Guide: From the analysis of major blackout accidents in the world for nearly half a century, those areas of the power grid/power capacity are too large, and freely connected. When there is a fault, the chain reaction will cause a major power outage due to the entire AC network. China has a lot of installed capacity, but after DC partitioning, the area of ​​each area is not large, forming a strong load center, more dispersed external power supply, and not free networking, the result is very safe.
1. Reasonable power transmission scale of the power grid1. The huge Sanhua exchange UHV network will surely embark on the world's major blackouts
Since 1965, there have been 25 major power outages in the world (each load loss ≥ 8 million kilowatts), 20 of which were caused by the huge network of free exchanges, and the largest power outage in the United States at the time was the largest in the world (6 times). The most serious (load loss accounted for 29.6% of the total). Known as the technologically advanced US/Canada/European Union, 14 times, the number of times and load loss accounted for 56% and 54.2% respectively. From the cause analysis, most of the major power outages occurred in the AC grid structure with large regional and power capacity and large network.
China's power capacity now ranks first in the world. Why, apart from Taiwan, why has there never been a major blackout? For more than 30 years, according to the current "Power System Safety and Stability Guidelines", six large-area sub-areas have been established. The main area is DC-connected, which completely prevents major blackouts and becomes the safest and most reliable power grid structure in the world.
From the analysis of major blackout accidents in the world for nearly half a century, those areas of the power grid/power capacity are too large, and they are freely connected. When there is a fault, the chain reaction will cause a major power outage due to the entire AC network. China has a lot of installed capacity, but after DC partitioning, the area of ​​each area is not large, forming a strong load center, more dispersed external power supply, and not free networking, the result is very safe.
2. The size of the “Sanhua†regional network is not in line with the reasonable scale of power grid.
<Sanhua Network> From Table 1, it is proved that the installed network/grid range/free networking method in the network is equivalent to the countries with major blackouts in the world, and it is on the unsafe road of major blackouts such as North America; especially the more dangerous is the exchange of national network applications. UHV is more insecure and wasteful than the existing ultra-high pressure in the world, such as the United States, and the consequences are even more serious.
The exchange of UHV transmissions that have been used in the world for decades to determine the application of <Sanhua Network> is not a viable failure technique. However, the State Grid Corporation has always conflated the "transportation of UHV" with the "DC UHV" and masked the "failure technology" of UHV with the "progressive technology" of DC.
In the last century, Europe, the United States, Russia and Japan studied the failure of "transmission of UHV transmission" for "long-distance transmission", but studied the success of "DC transmission". In the former Soviet Union, in order to realize the long-distance (1905 km) transmission of 1200 kV, starting from 1972, in the 9-year operation of 1985-1994, the overvoltage problem was serious, and 100% compensated shunt reactors had to be installed on the line, most It can only send 1.6 million kilowatts. Practice has proved that the former Soviet Union has not been able to solve its technical risks for 22 years, and its power transmission capacity is poor. It is extremely wasteful of investment and has to be depressurized for 500kV forever.
Tokyo Electric Power Co., Ltd. built a total of 426 kilometers of AC 1000kV lines from 1992 to 1999, but it has not built a substation and can only operate at 500kV. State Grid Corporation’s Beidaihe UHV Transmission Technology Seminar in 2005 stated: “According to Tokyo Electric Power’s forecast, it is necessary to boost the operation of the Nanyanmu UHV main line during 2010â€. When Mongolian participated in the meeting of the International Power Grid Committee in Osaka, Japan at the end of 2007, the answer from Tokyo Electric Power was “to accept the lesson and never to step upâ€. However, State Grid Corporation still promotes Japan's boost operation in 2015, and now it is 2015, it is really deceptive propaganda.
In order to "long-distance transmission", Europe, the United States and Japan are studying "AC high-voltage" and also studying "DC transmission", successfully applying thyristor instead of mercury rectifier, which has achieved the goal of "long-distance transmission" safely and economically. Naturally, the "AC UHV" was eliminated. China's direct current transmission is developing rapidly, and DC isolation is also divided into six major exchange areas, ensuring that China has become the safest country in the world where no major blackouts have occurred. Therefore, it is necessary to recognize that the exchange of UHV is not "advanced technology" at all, but rather the "failure technology" that has been tested/runned by many countries.
