From the high reliability requirements of Tianjin urban distribution network should be used copper cable
The current discussion on the replacement of copper cables with aluminum cables has led to a lively discussion. Whether the aluminum alloy power cable can be applied in the field of urban distribution network, we through the Tianjin urban distribution network demonstration project, carried out the practice and demonstration as a guarantee of urban development, building a strong power grid is necessary, and for the construction of strong power grid, Safe and reliable and cost comparison, safe and reliable is always the first one.
Tianjin, as the largest coastal open city in northern China, has the reputation of "Pearl of the Bohai Pearl" and is an important transportation hub and major estuary in northern China.
After 2008, the annual growth rate of Tianjin economy has maintained double-digit growth, and once (2010-2013) accounted for the first national economic growth rate. In 2010, Tianjin's total economic output (GDP) and Shenzhen, Guangzhou, the gap was only 27.848 billion yuan, 98.45 billion yuan.
By 2020, Tianjin will build into an economic prosperity, social civilization, science and education developed, well-equipped, beautiful environment of the international port city, the northern economic center and eco-city. Regional economic fast, high-quality development and people's yearning for a better life, the development of Tianjin power grid put forward higher requirements.
In order to adapt to the new situation of Tianjin city upgrading and development, the State Grid Tianjin Electric Power Company fully implemented the world-class city power supply network development action plan & rdquo; .
State Grid Tianjin Electric Power extensive research at home and abroad advanced urban power grid development level, aimed at Singapore, Paris and other international advanced cities, comprehensive coverage of all aspects of power grid characteristics to determine the power supply reliability rate of 99.999%, customer satisfaction, Total assets yield 3.6%, clean energy consumption rate of 100%, the proportion of interactive users 70% & rdquo; world-class level five-dimensional index system.
Power supply reliability rate of 99.999%, is a very high target, domestic survey shows that by the end of 2014, the State Grid Corporation of the city with a total of 270,000 km power cables distribution network, the cable rate of 47.1%. In the transport of cables to copper-based cable, the proportion of aluminum core cable is low, less than 5%. Zhejiang University, the proportion of aluminum core cable is relatively large, most of the second half of 2009 after the start of operation, according to the operation record of about three years, a total of aluminum core cable failure occurred 29 times. The failure occurred mainly in the cable accessories, especially the middle connector occurred 19 times, accounting for 65.52% of the failure, the middle connector failure in addition to an external force damage, the remaining 18 times are breakdown breakdown; other 10 times were cable terminal failure, External force damage or poor construction and other reasons, aluminum cable failure 500mm2 cable failure is particularly prominent, a total of 18 times, accounting for 62.07% of the total statistical failure, of which 14 times for the cable intermediate connector insulation breakdown or explosion, accounting for the middle of the cable 78.8% of the joint failure.
It is understood that the current large-section aluminum core cable joint construction technology has not yet fully solve the reliable, stable, mature on-site crimping technical problems.
Aluminum alloy cable is only an improved aluminum cable, still belong to a kind of aluminum cable. This operation can not meet the high reliability requirements. And Zhejiang grid in recent years has been basically no longer use aluminum and aluminum alloy cable, aluminum cable has also been switched to copper cable.
Strong construction of the power grid is the most basic guarantee of urban development, is particularly important, therefore, whether it is Tianjin distribution network demonstration project, or all Tianjin urban distribution network, must all use copper cable. Aluminum or aluminum alloy cables should not be considered and selected.
1. Lessons from the Tianjin bombings
Tianjin this chemical explosion to get blood lessons. Urban construction and management can not have the slightest negligence and paralysis. Regardless of normative development, design, construction quality, operation and management, safety measures, contingency plans and other aspects should be strictly in a scientific way to ensure that the city's long-term stability. Copper cable and aluminum alloy cable How do we choose? Obviously the answer is clear.
2. lay the channel and space
At present, the more popular argument is in the similar energy consumption conditions, as long as the increase in aluminum alloy cable cross-section, you can achieve the copper cable electrical performance. In fact, in practice, the aluminum alloy cable is larger than the copper cable two cross-section specifications can reach similar carrying capacity. Increasing the conductor cross-sectional area poses new problems for cable laying, cable channel construction dimensions and electrical performance. Such as whether the cable trough needs to be expanded and redesigned? There is not enough space and so on.
3. Economy and Reliability
Safety and cost comparison, security is always the first one. All walks of life are so to sacrifice the cost of security in exchange for cost reduction is not desirable, the grid is even more so.
The biggest advantage of aluminum alloy cable is the purchase cost is lower than copper cable, can save investment. But the assessment of the project economy is not only the main investment and must be fully considered. For example, the increase in the size of the cable channel (cable wells, ditches, etc.) causes an increase in the additional costs. In the construction of urban distribution networks, the channel resources are often the most scarce and expensive.
Too close to make the current carrying capacity decreases as the cable spacing decreases; due to the increase in capacitance current corresponding to expand the arc suppression coil capacity, will result in increased investment costs. In addition, the maximum allowable short circuit temperature and thermal stability of the aluminum alloy cable is lower than that of the copper cable, and the corresponding adjustment will also increase the cost.
And then run the cost analysis. Aluminum or aluminum alloy cable loss is higher than the copper cable, the annual loss of electricity and more expensive. In the event of an accident, it will bring about a greater loss of life and production, the number of difficult to estimate, even beyond the economic losses. The high reliability requirements of the urban power grid, in addition to economic benefits, must also take into account the social impact. Often more social benefits than economic benefits. The
In summary. Aluminum alloy cable and did not like the propaganda made a revolutionary material progress, just compared with the aluminum cable, the performance has improved. Its increased cross-section and copper cable electrical performance similar to the argument, but also specific analysis, which brought many other new problems have not been fully demonstrated. I believe that aluminum alloy cable should have its use but not suitable for urban distribution network.