology has been applied in new fields. The high-voltage cable technology for transmission and distribution has now been used as a high-voltage winding in generators and transformers, resulting in a new type of high-voltage generator, which will hit 0 coffee 6 new The evaluation of the wind power system was also produced by the 0,1 and DryfonerTM oil-free power transformers.
Recent developments in transformer insulation systems have focused particularly on the comparison between insulation structures and insulation characteristics of conventional and new equipment.
In the original cable, the air was mainly made of natural rubber gutta percha and paraffin cotton rosin and bitumen, which was later impregnated with mineral oil. As more and more voltages are required, oil-filled cables have been developed to prevent partial discharges in the gaps. Today, two major electric power-impregnated liquid-impregnated paper cables and extruded polymer cables are used in transmission and distribution systems.
Extrusion cable insulation starts with thermoplastic polyethylene and is quickly replaced by chemically cross-linked polyethylene. The occupation of the entire industry is now commonly used in underground power distribution systems. Due to significant advances in this technology, transformers are quickly turned into applications. field.
Nowadays, the main components of power cables are the last few years, and the high-voltage insulation system has undergone a series of changes in the semiconducting layers inside and outside the conductor.
The insulating material has been modified to increase the electric field strength it withstands. For example, rotating electric motor power cable technology has a long history of power cable technology. Since the 1980s, extensive use of incandescent lighting systems has begun in the early 20th century with built-up edges and sheaths. The conductor is made of strands of copper or aluminum wire. The conductor is then covered with an insulating material. Finally, a metal sheath is added to the insulation.
The new application of cable technology is about doubled.
Good underground electrical insulation using insulated cables New insulation media have been introduced, for example, facilities.
0, 06, is that this kind of high-funded companies, or have the economic strength of the group or company acquisitions, the formation of new power electronics companies, so that enterprises have access to new development opportunities. Some companies actively undertake national key projects or military projects. They have obtained state funding and low-interest loans, and companies have achieved rapid development.
3 Product quality is the key to whether products can enter the international market.
At present, there is a certain gap between the quality of China's power electronics products and the quality of foreign large companies. We must make great efforts to improve the quality of our products and integrate them with international standards in order to remain invincible in the fierce international market competition.
From January 1987, he started to cooperate with domestic enterprises and discussed with the US users on China's power electronics export matters. Now, the company has been exploring for 15 years. In the future, Sencheng will further strengthen its cooperation with domestic companies to jointly develop overseas markets for China's power electronic devices. We firmly believe that in the era of Houding 0, there will be room for the development of China's power electronics companies in the world's markets. By then, the overseas agencies and sales agencies of China's power electronics companies will cover the world. Huifu's operating experience is another cable insulation system, but it does not require metal shielding and jacketing. In this application, the high-voltage cable winding is composed of a semi-conductive solid dielectric and an outer semi-conductive layer in the conductor. In the traditional cable terminology, it is often referred to as a cable core. The material and processing technology of this cable are used in the high-cable technology. In this way, it is virtually identical to the cable normally used in power transmission and distribution systems.
As in cable systems, new applications also require cable connectors and terminations because cables and cable accessories control the cable winding system to make the best choice. However, adapters are always used between cables of different insulation sizes, and the connectors are also different in various situations.
Applying this kind of high-voltage cable technology to generators and transformers is the core of the new insulation concept, which offers new possibilities for this equipment to improve its operating performance.
In conventional generators, the stator windings consist of square insulated conductor bars. Over the past 20 years, although the operating voltage to ground has increased, the changes in insulating materials and systems are relatively small. For generators that use mica tapes outside conductors and are impregnated with epoxy or polyester resin, today's field strength is 2.510. For insulation systems that use mica tapes, it is very important to have them in the manufacturing process. Keeping the insulation system free of voids, mechanical stress and thermal cycling can lead to the formation of voids. Therefore, as the voltage increases, partial discharge must occur within the insulation.
The beginning of the conventional stator bar is a rectangular unevenness, and the electric field intensity at the corner is high. In addition, complex measures must be taken at the end of the winding to control the electric field strength to avoid partial discharge and corona. This design principle of conventional generators does not allow the output voltage to exceed 3035, while the power transmission voltage has reached 800 or even higher. Power plants based on conventional generators often require step-up transformers.
Contrary to traditional generators, the winding of 0 comment 60161 is composed of extruded and another cable, which can avoid the electric field non-uniformity of the traditional insulation structure. The cable winding is a cylindrical conductor and the electric field distribution along the conductor plane is uniform. The stator slots can be machined to fit the shape of the cable winding with shielded insulation.
Nowadays, with this type of application, the insulated work field can reach 15, and the existing 500, cable facilities can achieve. Therefore, the new generator provides high-voltage generators that can directly connect to the voltage standard of the transmission system without the step-up transformer, and can also reduce the power loss and increase the effectiveness. The mechanical stress and the magnetic stress are separated. These basic design parameters can be optimally selected independently so that the materials associated therewith can be improved.
In the spring of 1998, prototypes for generators rated at 45 and 6001 were already in northern Sweden and the hydropower station was put into operation. Another station generator is either running or is under construction.