In 2005, the United Nations Department of Economic and Social Affairs published a report in New York: "The exchange of 1200kV was used in the long lines of Siberia in Russia. In any case, beyond 1000kV, the actual difficulty, equipment and insulation that can withstand such high voltage are too high. Difficult to adopt." The United Nations document refers to two risks: one is the technical difficulty risk, and the other is the economic cost risk. This is the conclusion that the world has failed to distinguish the UHV from the technical economy.
The UN document also pointed out: "The long-distance transmission application of DC, compared with AC, more than 600 kilometers are the economic distance of DC transmission, and DC transmission is safer and more reliable." The UN document also pointed out that different AC grids can avoid many technical problems arising from the operation of the synchronization network itself through DC networking. It also cited the power outage accident in the United States and Canada in 2003. The failure of any one of them affected the entire AC synchronous network. The larger the synchronous network, the longer the line, the more serious the voltage collapse and stability were, and the more likely the chain reaction was blackout.
As a result of the conscientious implementation of the "Steady Guidelines", China Southern Power Grid reported the conclusions of the "China Southern Power Grid 2013-2020 Planning Research Report" at the Southern Network "Twelfth Five-Year Plan" Review Meeting held by the Energy Bureau in July 2013: "South In the future, the development of power grids will mainly adopt DC transmission technology. At the same time, after the 12th Five-Year Plan period, the communication sections of the inter-provincial power grids will no longer be strengthened. The South China Power Grid will be gradually decomposed into 2~3 based on the provincial power grid. Synchronous grid bureaus." The conclusion that the South Network is divided into two or three districts is only discussed one day and the experts have unanimously approved it. China Southern Power Grid Corporation decided not to use "AC UHV", and the long-distance transmission fully utilized the function of "DC UHV" transmission. It is also a wise decision to divide DC into 2 or 3 districts, and it will meet in March this year. Menggong once suggested that Guangdong should also be separated into two east and west communities by DC to solve the problem of short-circuit current exceeding the standard of power supply development and the safety problem of more West-East power transmission to Guangdong in the future.
2. Research on the security of "Sanhua" regional network1. "Sanhua Exchange UHV Networking" has to violate the "Stability Guide" for far-distance transmission and constitutes numerous 1000/500kV <electromagnetic ring network>, which is even more unsafe.
In the end, can the transmission capacity of UHV lines reach 5 million kilowatts? If only a single return line is required to follow the guideline to expedite a single-phase transient fault, the close distance of 300 km is barely achieved. The three-way network planning is all the same double-circuit line of the same tower. According to the regulations, it is necessary to maintain the stability after a tripline fault trip, and 300 kilometers can not be reached.
Sanhua Network is more than 2,000 kilometers. It must be supported by 500kV network every 300 kilometers. It can only be transmitted far away. As a result, it has to violate the current "Stability Guide" of the "Stratification", which constitutes numerous 1000/500kV electromagnetic ring networks. However, it is still not possible to send more power, because once the 1000kV line fails, the original transmission power is transferred to the 500kV power grid, and a slightly larger power will cause a stable damage accident.
The worst serious accident in China's history on July 1, 2006 was that the two 500kV lines were tripped due to protection misoperation, and 1.78 million kilowatts of power was transferred to the 220kV network through 500/220kV <electromagnetic ring network> to cause stable damage. It is a violation of the "Guidelines" to form an electromagnetic ring network. After the accident, the State Grid had to untie the ring network in Central China. Knowing that the electromagnetic ring network violates the "Guidelines", in order to promote the exchange of ultra-high voltage, it still misuses dozens of 1000/500kV <electromagnetic ring network>, which is not only extremely wasteful, but also can send 3 million kilowatts on average, still forever To the 5 million kilowatts of transportation capacity that the State Grid Corporation has consistently promoted, the more serious is the hidden danger of dozens of major blackout disasters.
2. Sanhua should not be connected to the Internet. All major districts should conscientiously implement the "Steady Guidelines" to make safe and economic decisions for the development of the power grid.
