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电力系统的构成(Constitution of electric power system)

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内容提示: 电力系统的构成(Constitution of electric power system) First, the constitution of the electric power system A complete power system consists of various types of distribution around the power plant, the step-up and step-down substation, transmission lines and power users, they are complete electrical production, voltage transformation, power transmission and distribution and use of energy. Two. The division of power network, power system and power system Power network: a network composed of power transmissi...

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电力系统的构成(Constitution of electric power system) First, the constitution of the electric power system A complete power system consists of various types of distribution around the power plant, the step-up and step-down substation, transmission lines and power users, they are complete electrical production, voltage transformation, power transmission and distribution and use of energy. Two. The division of power network, power system and power system Power network: a network composed of power transmission equipment, substation equipment and distribution equipment. Power system: on the basis of the power grid with power generation equipment. Power system: Based on the power system, the power plant parts (such as thermal power plant boiler, steam turbine and hydro power plant reservoir, hydraulic turbine and nuclear power plant reactor etc.) are included in the system. Three. Characteristics of power system operation First, the total amount of the economy is large. At present, China's power industry asset size has more than 2 trillion, accounted for a total of 1/4 of the state-owned assets, electricity production directly affects the healthy development of the national economy. The two is at the same time, a large number of electricity can not be stored, unity composed of all sectors can not be separated, the transition process is very rapid, instant production power must be equal to the moment for every aspect of power, so the power production of the power generation, transmission and distribution are very important to the user. The three is concentrated, electricity production is highly centralized and unified, no matter how many power plants, power companies, power grid must be unified, unified management, unified management; safety production, organization and discipline, occupation morality has strict requirements. Four is applicability, the service object of power industry is all-round, involving all the population in the whole society, power quality, electricity price level is closely related to the interests of the vast number of power users. Five is advance, the development of national economy power must go ahead of the rest. Four. Rated voltage of power system There is a level of power grid voltage, rated voltage is reasonable according to the needs of national economic development, technology economy and electrical equipment manufacturing level, through the comprehensive analysis and demonstration, enacted by the national unity. The voltage levels of our country's power system are 220/380V, 3 kV, 6 kV, 10 kV, 20 kV, 35 kV, 66 kV, 110 kV, 220 kV, 330 kV, 500 kV. With the increasing demand for standardization, 3 kV, 6 kV, 20 kV and 66 kV are rarely used. The power supply system is mainly composed of 10 kV and 35 kV. The transmission and distribution system is mainly composed of 110 kV or more. Generators in the past have 6 kV and 10 kV two kinds, now 10 kV based, low voltage users are 220/380V. The rated voltage of the power equipment is consistent with the rated voltage of the power grid. In fact, due to the voltage loss in power grid, resulting in the actual voltage rated value, in order to ensure the good operation of electrical equipment, electrical equipment should be clearly compared with the grid voltage deviation to allow a wider range of working voltage. The rated voltage of generators is generally 5% higher than the rated voltage of the same power grid, which is used to compensate the voltage loss on the power grid. The rated voltage of transformer is divided into primary and two windings. For a winding, when the transformer is connected to power grid at the end of a load equal to the power grid on the properties (such as factory transformer), the rated voltage and the power grid, when the transformer is connected to the generator terminals (such as when the power plant step-up transformer), the rated voltage should be the same as the generator rated voltage. For the two time in consideration of transformer winding, bearing its voltage loss (at 5%), two times the rated voltage of transformer winding should be 5% higher than the rated voltage of power grid, when the two side of the transmission distance is long, but also should consider