As the supply and demand of electricity tends to be balanced and affluent, the construction of power grids will develop rapidly during the “Eleventh Five-Year Plan†period. Construction of UHV power grids, skeletal power grids, and cross-regional power transmission projects will be the top priority for power grid construction. According to the plans of the State Grid Corporation of China In 2010, the national transmission capacity of UHV and cross-regional grids was about 70 million kilowatts, and the amount of power transmission was about 350 billion kwh. The scale was about three times that of 2005. The construction of large-scale pit power stations and the large-scale development of hydropower are an important driving force for cross-regional power grid construction. According to national plans, during the “Eleventh Five-Year†and “Twelfth Five-Year Plan†period, China’s hydropower development will be basically completed, taking into account the western region. Most of the hydropower bases are far away from the load center. Therefore, it is necessary to realize the intensive development and delivery of these western hydropower bases through long-distance transmission, especially the construction of UHV DC point-to-point transmission projects.
(I) Analysis of Future Market Development According to the State Grid Corporation's “11th Five-Year Plan†power network planning and 2020 long-term goal report, during the “11th Five-Year Plan†period, the State Grid Corporation will add 60,000 kV and above transmission lines to 60,000 kilometers. With a capacity of 300 million kVA, it will have an investment of about 900 billion yuan. By 2010, the trans-regional transmission capacity will reach more than 40 million kilowatts, and the transmission of electricity will exceed 180 billion kilowatt-hours. During the “Eleventh Five-Year Plan†period, the State Grid Corporation invested an average of 180 billion yuan each year, taking into account that China Southern Power Grid Corporation’s investment is generally 1/3 to 1/4 of that of the State Grid Corporation, and the total investment of the State Grid and China Southern Power Grid may reach 225 billion yuan. Compared with the “10th Five-year Planâ€, the increase rate has reached 90%, and the electrical equipment and power transmission and transformation equipment industry are facing brighter development prospects. Our consulting experts believe that China's transformer industry has two main directions of development: First, it is developing in the direction of high pressure and ultra high voltage, especially 750 kV and 1100 kV. The second is the development of energy-saving and miniaturization. The former is mainly applied to long-distance power transmission and transmission lines, and the latter is mainly used in urban power transmission and transmission lines. The market capacity of distribution transformers is relatively large, but due to low technical barriers, numerous manufacturers, and small enterprises, the industry concentration is low, and market competition is still fierce. But overall, the development opportunities in the distribution transformer industry are greater than the difficulties. China Business Intelligence Network expects that by 2010, the demand for dry-type transformers in China will reach 50 million kVA.
China's annual installed power generation capacity exceeds 30 GW, and the corresponding new transformer capacity is a multiple of the power generation capacity. In the past, it was generally considered as 11 times, now it can reach 13 times, and even exceeds, that is to say, the annual output of transformers is required. More than 400GVA, according to the analysis of China Electrical Equipment Industry Association, transformers are expected to complete 600GVA in 2007, an increase of 9% year-on-year. In recent years, China's power grid construction and reconstruction funds have exceeded 100 billion yuan each year, plus the use of electrical equipment in power plant projects. Electric equipment, booster station equipment, protection and monitoring equipment generally account for 16% to 20% of investment in power station equipment.
(II) Future market technology development direction At present, the transmission and distribution system is facing some new problems, such as the degree of environmental protection will be increasingly greater, due to electromagnetic interference, noise, and high voltage, ultra-high voltage transmission lines and substations may generate electromagnetic interference. Problems such as electrostatic induction and landscape coordination, and the construction land required for new transmission lines and substations are also limited; due to the imbalance of energy distribution and economic development, large-capacity long-distance power transmission still has a relatively strong development momentum; the huge benefit of grid interconnection operation The trend of large-scale power grid interconnection and cross-border interconnection of power transmission is also developing; the reform of power system marketization is being gradually implemented on a global scale, and power users are demanding higher and higher power quality (anti-flicker and harmonic reduction).