The practice of world history proves that there is a "three-point" structure of "stratification" (zoning) <distributed external power supply" established in accordance with China's "Guidelines for Stability" to prevent major blackouts. The implementation of the Sanhua Network by the exchange of UHV completely destroys the established “three-point†structure and becomes more dangerous than the North American European grid structure that experienced major power outages. Violation of the "Stability Guide" and the application of "simulation" can not judge its security for such a complicated power grid; the conclusions judged by "N-1/Part N-2 simulation" are false.
In 2005, the United Nations Department of Economic and Social Affairs published a report in New York: "The exchange of 1200kV was used in the long lines of Siberia in Russia. In any case, beyond 1000kV, the actual difficulty, equipment and insulation that can withstand such high voltage are too high. Difficult to adopt." The United Nations document refers to two risks: one is the technical difficulty risk, and the other is the economic cost risk. This is the conclusion that the world has failed to distinguish the UHV from the technical economy.
The UN document also pointed out: "The long-distance transmission application of DC, compared with AC, more than 600 kilometers are the economic distance of DC transmission, and DC transmission is safer and more reliable." The UN document also pointed out that different AC grids can avoid many technical problems arising from the operation of the synchronization network itself through DC networking. It also cited the power outage accident in the United States and Canada in 2003. The failure of any one of them affected the entire AC synchronous network. The larger the synchronous network, the longer the line, the more serious the voltage collapse and stability were, and the more likely the chain reaction was blackout.
China Southern Power Grid Corporation decided not to adopt "AC UHV", and the long-distance transmission fully utilized the "DC UHV" transmission function, which is the wise decision.
3. Can the complex “Sanhua Networking†rely on “simulation calculation†to ensure safety?
Academician Pan Jiaxuan once quoted Academician Lu Qiang as a reporter for the safety and stability of the "Three China Network": "We conducted a simulation test of five or six hundred cases. The answer is: the safety and stability of such a power grid is Guaranteed." Even if the branch components of Sanhua Network are 500-600, this is only equivalent to the calculation condition of one component fault trip (called N-1), such as two-component chain trip (N-2). Conditions, you have to do:
(500 to 600) 2 = 250,000 to 360,000 cases of simulation test.
In the past decades, it has been proved that the unstable oscillation of pets and free networks is not caused by N-1 or N-2. For example, in 2003, the US and Canada experienced a power outage and experienced N-14. In 1965, the blackout in New York experienced N-5, 1996. In July and August of the year, the two major blackouts in the western United States experienced N-11 and N-15 respectively, which caused the whole network to oscillate.
We checked the report of the “Research on the Construction of the Receiving Power Grid†of the Electric Power Research Institute in June 2010. After experiencing the N-1 or a very small number of N-2 simulation calculations, it is impossible to use the simple calculation as a safety basis because of the free network structure and special It is more dangerous than ultra-high pressure. The instability of the UHV Sanhua network is difficult to analyze and evaluate, and it is difficult to prevent and difficult to save.
The practice of world history proves that there is a "three-point" structure of "stratification" (zoning) <distributed external power supply" established in accordance with China's "Guidelines for Safety and Stability of Power Systems" to prevent major blackouts. The implementation of the Sanhua Network by the exchange of UHV completely destroys the established “three-point†structure and becomes more dangerous than the North American European grid structure that experienced major power outages. Violation of the "Stability Guide" and the application of "simulation" can not judge its security for such a complicated power grid; the conclusions judged by "N-1/Part N-2 simulation" are false.
4. Sanhua should not only be connected to the Internet. According to the "Steady Guidelines", DCs should be used in all major regions to be the safest and most economical way in the future.
Just in May 2013 in Shanghai, “East China's Four Provinces and One City National Economy and Power Development Planning Seminarâ€, Meng Dingzhong proposed the East China Division for the State Grid Corporation (East China Exchange UHV Network).