the loss of line voltage (at 5%), at this time, the two winding rated voltage should be 10% higher than the rated voltage of power grid. Five. Neutral operation mode of power system In power system, the system of neutral point direct grounding or neutral grounding through small impedance (small resistance) is called high current grounding system, The system of ungrounded neutral or neutral grounding by arc suppression coil is called small current grounding system. The operation mode of neutral point mainly depends on the insulation requirement of electrical equipment and the reliability of power supply in single phase grounding. Comparison of advantages and disadvantages of various operation modes Neutral point direct grounding mode: when a relative ground insulation failure occurs, that is a single-phase short-circuit, power supply interruption, the reliability is reduced. However, under this mode, the relative voltage of the non fault is constant, and the insulation level of the electrical equipment can be considered according to the phase voltage. The 220V/380V and 110KV in our country are grounded directly by neutral point system in higher system and operated in high current grounding mode. Ungrounded or grounded by arc suppression coil: when single-phase grounding fault occurs, the line voltage is constant, and the non fault phase voltage to phase voltage of the original tick 3 times, uninterrupted power supply, high reliability. Our country's 10KV and 35KV systems use neutral ungrounded or arc suppression coil grounding, operating in small current grounding mode. Six. Quality of power supply Voltage, frequency and reliability are the indicators that determine the quality of customer power supply. 1. voltage The ideal supply voltage should be a three-phase symmetrical sinusoidal voltage whose amplitude is constant. Due to the presence of impedance, power supply system with the change of power load and electricity load properties and other factors, the actual supply voltage regardless of the amplitude, waveform and phase symmetry and ideal voltage exists between the deviation. (1) voltage deviation: the voltage deviation refers to the difference between the actual voltage and the rated voltage, and the actual voltage is too high or low, which has an impact on the good operation of the power equipment. The permissible value of voltage deviation is stipulated by the national standard: The sum of the absolute value of the positive and negative voltage deviation is no more than 10% of the rated voltage when the voltage is supplied by a, 35 thousand volts and above; B, 10 thousand volts and below three-phase power supply, the allowable voltage deviation is rated voltage of + 7%. In the C, 220 volts single-phase power supply, voltage deviation is rated voltage of +7%, -10%. Calculation formula Voltage deviation (%) = (actual voltage one rated voltage) / rated voltage, and finally multiplied by 100% (2) voltage fluctuation and flicker: in a certain period of time, the phenomenon that voltage changes rapidly and deviates from the rated value is called voltage fluctuation. When the arc furnace and other large capacity impact load operation, the change of the load current will cause the change of the line voltage drop, which leads to voltage fluctuation in the power grid. The flicker of light caused by voltage fluctuation, the rapid fluctuation of luminous flux, and the stimulation of human brain are called voltage flicker. The allowable value of the national standard for voltage fluctuation is: 10KV and below is 2.5% 35 to 110KV was 2% 220KV and above were 1.6% (3) the generation of high-order harmonic: the nonlinear electrical equipment is put into operation in the power grid, which makes the voltage and current waveform of the grid distorted in different degrees and deviates from the sine wave. In addition to the background harmonics of the power system, high order harmonics are mainly caused by nonlinear power equipment, such as high-power converter equipment, electric arc furnace and so on. The existence of higher harmonics leads to the increase of energy consumption of power supply system, the accelerated aging of electrical equipment insulation, and interference with the normal operation of automation devices and communication facilities. (4) three-phase asymmetry: three-phase voltage asymmetry refers to the difference of amplitude and phase relation between three phase voltages. Three phase asymmetry is mainly caused by asymmetric operating parameters of the system and unbalanced three-phase load. The asymmetric operation of power supply system is harmful to the power supply equipment and power supply and distribution system, and the asymmetric operation of the low-voltage system will lead to neutral point offset, thus endangering the safety of people and equipment. Under the normal operation mode of the power system public connection point, the allowable