This requires the transmission and distribution system to have good environmental performance, high reliability, high power quality, and flexible control of the trend, and requires the transmission and distribution equipment to adapt to the new characteristics of the future power system and meet the new requirements of the power system. . The development trend of power transmission and distribution technology is roughly:
1. In order to realize long-distance and high-volume AC transmission, the voltage level of AC transmission gradually increases. At the end of the 1960s, the AC transmission voltage has been increased to 735kV, 765kV and 800kV, and 345kV has been built in many countries. , 400kV, 500kV, 750kV, 800kV power grid.
2. The HVDC transmission technology has developed rapidly. The main advantages of HVDC transmission technology are: it is suitable for long-distance transmission; it does not increase the short-circuit capacity of the system; it facilitates the non-synchronized networked operation of two large power systems and the interconnection of power systems with different frequencies. Using power modulation of the DC system can improve the damping of the power system, suppress low-frequency oscillations, and increase the transmission capacity of the AC power transmission lines running in parallel.
The cost of DC transmission lines is lower than that of AC transmission lines, but the cost of converter stations is much higher than that of AC substations. It is generally believed that overhead lines exceed 600-800 km and cable lines exceed 40-60 km. DC transmission is more economical than AC transmission. With the development of high-voltage and large-capacity thyristors and control and protection technologies, the cost of converter equipment has gradually decreased, and DC transmission has developed rapidly in recent years.
From the “Eleventh Five-Year Plan†to 2020, there are more than 10 HVDC projects planned to be built in China. The DC transmission at both ends of the country is already a mature technology. Moreover, multi-end DC transmission technology has been researched. Now, three-terminal DC transmission has been operating in Canada. Light-duty DC transmission is also under development, and light DC transmission has been researched and applied abroad (ABB called HVDCLight, and Siemens called HVDCPlus). Light-duty DC transmission system, which uses components such as GTO and IGBT that can be turned off to form a converter, eliminating the need for a converter transformer and allowing the entire converter station to be relocated, enabling medium-capacity HVDC transmission projects to be operated at shorter distances. Can compete with AC transmission. In addition, the devices that can be turned off compose the inverter. Since the power electronics can be turned off, the problem of commutation failure can be eliminated, and there is no requirement for the capacity of the receiver system, so it can be used for isolated small systems (offshore oil platforms). Power supply for islands and islands can be used in the future for urban power distribution systems and for access to distributed power sources such as fuel cells, photovoltaic power generation (Photovoltaic Power Generation).
At present, the domestic UHV DC transmission project converter station equipment is mainly provided by ABB and Siemens, domestic companies such as Western Electric have been introducing technology for localization. The number of newly-built DC transmission lines is now relatively large, which also requires the acceleration of the localization of HVDC transmission equipment.
3. About Flexible AC Transmission System Technology (FACTS)
About flexible AC transmission technology (also known as flexible AC transmission technology) is based on power electronic technology and modern control technology on the AC transmission system impedance, voltage, phase implementation of flexible and rapid adjustment of transmission technology, can improve the AC transmission system controllability, Transmission capacity and stability.
The Flexible AC Transmission System Technology (FACTS) is known as a product of the "second silicon revolution" of power system control technology. The development of power grids and the need for large-scale interconnected power grids to control the power system's power flow and its stability, coupled with advances in power electronics technology, has greatly advanced the development and application of new transmission technologies—flexible AC transmission system technologies.
4. Compact transmission technology. The compact transmission technology reduces the phase distance between transmission lines and changes the arrangement, thereby reducing the line reactance, increasing capacitive reactance, and increasing the rated natural power under the condition that the line rated voltage is constant. A more economical transmission technology that improves the UHV AC transmission capability. In 1999, a 500 kV compact test transmission line (Changping--Fangshan) was built in North China in China and was 85 km long. The sub-conductor was a six-split structure (such as 6x240 mmz), and the diameter of the ring was 750 mm. The phase sequence was inverted triangle and the distance between phases was 6.7 m. The distance between the conductor and the ground is 10m, and the corridor width is 16m. The natural power is increased by 1/3 compared to the conventional line. The compact transmission line should be installed with shunt reactors at appropriate positions on the line, and the capacity of the reactor should be controlled so that it can be based on The load changes of the line make the reactive power flow of the system achieve dynamic balance and ensure the dynamic stability of the power grid. The controllable reactors used in such compact transmission lines are the key equipments that need to be autonomously produced.