(1) Studying a reasonable grid structure from Huadong 2015/2020 power/load planning
According to the three reports of State Grid Corporation's December 2012 and May 2013 “East China “Twelfth Five-Year†Power Grid Development Planâ€, from 2015/2020, the load requirements and power planning of the provinces and cities in East China will prove that all provinces and cities, including Anhui, in the future. The province is short of electricity, how to solve it? First, continue to rely on remote DC transmission, and second, build new power sources near the urban load centers, each of which has a basic balance of power supply/load, and does not require large-scale power transmission between each other. The existing 500kV power grid has met the requirements and does not need to be exchanged at all. High voltage networking. In order to solve the problem of excessive short-circuit current exceeding the standard and the safety problem of ensuring more DC feed, the most cost-effective, safe and reliable method is to implement the "Stability Guide" and use DC to gradually asynchronousize the East China Power Grid (Isolation). The interconnection is divided into four partitions. Accidents in different districts do not affect each other, and it is even more unlikely that instability/voltage collapse/disintegration accidents will occur at the same time. Table 2 lists the first is to continue to rely on remote DC transmission, and the second is to build a new power supply near the urban load center, which can fully make the basic balance of power supply/load in each province and city, and determine the feasibility and necessity of dividing East China into four regional power grids.
(2) Development plan of East China Power Grid
How should the East China Power Grid develop? According to the plan of the State Grid Corporation, it is necessary to waste 74 billion yuan of investment and cover an exchange of UHV power grids. Therefore, the Anhui output that is not necessary from coal-fired power grids for a short period of time accounts for 2.2% of the entire network, which is a serious waste. For example, in the future, DC will be divided into four major regions, and the power load of each district will be basically balanced. The interval current is not large. The original 500kV power grid is sufficient for application. The completed AC UHV facility has no electricity to send, and even violates the guidance of the “Partition†function. Obsolete. After the partitioning, all 500kV AC lines are transmitted by medium and short distances. This is the most reliable, effective and economical solution to the security and stability of the whole network.
(3) Analysis of the basic conditions and feasibility of East China (Division)
[a] When partitioning by DC, after considering the partition, each zone maintains a certain short-circuit current level (about 50 kA). The main purpose is to provide a fairly urgent reactive reserve for the grid in the event of an accident, which is especially suitable for DC receiving. After the partition, the short-circuit current is not expected to be too low, so 500kV transformers, series reactors, short-circuit current limiters, etc., which increase the short-circuit impedance, should not be purchased specially, because once they are partitioned, they all have a negative effect, which is equivalent to being invalidated.
[b] When partitioning by DC, after considering the partition, once the DC blocking of the largest capacity is stopped, the lost power is offset by the back-to-back support of other DCs and zones in the zone, and the value should not exceed the original power supply. %. Considering that the largest 11 million kilowatts of DC each 1/2 falls in different zones, it is more reliable to meet the above requirements.
According to Table 2, Shanghai and Zhejiang are combined into one district to meet the requirements. Therefore, it is recommended that East China Power Grid will provide research in four districts: <Zhejiang/Shanghai><Jiangsu><Anhui><Fujian>.
[a] The first is to apply DC back-to-back partitions
The [Northwest-Huazhong] [Northeast-North China] and [China-Russia] Heihe Rivers, which have already been applied in China, are reliable in back-to-back operation and have good zoning functions. Figure 1 is based on the peak summer 2012 peak summer tide/2013 winter peak trend (from the State Grid report) to study the position and capacity of DC back-to-back. With the development of power supply/load, all provinces and cities should have less tidal currents. To choose its capacity.
Figure 1: Power flow and back-to-back zoning conditions in five cities in East China (7 DC back-to-back total of 7.75 million kW)
[b] The second is to apply DC-powered inverter stations to implement partitioning (Figure 2, 3)
For example, Zhejiang Wuyi Inverter Station, which accepts Xiluodu DC long-distance transmission, will receive power in two parts according to the power required by Zhejiang/Fujian in the future, that is, to achieve the purpose of “Division†(the existing Ningshuang two-way 500kV exchange line is appropriately changed to Back-to-back operation), because in the future both provinces are short of electricity, without the need for more investment, you can get the "zone" safety / economic effects.
In the future, the total investment of DC division into four major divisions will not exceed 6.2 billion yuan, which is one-twelfth (8.3%) of the static investment of UHV network (74.4 billion yuan) in East China. It is economical and safe to operate. reliable.