value of the imbalance is 2%, not exceeding 4% for a short time, and the single user shall not exceed 1.3% Allowable deviation of 2. power supply frequency The frequency of alternating current generated by the generator in the grid is called frequency, and the standard frequency 50HZ. is specified in China China's national standard stipulates that the allowable value of the normal frequency deviation of the power system is + 0.1Hz, and when the system capacity is less than 300Mv, the deviation value can be relaxed to + 0.5Hz. 3. reliability of power supply The reliability rate of power supply refers to the time and frequency of the power failure of the power supply enterprise in a certain statistical period, which directly reflects the continuous power supply capacity of the power supply enterprise. Power supply reliability rate reflects the national economy can meet the power needs of the electric power industry, has become one of the standard measure of a country's level of economic development; the power supply reliability can be measured with the following year a series of indicators: power supply reliability rate, the average user outage time, user average power frequency, the average user fault outage times. The power supply reliability rate of the city is 99.96/100. That is, the average annual outage time is not more than 3.5 hours; The reliability rate of power supply in China has reached 3 9 (above 99.9%) in general urban areas, the average annual outage time of users is not more than 9 hours, and the important urban central areas have reached 4 9 (99.99%) above, the average annual outage time of the user is not more than 53 minutes. Calculation formula Power supply reliability rate (%) =8760 (annual power supply hours) - annual outage hours /8760, and finally multiplied by 100% Classification of electric load Power load: the sum of the actual power consumed by the user's electrical equipment at a given moment. There are many kinds of power load classification methods. The most significant is to classify the load according to the time of the load in the power system and the degree of loss caused by the sudden interruption of power supply. Load classification by time 1, peak load: refers to the maximum load in a day or the power grid load. The average load of the highest one hour in 24 hours is the highest load, usually 1 months daily peak load, one month peak load and so on. 2, minimum load: refers to the power grid or the user in the day within 24 hours of the lowest power consumption load. There are usually 1 months daily minimum load, one month minimum load and so on. 3, average load: refers to the average power consumption of the power grid or the user in a certain period of time. Classification of loss degree caused by interruption of power supply 1, a load: a sudden power outage will cause casualties or cause serious pollution to the surrounding environment, causing huge economic losses, such as large important equipment damage, important products or raw materials for the production of a large number of scrap products, continuous production process is disrupted, it takes a long time to resume production; and a sudden power outage will cause serious public disorder or in politics have significant adverse effects, such as the electricity load important transportation and communication hub, international social places etc.. 2, two load: a sudden power outage in the economy will cause more losses, such as the production of major equipment damage, large number of scrapped products or production, continuous production process takes a long time to recover; and a sudden power failure can cause social disorder or in politics caused great influence, such as transportation and communications hub, the city's main water source electricity load, radio and television, business center etc.. 3 and three load: not belong to the first and two level load. Seven. Substation Substation is the intermediate link connecting power system to collect power supply, lift voltage and distribute power. Main wiring of Substation Substation is the main connection of the main electrical equipment, by the generator, transformer, circuit breaker, isolating switch and other electrical equipment through the bus conductor, link, and configuration of various transformer, lightning arrester protection measuring appliance, a system of collection and distribution of electric energy. The main wiring form of substation is closely related to the selection, layout, reliability and economy of substation equipment, and the configuration of relay protection. It is an important link of substation design. When drawing up the main wiring scheme of substation, it should meet the basic requirements of reliability, simplicity, safety, flexible operation, reasonable economy, convenient operation and maintenance, and adaptive development. Eight, power supply Power generation is mainly produced