They are turbine generators with rated capacities of 136, 42 and 3,000,1 and 155, 75, and 125 rm hydroelectric generators.
Based on the evaluation technology of 0, 6 and 001, the wind power systems recently located in the offshore and coastal areas have developed a new type of wind power system, which has a typical power rating of 35 knots. Boundary ratio also, the basic design characteristics of 1 is that the stator is obtained from the basic principle of high-voltage cable winding from 0 to 6 to 00. The rotor is a permanent magnet, the rotor and turbine are directly coupled to a gearless box, and the DC current collection system.
The design of Innolux was optimized in terms of electrical circuits. For example, installing two rows of cable windings in each stator slot means that each phase does not require a cable connector. WindfomerTM is usually installed at sea or near shore. Therefore, all the materials used in the boundary printing industry must be carefully selected to prevent metal components from rusting and dielectric aging under severe environmental conditions.
In traditional power transformers, the insulation system consists mainly of mineral oil and cellulose paper, and it turns out that this combination has outstanding dielectric and thermal properties. In terms of the insulation system, this is a very effective combination. The dielectric strength of the paper and the oil itself is 40 and 12, respectively, claws, and the dielectric strength of the combination is 64 claws. However, for transformers, due to various reasons, its working field strength only allows 1.5, claws. Oil-paper insulation also has shortcomings, such as the risk of fire and explosion of dangerous oil that is blown.
The oil-paper insulation system of traditional transformers can only obtain good dielectric properties after a very thorough treatment process. In its natural state, paper or cardboard typically contains 510 tons of moisture; therefore, the first step of the process is a complete drying process at a high temperature of up to 130, and vacuum, so that the moisture content is reduced to about 5, and the first step of the process is to work. Component iron core. The winding fixtures and leads are vacuum impregnated to allow mineral oil to reach and fill all voids in the insulation system. Simply doing it completely may take two weeks. Therefore, science and technology developers have great interest in the dry design of power transformers. The two existing types are insulated 3-gas transformers and transformers made of molded epoxy glass fiber material.
The voltage rating of gas-insulated transformers can reach 275. With the improvement of environmental protection requirements, people hope to find a substitute for species 3. With molded epoxy glass fiber insulated transformers, the highest voltage level is only about 36kV, mainly because the internal field strength exceeds the partial discharge starting voltage. Because the newly introduced dry-type transformer 0,1 is neither oil nor paper, there is no danger associated with flammable oils, nor does it require an expensive fully dry process.
The difference between conventional transformers and 1 is not only in insulating materials but also in insulating structures.
For traditional power transformers, the insulation system consists of two parts, 4 insulation and turn-to-turn insulation. The main insulation is not only the transient over-voltage between the winding and the grounding component that must be subjected to lightning and circuit breaker switching, but also the AC electrical stress. For turn-to-turn insulation, the design requirements are primarily the effect of transient overvoltages. The electric field analysis of the inter-turn insulation model shows that the electric field strength is greatly increased in the oil gap between the winding edges. For the cable winding, the 7171 does not have such a question, because the outer semi-conductive layer is grounded, and the insulation of the cable winding only needs to function as a main insulation in a conventional transformer.
In addition, the combination of high-voltage cable technology and transformer technology can present the mechanical strength and heat-resistance limit of the dielectric strength winding of the insulation system in the traditional transformers of various components. In the new technology, different functionalities can be independently performed. To the best condition.
17,10 Single-phase transformers, the main purpose of the construction is to conceptualize and verify design ideas. The first stage is to find 1 Swedish for 6 such as hydropower stations for the 3 outings. The first stage has also been installed.
General characteristics of pressure-relieved cable windings 2 Contact resistance at the cable ground contact point is important.
The resistivity of the outer conductive layer of the conductive layer must be too high in a certain range, causing the potential between the two contact points of the semiconductive layer to be too high, and the resistivity being too low, resulting in increased power loss in the semiconductive layer. It is also important to maintain good contact between the semiconductive layer and the grounding system.
Windings For a new type of generator and transformer connected cable windings, the electric field strength gradually decreases along the straight ends of the cable windings to the neutral point under AC voltage. Therefore, in order to minimize the use of insulation, the cable winding can be composed of several high-voltage cables with different insulation thicknesses.
The distribution of the impulse voltage along the winding is different from that under the AC voltage. The insulation strength of the segment cable must be able to withstand transient overvoltages acting on the ends. The insulation thickness must also take this into account.
Workplace strength should pay attention to cable technology insulation design. Today's cable insulation materials and production technologies such as dry cross-linking. Ultra-clean production and re-extrusion can produce reliable cables with a working field strength of over 15,1. In the insulation design of new generators and transformers, the current work field strength is controlled to be around 10,1, which is selected according to the actual situation in the voltage range under consideration.
In the future, higher electric field strength will be introduced.
Such high electric field strength is not possible to achieve electric field distribution for conventional oil insulation based on mica and epoxy, so the insulation of the cable is fully utilized.