5. Large-capacity power transmission and distribution equipment Large-capacity power transmission and distribution equipment are: large-capacity transformer refers to 500kV, l000MVA or more transformers, mainly to meet the needs of large-capacity central power supply, saving the land used by substations, currently China's load-intensive This type of 500kV, 1000MVA large-capacity transformer has been used in East China and Nanjing Power Grids one after another. Large-section cable, such as 220kV, 2500mm2 power cable; 2x630m.mz above the large-area overhead wire and large cross-section heat-resistant wire development and application. Breakage capacity is 63kA and above circuit breaker manufacturing.
6. Gas insulated transmission lines (GIL)
The transmission capacity of SF6 gas insulated transmission lines is greater than the cable transmission lines, which can be laid on the ground and underground, and the cost is lower than the cable line. At present, some major transmission and distribution manufacturers in the world have developed gas-insulated transmission lines.
7. Development prospects for high-temperature superconducting power transmission A high-temperature superconducting project between the US Department of Energy and Southern Wire Corporation is 100ft (lft=0.3048m), 3-phase power cable system. The next decade is a decade of market development and material industrialization of high-temperature superconductors (including generators, transformers, motors, cables, etc.). It is predicted that in 2010 and 2020, the world superconducting market will reach US$30 billion/year and US$244 billion/year, respectively.
8. High-integration, compact, and intelligent transmission and distribution equipment Compact transmission and distribution equipment is the most representative of the gas-insulated switchgear (GIS) used in high-voltage, ultra-high-pressure systems, open combination switchgear , As well as inflatable chamber cabinets (C-GIS), inflatable ring main units, etc. used in medium-pressure systems. In order to meet the needs of the modernization of substations for miniaturization and automation, primary equipment (such as circuit breakers, disconnectors, earthing switches, current and voltage transformers, surge arresters, etc.) and secondary equipment (intelligent protection, measurement, and High-integration, compact power transmission and distribution equipment, such as ABB's PASS system and Siemens' HIS system. It has been developed abroad as a high-voltage generator using a cable-winding (stator) (known abroad as the Powerformer, whose output voltage is 132kV or higher, and the conventional large-capacity generator has an output voltage of 20kV). Power can be delivered without a step-up transformer, greatly simplifying the power station's boost station. The converter station equipment and flexible AC transmission equipment for UHVDC transmission are also the perfect integration of high-voltage, ultra-high-voltage large-capacity power conversion, control and digital monitoring technologies. In the modern power system's automatic monitoring system, each power transmission and distribution device at the equipment level will become the terminal equipment of the computer monitoring system, and realize the information exchange with the substation's bay level, station control layer and network management layer. The high reliability, maintenance-free, intelligent, communicable, on-line monitoring and remote fault diagnosis of power transmission and distribution equipment will be the trend.
9. New type of flexible and reliable intelligent power distribution system The future power distribution system can provide multi-quality "flexible", "reliable", "agile" and "perfect" electrical energy services according to the needs of different users; It is also free to choose the power quality, type and supplier. The system has a perfect distributed power supply and energy storage system to ensure uninterrupted power supply; perfect demand side management and real-time bidirectional transmission of information and so on. The current distribution management automation system (DMS) is a very fast-growing area, including the SCADA of power distribution systems, load control, automatic fault isolation, automatic reactive compensation, power consumption management, and equipment management.
10. Pay attention to the environmental performance of power transmission and distribution equipment. Pay attention to the environmental performance of the product. Pay particular attention to the use of less SF6 gas (because SF6 gas will produce a greenhouse effect). Foreign countries have begun to use nitrogen, some nitrogen and some SF6 gas mixture instead SF6 gas and other programs. Contactors and other contacts do not use silver niobium alloys (ie, silver niobium oxide, AgCdO, silver tin oxide has been used abroad, AgSnO2 instead) and other issues. The "Regarding Waste Electrical and Electronic Equipment Directive" and the "Restriction on the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" clearly require that starting from July 1, 2006, new electronic and electrical equipment placed on the market should not include lead, mercury, Hexavalent chromium, hexavalent chromium, polyphenylene oxide (PBB) and polyphenylene oxide (PBDE) are six harmful substances. Therefore, in the contact materials of low-voltage electrical appliances and relays, if the use of brocade, such as silver oxidized blessing, should gradually adopt the contact without helium component.