by generators. At present, the main power generation modes in the world are thermal power generation, hydro power generation and nuclear power generation. Other small capacity wind, geothermal, solar, tidal and so on. 1, thermal power: the use of coal, oil and natural gas and other fossil fuels power generation methods collectively referred to as thermal power generation. According to the power generation mode, the thermal power generation is divided into coal-fired turbine power generation, fuel turbine power generation, gas steam combined cycle power generation and internal combustion engine power generation. Thermal power plants, referred to as thermal power plants, are factories that use coal, oil, natural gas, or other fuels to produce electrical energy. Thermal power plants are mainly composed of: (1) boilers and auxiliary equipment to ensure that the chemical energy of fuel is converted into heat energy. (2) steam turbines and auxiliary equipment to ensure that heat energy is converted into mechanical energy. (3) generator and exciter to ensure that mechanical energy is changed into electric energy. (4) the main transformer, the electric energy is promoted to high-voltage transmission to the transmission line. The advantages of thermal power generation are: low cost of early construction, stable power generation, uniform production throughout the year, so the power production in all countries in the world occupies the main position, generally around 70%. The disadvantages of thermal power generation are: the coal, oil and gas are non renewable resources, although the reserves are more, it will always be exhausted, and the pollution is serious. On the one hand, is rich in coal resources, 21 other resources into oil, gas, chemical energy costs are high, our country power is mainly coal, oil, gas, chemical energy power restrictive development plan. 2, hydropower: hydropower generation is the use of circulating water resources, mainly the use of ladder handover, river gap advantages, in order to produce strong water power, for power generation, belongs to the type of ecological and environmental power generation. The biggest advantages of water and electricity are: environmental protection, low cost of power generation, strong peak regulation ability (can adjust the power generation according to the load at any time). The disadvantage of hydropower is the high cost of construction, long time, uneven annual power generation, so the general hydropower power generation can only account for about 30% of the total and below. According to the layout of hydraulic power station, the hydropower station can be divided into dam type, diversion type and mixed type. Mainly by the water retaining structures (dam), discharge buildings (or spillway gate), diversion buildings (or diversion tunnel, surge shaft and power plant (including) including Naomizu, booster station of four parts). 3, nuclear power: nuclear power plants only consume a small amount of nuclear fuel, can produce a large amount of electricity, the cost per kilowatt hour is lower than 20% of the thermal power plant. Nuclear power plants can also greatly reduce the amount of fuel transportation. For example, a 1 million kilowatts of power plant coal consumption per year million tons, and the same power nuclear power plant every year only thirty or forty tons of uranium fuel, transportation volume is 10 thousand times. Another advantage of nuclear power is clean, pollution-free, almost zero emissions. Replacing nuclear power with nuclear power is a major trend in the world. The disadvantage of nuclear power is the high cost of early construction, high technical requirements, and few failures at ordinary times. Once large faults (such as nuclear leakage) occur, it will be a devastating catastrophe. From the former Soviet Union in 1954 to be the world's first nuclear power plant in 1957, the United States built test began the world's first commercial nuclear power plants, the development of nuclear power industry has been for decades, the installed capacity and power generation capacity increased steadily. By the end of 2004, 31 countries in the world have built or are building nuclear power units, of which 440 units are running nuclear power units, 26 units under construction Taiwan. In 2004, the world issued 26186 kwh of electricity, accounting for 16% of the world's total electricity generation. Due to the different situation, the proportion of total electricity generation in different countries is different: the largest in France, 78.1% in South Korea, 19.9% in the United States, 29.3% in Japan, 19.4% in the United Kingdom, 29.3% in Japan, and 38% in India, 2.8%. One is the core technical issues (vulnerable to foreign control), the two is nuclear leakage issues, China's nuclear power generation has always been a conservative and restrictive development path, According to the plan, even by 2020, China's nuclear power accounts for only 40/0 of the total. 