Mechanically, in order to avoid the wear of the outer semiconducting layer due to vibration, 0 comment 610 claw 1 In the gap between the cable and the slot wall is inserted silicone rubber corner, so that the cable winding is firmly fixed in the slot. The fixed force provided by the silicone rubber liner also accommodates the thermal expansion requirements of the cable insulation while also maintaining good contact between the outer semiconductive layer and the grounded stator core.
Rating 60 has its own characteristics in terms of groove design and winding method. Among them is that there are two rows of cable windings in each slot. Therefore, different methods are used to fix the cable in the slot.
The resistivity of the outer semiconductive layer of the 0016 cable winding is currently about 40. The high voltage generator developed by the transformer's large-scale wind turbine 188 company can be directly connected to the grid. Wen Li Liangui is the control surface potential and there is a point on the outside of the cable winding. AC grounding.
In terms of heat, the current in the 0-rated 6-door stator winding cable is very small, so the ratio of ohmic losses to iron losses is much lower than that of conventional generators. Most of the heat is generated by the fixed iron core at the ground potential. Greatly simplified cooling system. A water cooling circuit is installed in the stator core of the 6 to 016 stator to keep the system at an acceptable temperature.
In traditional transformers, oil is used as both an insulation and a cooling medium. Therefore, there is a disconnect between the two functions. However, for zero ice and claw 1, the connection between dielectric insulation and cooling is minimal, and an air-cooled or water-cooled system can be optimised as long as the operating temperature is maintained within the specified value.
Conclusion Mica epoxy and oil cellulose papers have dominated the insulation systems of rotating electrical machines and power transformers for many years. However, in recent years, cables have been introduced into generators and transformers as high-voltage windings, which has led to the creation of new generators, 016-wide, new-type wind power generation system evaluations, and new-type transformers, the Indochina 7. The new high-voltage generators and transformers have the characteristics of high efficiency and low impact on the environment, which gives new possibilities for the design of high-voltage equipment. The introduced products have the potential to use high-voltage electromagnetism to exploit the potential in equations.茗 Recently, the Swiss company Six 88 successfully developed a low-speed, high-voltage, large-capacity wind turbine that does not require a gearbox to increase the speed, and does not require transformer boost. This has brought about a century-long revolution in motor development. It is not limited to the field of wind power, and will be widely used on turbines and turbine generators, saving a lot of transformers.
Different from traditional wind turbines, this type of wind turbine, known as B10,1, adopts a large-diameter disc-type permanent magnet steel rotor instead of an asynchronous generator rotor through a gear box, and the stator winding adopts a circular high-voltage cable line. Instead of a rectangular section of copper wire. This circular high-voltage cable technology is a patented invention of the Swiss company 88. All stator windings are wound by a root cable, and there is no joint in the middle, which leads to high reliability. The generator voltage can reach more than 20, up to 400. The initial frequency of power generation is about 5 through the pole tube rectifier and the thyristor inverter to get 50 AC power of 2 frequency.
The stand-alone capacity of the new wind turbines is 3,5 cents. When the capacity is 3 circles, the center height of the wind turbine is 70, 3 blades, and each blade length is about 45 made of epoxy glass fiber reinforced plastic. The rotor diameter of a large-diameter disc-type permanent magnet steel with multi-pole structure is more than 6m, and the speed is about 18r min. In order to adapt to the sea, the permanent magnet steel uses anti-corrosion material. The unit can operate at a variable wind speed of 528 melons with a rated wind power of 13,18 hours. Below the rated wind speed, the blade angle is automatically adjusted to the effective position; when the wind speed is 18, 27 claws 5, the output power is reduced from 34 to 500 circles. When the wind speed averages 8 to 3, the annual power generation is about the limit.
Due to the omission of equipment such as gearbox transformers and starter power factor calibrators, the cost of this new type of unit is greatly reduced. At the same time, operation and maintenance costs are reduced, efficiency is improved, and availability is improved. And after the service life of the unit is over, effective materials can be recycled. The use of permanent magnet steel rotor material is also good for the environment. Due to the fact that more environmentally friendly materials are used, the advantages of this unit in favour of the ecological environment are outstanding.
The basis for the development of this new type of wind turbine is a zero-score, six-ten-to-one, hit 1 technology, that is, a high-voltage generator system that can be directly connected to the grid without the use of a step-up transformer, that is, a patented invention of a circular high-voltage cable. In addition to the first large-capacity wind turbines on the Nassudderr Offshore Wind Farm in Sweden to be installed and put into operation, this new technology was not used for the first time on a generator installed at the Poulis hydropower station on the Luray River in northern Sweden in May 1998. It can be directly connected to the grid without a transformer.
The EskUstuna 54kV high-voltage turbo-generator planned for operation by the end of 2000 will be a milestone in the application of this new high-voltage generator technology. In addition to the above-mentioned wind power, hydropower and thermal power new products, this new technology can also be used for technical transformation of old products. Therefore, this can increase output power by 20 and reduce maintenance costs by half. The focus of the sector's power generation equipment industry has caused a sensation in recent international major power grid conferences. Compliance
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