To reduce the noise of power transformers and reactors, develop and use low-noise fans and oil pumps, develop low-noise reactors, and pay attention to research on electromagnetic compatibility of transmission and distribution equipment. Attention to substation equipment landscape design and coordination issues.
(I) Analysis of Future Market Development According to the State Grid Corporation's “11th Five-Year Plan†power network planning and 2020 long-term goal report, during the “11th Five-Year Plan†period, the State Grid Corporation will add 60,000 kV and above transmission lines to 60,000 kilometers. With a capacity of 300 million kVA, it will have an investment of about 900 billion yuan. By 2010, the trans-regional transmission capacity will reach more than 40 million kilowatts, and the transmission of electricity will exceed 180 billion kilowatt-hours. During the “Eleventh Five-Year Plan†period, the State Grid Corporation invested an average of 180 billion yuan each year, taking into account that China Southern Power Grid Corporation’s investment is generally 1/3 to 1/4 of that of the State Grid Corporation, and the total investment of the State Grid and China Southern Power Grid may reach 225 billion yuan. Compared with the “10th Five-year Planâ€, the increase rate has reached 90%, and the electrical equipment and power transmission and transformation equipment industry are facing brighter development prospects. Our consulting experts believe that China's transformer industry has two main directions of development: First, it is developing in the direction of high pressure and ultra high voltage, especially 750 kV and 1100 kV. The second is the development of energy-saving and miniaturization. The former is mainly applied to long-distance power transmission and transmission lines, and the latter is mainly used in urban power transmission and transmission lines. The market capacity of distribution transformers is relatively large, but due to low technical barriers, numerous manufacturers, and small enterprises, the industry concentration is low, and market competition is still fierce. But overall, the development opportunities in the distribution transformer industry are greater than the difficulties. China Business Intelligence Network expects that by 2010, the demand for dry-type transformers in China will reach 50 million kVA.
China's annual installed power generation capacity exceeds 30 GW, and the corresponding new transformer capacity is a multiple of the power generation capacity. In the past, it was generally considered as 11 times, now it can reach 13 times, and even exceeds, that is to say, the annual output of transformers is required. More than 400GVA, according to the analysis of China Electrical Equipment Industry Association, transformers are expected to complete 600GVA in 2007, an increase of 9% year-on-year. In recent years, China's power grid construction and reconstruction funds have exceeded 100 billion yuan each year, plus the use of electrical equipment in power plant projects. Electric equipment, booster station equipment, protection and monitoring equipment generally account for 16% to 20% of investment in power station equipment.
(II) Future market technology development direction At present, the transmission and distribution system is facing some new problems, such as the degree of environmental protection will be increasingly greater, due to electromagnetic interference, noise, and high voltage, ultra-high voltage transmission lines and substations may generate electromagnetic interference. Problems such as electrostatic induction and landscape coordination, and the construction land required for new transmission lines and substations are also limited; due to the imbalance of energy distribution and economic development, large-capacity long-distance power transmission still has a relatively strong development momentum; the huge benefit of grid interconnection operation The trend of large-scale power grid interconnection and cross-border interconnection of power transmission is also developing; the reform of power system marketization is being gradually implemented on a global scale, and power users are demanding higher and higher power quality (anti-flicker and harmonic reduction).
This requires the transmission and distribution system to have good environmental performance, high reliability, high power quality, and flexible control of the trend, and requires the transmission and distribution equipment to adapt to the new characteristics of the future power system and meet the new requirements of the power system. . The development trend of power transmission and distribution technology is roughly:
1. In order to realize long-distance and high-volume AC transmission, the voltage level of AC transmission gradually increases. At the end of the 1960s, the AC transmission voltage has been increased to 735kV, 765kV and 800kV, and 345kV has been built in many countries. , 400kV, 500kV, 750kV, 800kV power grid.