4, wind power are the advantages of environmental protection, the disadvantage is large area power is not stable, not the construction of large and medium-sized power plants, so wind power development is very slow, and now the national installed capacity less than 500 thousand kilowatts, the maximum power is only 750 kilowatts. Nuclear power related reports In 1985, China began to build the first nuclear power plant, Zhejiang Qinshan nuclear power plant, with capacity of 300 thousand KW, PWR type, designed, manufactured and constructed by itself, and imported part of the equipment. In December 15, 1991, the grid connected power generation, commercial operation in April 1, 1994, passed the national acceptance in July 1, 1995. At present, the two phase of the project is expanding two domestic 600 thousand KW nuclear power plant, and three phase project two imported from Canada heavy water reactor type 700 thousand KW nuclear power unit. Dayawan Shenzhen nuclear power plant in Guangdong is China's second large nuclear power plants, the introduction of British and French equipment, installation of two sets of 900 thousand kilowatts PWR nuclear power unit. In August 8, 1988, the first tank of concrete was poured, the first generating unit was flat grid power generation in August 31, 1993, and the commercial operation in February 1, 1994; unit two was operated commercially in May 6, 1994. At present, in the construction of the project are: Dayawan second nuclear power station Lingao nuclear power station installed four sets of PWR 1 million kilowatts of nuclear power units; Jiangsu Lianyungang nuclear power plant, two sets of 1 million kilowatts of nuclear power units by the introduction of Russia; Guangdong province plans to build third nuclear power plants, Yangjiang nuclear power plant, the installation of 6 sets of 1 million kilowatts of nuclear power unit. At present, the installed capacity of China's nuclear power accounts for only 0.76% of the total installed capacity in China, and the power generation accounts for only 1.2% of the total power generation. Related reports of wind power China's wind power resources is about 253 million kilowatts, the development capacity of 160 million kilowatts. At the end of 1998, nearly 20 wind farms were installed in China, with a total installed capacity of 223 thousand and 600 kw. At present, the country's largest and largest wind farm in Asia is Xinjiang Dabancheng wind farm, equipped with 300, 500, 600 kilowatts of wind turbines, a total of 111 units, with a total capacity of 57 thousand and 500 kilowatts. Inner Mongolia Huitengxile wind farm, with 42 sets of 600 kilowatts and 10 sets of 550 kilowatts of wind power units, the total capacity of 30 thousand and 700 kilowatts. Zhejiang coastal Cangshan wind power plant, equipped with 33 sets of 600 kilowatts of wind turbines, with a total capacity of 19 thousand and 800 kilowatts. At present, China's wind power installed capacity accounts for only 1/1000 of the exploitable amount of four, and has broad prospects for development. Geothermal power generation related reports Geothermal resources in China are also abundant, and the distribution is very wide. The first geothermal power station was built in Deng village, Guangdong County, Fengshun province in 1970. The unit capacity is 100 kw. From 1971 to 1975, 300 kW Geothermal Power Station was built in ash town of Ningxiang County, Hunan province. At present, the largest geothermal power plant in Tibet is Chinese Yangbajain geothermal power station, the total installed capacity of 25 thousand and 180 kilowatts, began construction in 1975, 1977, 1000 kilowatts power generation units, after continued construction of 7 sets of 3000 kilowatts and 1 sets of 3180 kilowatts of geothermal units, to 1992 completed. Tibet Naqu geothermal power plant is a United Nations Development Agency project, installed 3 units of 1000 kilowatts geothermal power plant, completed in 1992. Related reports on tidal power generation Chinese has more than 500 kilowatts of power point 191 tidal power tidal power station can be developed, the total installed capacity of 21 million 580 thousand kilowatts, the annual generating capacity of up to 61 billion 900 million kwh, mainly distributed in Hangzhou, Zhejiang Bay, Yangtze River north of Yueqing Bay area three. The first tidal power station in China was built in September 1959 in Zhejiang Sea tidal power station, installed 2 units of 60 kilowatts. The largest tidal power station in China is the tidal test power station of Wenling County, Zhejiang, with a total capacity of 3900 kW and a capacity of 500 kW for power generation in May 4, 1980. At present, Chinese has built 7 tidal power stations, the largest installed capacity of 5000 kilowatts and 3 wave experimental station 40 kilowatts. 