(4) <Partition> to ensure safe operation of multiple DC feeds
In the future, after East China is divided into four regions by DC, DC is fed into each zone, and any zone is faulty. Only when the protection is rejected and the long-term (compared with the DC low-voltage protection time setting) voltage collapse (and DC low voltage) In the case of a protected voltage setting comparison, it is theoretically (practically impossible) to trip the DC in the zone. However, the DC isolated neighboring area is not affected by the voltage collapse, so DC transmission is more secure after DC partitioning.
(5) <Division> completely solve the problem of short-circuit current exceeding the standard
In the future, the East China 500kV power grid will be able to completely solve the problem of short-circuit current exceeding the standard according to the "Stability Guide" (divided into four major districts). All districts maintain a safety level of 40-50 kA; 50 kA breakers (especially GIS) do not. Need to replace it with 63 kA. The reactors, current limiters, and transformer impedances that were originally installed to limit the short-circuit current are no longer needed, and if they are installed, they have a negative effect on the operation.
(6) In the future, the “Division†will ensure that the East China Power Grid is fully realized.
The 500kV power grid must be covered with a large number of 1000/500kV electromagnetic ring networks to transmit power. Violation of the "Steady Guide" (stratification) will inevitably lead to major power outages. The voltage layer of East China Power Grid is 500/220/110/35/10(20)kV, and the power grid below 110 kV has fully realized the stratification. After the four major regions, the 500/220kV grid can be made from 'most of'. <Layered> improved to 'complete' (stratified) to avoid serious electromagnetic ring network accidents in China.
(7) Reforming/optimizing the power supply layout of various districts in East China according to the “Standards for Stabilization†(Distributed External Power Supply)
After the partition in the future, the load centers of each area will form a 500kV ring network. The power supply to the ring network, whether it is the power supply in the area or the AC/DC power supply from a distant place, should be based on the "distributed external power supply", commonly known as "point pairing". The power transmission mode of the network completely avoids the danger that the multi-point parallel/ring power transmission will completely stop the load during the fault; once the fault trips, the integrated loss power supply should not exceed 6% of the total load of the receiving end. It will not affect the operation. This is not only the provisions of the Stabilization Guide, but also the experience of domestic and foreign accidents for more than 30 years.
ConclusionFrom the analysis of major blackouts in the world, major blackouts have occurred in the AC grid structure with large regional and power capacity and large network. The scale of Sanhua UHV AC network is equivalent to that of power grids in countries where major power outages have occurred. It is never feasible to use the unsafe and uneconomical exchange of UHV, which has long been abandoned in the world, to be more unreasonable.
Sanhua should not only be connected to the Internet. According to the "Standards for Stability", DCs should be used in all major regions to be the safest and most economical way in the future. In my report, I have suggested that the East China Power Grid should be divided into four major divisions by DC isolation. The total investment is no more than 6.2 billion yuan, which is one-twelfth (8.3%) of the static investment of the East China Exchange UHV network (74.4 billion yuan). It is economical and safe to operate.
In order to realize the "three high-speed Internet connection", the State Grid Corporation does not allow for democratic and objective argumentation analysis from all aspects of science and technology/economics, and hides the inherent defects of the UHV with the superiority/feasibility of UHV DC. Because of the realization of the power "monopoly" with Sanhua Network, it violated the spirit of "breaking monopoly and introducing competition" in the State Council Document No. 5 of 2002 on the reform of the power system.
In view of the fact that this is related to the long-term strategic and security layout of the country's energy, it is hoped that the government departments must attach great importance to it. If it is not in accordance with the state's prescribed approval procedures, it will not be fully demonstrated by experts from different perspectives according to the scientific development concept, and democratic discussions will be approved. The exchange of UHV networking projects continues to take a step forward, not only to conceal serious security risks, but also to cause a major loss to the national economy. We should continue to implement the "Power System Safety and Stability Guidelines", which has played an important role in China's power grid security for 30 years, and make careful decisions to avoid irreparable "three-way exchanges and high-voltage networks" caused by mistakes in decision-making. 100 million yuan of national property losses.
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