2. The HVDC transmission technology has developed rapidly. The main advantages of HVDC transmission technology are: it is suitable for long-distance transmission; it does not increase the short-circuit capacity of the system; it facilitates the non-synchronized networked operation of two large power systems and the interconnection of power systems with different frequencies. Using power modulation of the DC system can improve the damping of the power system, suppress low-frequency oscillations, and increase the transmission capacity of the AC power transmission lines running in parallel.
The cost of DC transmission lines is lower than that of AC transmission lines, but the cost of converter stations is much higher than that of AC substations. It is generally believed that overhead lines exceed 600-800 km and cable lines exceed 40-60 km. DC transmission is more economical than AC transmission. With the development of high-voltage and large-capacity thyristors and control and protection technologies, the cost of converter equipment has gradually decreased, and DC transmission has developed rapidly in recent years.
From the “Eleventh Five-Year Plan†to 2020, there are more than 10 HVDC projects planned to be built in China. The DC transmission at both ends of the country is already a mature technology. Moreover, multi-end DC transmission technology has been researched. Now, three-terminal DC transmission has been operating in Canada. Light-duty DC transmission is also under development, and light DC transmission has been researched and applied abroad (ABB called HVDCLight, and Siemens called HVDCPlus). Light-duty DC transmission system, which uses components such as GTO and IGBT that can be turned off to form a converter, eliminating the need for a converter transformer and allowing the entire converter station to be relocated, enabling medium-capacity HVDC transmission projects to be operated at shorter distances. Can compete with AC transmission. In addition, the devices that can be turned off compose the inverter. Since the power electronics can be turned off, the problem of commutation failure can be eliminated, and there is no requirement for the capacity of the receiver system, so it can be used for isolated small systems (offshore oil platforms). Power supply for islands and islands can be used in the future for urban power distribution systems and for access to distributed power sources such as fuel cells, photovoltaic power generation (Photovoltaic Power Generation).
At present, the domestic UHV DC transmission project converter station equipment is mainly provided by ABB and Siemens, domestic companies such as Western Electric have been introducing technology for localization. The number of newly-built DC transmission lines is now relatively large, which also requires the acceleration of the localization of HVDC transmission equipment.
3. About Flexible AC Transmission System Technology (FACTS)
About flexible AC transmission technology (also known as flexible AC transmission technology) is based on power electronic technology and modern control technology on the AC transmission system impedance, voltage, phase implementation of flexible and rapid adjustment of transmission technology, can improve the AC transmission system controllability, Transmission capacity and stability.
The Flexible AC Transmission System Technology (FACTS) is known as a product of the "second silicon revolution" of power system control technology. The development of power grids and the need for large-scale interconnected power grids to control the power system's power flow and its stability, coupled with advances in power electronics technology, has greatly advanced the development and application of new transmission technologies—flexible AC transmission system technologies.
4. Compact transmission technology. The compact transmission technology reduces the phase distance between transmission lines and changes the arrangement, thereby reducing the line reactance, increasing capacitive reactance, and increasing the rated natural power under the condition that the line rated voltage is constant. A more economical transmission technology that improves the UHV AC transmission capability. In 1999, a 500 kV compact test transmission line (Changping--Fangshan) was built in North China in China and was 85 km long. The sub-conductor was a six-split structure (such as 6x240 mmz), and the diameter of the ring was 750 mm. The phase sequence was inverted triangle and the distance between phases was 6.7 m. The distance between the conductor and the ground is 10m, and the corridor width is 16m. The natural power is increased by 1/3 compared to the conventional line. The compact transmission line should be installed with shunt reactors at appropriate positions on the line, and the capacity of the reactor should be controlled so that it can be based on The load changes of the line make the reactive power flow of the system achieve dynamic balance and ensure the dynamic stability of the power grid. The controllable reactors used in such compact transmission lines are the key equipments that need to be autonomously produced.
5. Large-capacity power transmission and distribution equipment Large-capacity power transmission and distribution equipment are: large-capacity transformer refers to 500kV, l000MVA or more transformers, mainly to meet the needs of large-capacity central power supply, saving the land used by substations, currently China's load-intensive This type of 500kV, 1000MVA large-capacity transformer has been used in East China and Nanjing Power Grids one after another. Large-section cable, such as 220kV, 2500mm2 power cable; 2x630m.mz above the large-area overhead wire and large cross-section heat-resistant wire development and application. Breakage capacity is 63kA and above circuit breaker manufacturing.