2 pilot wave power station is being built, installed capacity of 200 kW and a 70 kW tidal power station. Related reports on solar power generation Chinese first high power solar power station was built in Inner Mongolia Bahrain Right Banner Guli ancient village, the power of 560 watts, put into operation in October 11, 1982. In Tibet, two 10 kW, 20 kW and 25 kW PV power plants have been built. Chinese largest solar energy power station was built at an altitude of 4300 meters Tibet Geji County, the total power of 10088 watts. A 35 thousand KW solar power station is planned to be built in Lhasa. Nine, China's electric power started In 1879, the famous American inventor, Edison, invented the electric light, and soon connected the mysterious electricity with human life. In 1890s, the three-phase AC transmission system was successfully developed, and replaced the DC transmission soon. It became a milestone in the development of power system, and sounded the clarion call of the industrial revolution. Guangxu five years at the beginning of April eight (May 28, 1879), the Shanghai Municipal Bureau of Electrical Engineer Bi Xiaopu, in a warehouse in Hongkou Zhapu Road, with a 7.46 kW steam engine driven self-excited DC generator, will send power light carbon arc lamp. This is the first lamp lit on the Chinese earth. In 1882, the British founded the first power plant in Shanghai, Nanjing, with a capacity of 12 kilowatts, which is China's first power plant in Shanghai. This station, pioneered the use of arc than the global North train station Paris power plant 7 years later, more than 6 months in London Huoerpeng elevated road plant late than New York Pearl Street power plant 2 months earlier, 1 years earlier than the St. Petersburg Russia power plant, electricity, one of the Chinese also belong to the earliest use of electricity the country. Chinese people started their own electrical business, about 1888. In July 23rd of that year, the viceroy Zhang Zhidong from foreign purchases of 1 generators and 100 electric lamps, installed in the Yamen beside the Yamen for lighting. In 1890, some bureaucrats and wealthy families in Shanghai began to use incandescent lighting. In the early twentieth Century, the first wave of power development in China appeared. 1903 Jiangsu Zhenjiang big shine light company founded. In 1905 the Chinese Electric Company Limited was founded in beijing. The Chinese people in Tianjin, Shanghai, Ji'nan, Hankou, Chongqing and other places have also started the electric power industry. In 1904, under the Japanese colonial rule, Taiwan was built as the earliest hydropower station in China, with a installed capacity of 600 kilowatts. Yunnan Shilong dam hydropower station was built in 1912, and the first 22 thousand volt transmission line appeared in china. Because of the war, the electricity in old China has been developing slowly. Ten. Electric power development in New China Power industry known as the national economy "first officer" name. More than 50 years since the founding of new China, the electric power industry has developed rapidly. Since 1996, China's electricity installed capacity, electricity generation and electricity consumption have remained the second place in the world, second only to the United states. According to statistics, in 1949, the national power installed capacity of only 1 million 850 thousand kilowatts, the annual power generation capacity of 4 billion 300 million kwh, respectively ranked twenty-first and 25 in the world. After the founding of new China, the electric power industry in China developed rapidly. By 1978, the installed capacity of China's electric power has reached 57 million 120 thousand kilowatts, an increase of nearly 30 times than in 1949; the annual power generation of 256 billion 600 million kwh, an increase of nearly 59 times. After the reform and opening up, China's power industry continuous to two steps: in 1987, the power installed capacity of 100 million kilowatts, in 1995 2000 exceeded 200 million kilowatts, exceeded 300 million kilowatts, 400 million kilowatts in 2003 to 2005, exceeded 500 million kilowatts (including hydropower installed capacity reached 100 million kilowatts), 2006 exceeded 600 million kilowatts, exceeded 700 million kilowatts in 2007 in 2008, nearly 800 million kilowatts. In 1988, the total electricity consumption was 535 billion 800 million kwh, exceeding 1 trillion kwh in 1996, exceeding 2 trillion kwh in 2004, and reaching 34268 kwh in 2008. The rapid growth period of installed capacity is 2004 - 2008, the rapid growth period of the whole society electricity consumption is 2003 - 2007, the most installed capacity is in 2006, more than 100 million, more than twenty percent of the total installed capacity. The fastest growth in electricity consumption in the whole society was in 2007, an increase of 419 billion 800 million kwh compared with 2006, an increase of fifteen percent.

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