6. Gas insulated transmission lines (GIL)
The transmission capacity of SF6 gas insulated transmission lines is greater than the cable transmission lines, which can be laid on the ground and underground, and the cost is lower than the cable line. At present, some major transmission and distribution manufacturers in the world have developed gas-insulated transmission lines.
7. Development prospects for high-temperature superconducting power transmission A high-temperature superconducting project between the US Department of Energy and Southern Wire Corporation is 100ft (lft=0.3048m), 3-phase power cable system. The next decade is a decade of market development and material industrialization of high-temperature superconductors (including generators, transformers, motors, cables, etc.). It is predicted that in 2010 and 2020, the world superconducting market will reach US$30 billion/year and US$244 billion/year, respectively.
8. High-integration, compact, and intelligent transmission and distribution equipment Compact transmission and distribution equipment is the most representative of the gas-insulated switchgear (GIS) used in high-voltage, ultra-high-pressure systems, open combination switchgear , As well as inflatable chamber cabinets (C-GIS), inflatable ring main units, etc. used in medium-pressure systems. In order to meet the needs of the modernization of substations for miniaturization and automation, primary equipment (such as circuit breakers, disconnectors, earthing switches, current and voltage transformers, surge arresters, etc.) and secondary equipment (intelligent protection, measurement, and High-integration, compact power transmission and distribution equipment, such as ABB's PASS system and Siemens' HIS system. It has been developed abroad as a high-voltage generator using a cable-winding (stator) (known abroad as the Powerformer, whose output voltage is 132kV or higher, and the conventional large-capacity generator has an output voltage of 20kV). Power can be delivered without a step-up transformer, greatly simplifying the power station's boost station. The converter station equipment and flexible AC transmission equipment for UHVDC transmission are also the perfect integration of high-voltage, ultra-high-voltage large-capacity power conversion, control and digital monitoring technologies. In the modern power system's automatic monitoring system, each power transmission and distribution device at the equipment level will become the terminal equipment of the computer monitoring system, and realize the information exchange with the substation's bay level, station control layer and network management layer. The high reliability, maintenance-free, intelligent, communicable, on-line monitoring and remote fault diagnosis of power transmission and distribution equipment will be the trend.
9. New type of flexible and reliable intelligent power distribution system The future power distribution system can provide multi-quality "flexible", "reliable", "agile" and "perfect" electrical energy services according to the needs of different users; It is also free to choose the power quality, type and supplier. The system has a perfect distributed power supply and energy storage system to ensure uninterrupted power supply; perfect demand side management and real-time bidirectional transmission of information and so on. The current distribution management automation system (DMS) is a very fast-growing area, including the SCADA of power distribution systems, load control, automatic fault isolation, automatic reactive compensation, power consumption management, and equipment management.
10. Pay attention to the environmental performance of power transmission and distribution equipment. Pay attention to the environmental performance of the product. Pay particular attention to the use of less SF6 gas (because SF6 gas will produce a greenhouse effect). Foreign countries have begun to use nitrogen, some nitrogen and some SF6 gas mixture instead SF6 gas and other programs. Contactors and other contacts do not use silver niobium alloys (ie, silver niobium oxide, AgCdO, silver tin oxide has been used abroad, AgSnO2 instead) and other issues. The "Regarding Waste Electrical and Electronic Equipment Directive" and the "Restriction on the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" clearly require that starting from July 1, 2006, new electronic and electrical equipment placed on the market should not include lead, mercury, Hexavalent chromium, hexavalent chromium, polyphenylene oxide (PBB) and polyphenylene oxide (PBDE) are six harmful substances. Therefore, in the contact materials of low-voltage electrical appliances and relays, if the use of brocade, such as silver oxidized blessing, should gradually adopt the contact without helium component.
To reduce the noise of power transformers and reactors, develop and use low-noise fans and oil pumps, develop low-noise reactors, and pay attention to research on electromagnetic compatibility of transmission and distribution equipment. Attention to substation equipment landscape design and coordination issues.
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