Introduction: under the current situation of great changes in the global energy pattern and the continuous entry of China’s power reform into the deep water area, under the new pattern of energy development dominated by clean energy and centered on electricity, the power grid is becoming the main carrier of energy allocation.
State Grid: from the overall development of the world power grid, what is the development direction of the distribution network in the future?
Ma Zhao: in the current situation of great changes in the global energy pattern and the continuous entry of China’s power reform into the deep water area, under the new pattern of energy development dominated by clean energy and centered on electricity, the power grid is becoming the main carrier of energy allocation.
In particular, distribution network, which directly connects Distributed Renewable Energy and active flexible loads and users, is not only the physical carrier and cornerstone of smart grid, the main source of data required by relevant new technologies, but also an indispensable and important role of the next generation integrated energy system, so it has attracted much attention.
Providing safe, reliable, efficient, green and interactive electric energy service is the fundamental responsibility and goal of distribution network. With the gradual penetration of Distributed Renewable Energy and new flexible load with the integration of generation, utilization and storage, modern distribution network has the characteristics of discreteness, dynamics, nonlinearity, multi-objective and uncertainty, and has become a typical complex large-scale system.
In the future, the distribution system will meet the large-scale intervention of distributed renewable power sources and energy storage devices, adapt to the plug and play of new loads such as electric vehicles, and meet the advanced needs of users for power quality and information interaction.
The core value of the energy revolution is first green and low-carbon, followed by energy conservation and efficiency. Finally, we should achieve the goal of an energy-saving society. In terms of energy supply, it is multi supply and multi wheel drive. In order to solve these problems faced by the power system, the application of energy Internet came into being. Visionary and courageous pioneers have begun to explore innovative technologies and business models of energy Internet.
In my opinion, the future urban distribution network will gradually evolve into an integrated energy service system. Its special attributes are systematicness, universality, inclusiveness, openness and interaction. Its special attributes in technical characteristics are measurement digitization, control networking, state visualization, function integration and information interaction.
What characteristics will the distribution network have in the future?
Ma Zhao: personally, I think the future distribution network should have the following characteristics:
First, renewable energy will gradually become the main primary energy source in the power grid. Fossil energy will be exhausted day by day. Renewable energy is a green energy for sustainable development and is becoming the second largest source of electricity in the world.
Second, the structure and operation mode of distribution network will change significantly. In the future, the structure of power grid will show the coexistence of large power grid and micro grid.
Third, a highly integrated physical power grid and information physical system. Changing the structure and operation mode of power grid, improving the performance of electrical equipment and adopting new functional electrical equipment are more fundamental methods to solve the problem of power grid in the future.
The development of power equipment and protection equipment with adaptive function can significantly reduce the technical requirements of power grid for sensing, communication and data processing. This is very beneficial to improve the safety, reliability and comprehensive benefits of power grid.
Fourth, the development of a new power market and business model – energy Internet. The development trend of distribution network in the future will be integrated energy Internet. Thousands of power supply points connected with users will realize the balance of output and load of the whole system with the precise step of differentiation under the bidirectional constraints of demand and price rules. To realize the real-time balance of power generation and consumption, power market and business model are very important.
Fifth, new materials and technologies will be widely used in the future distribution network. High voltage and high-power power electronic devices and equipment, as well as the invention and use of new high-performance electrodes, energy storage, dielectrics and hydrogen storage materials; There are also other new materials, such as nanocomposites, nonlinear dielectric materials for field (including electric field and magnetic field) control and temperature control, new insulating materials, insulator metal phase change materials, new ferromagnetic materials, power sensor materials for high efficiency and low energy consumption, etc.
The application of new materials and technologies will simplify the structure and control of the power grid, optimize the operation of the power grid, and respond to power fluctuations and power grid faults.
Compared with the developed countries in the world, in what aspects does China’s distribution network development need to make efforts?
Ma Zhao: considering the current situation of distribution network at home and abroad, especially the gap between China’s distribution network and the international advanced level, I personally think that the following aspects should be considered in building a world-class distribution network in China:
Social and economic macro comparison. The state of social and economic development directly reflects and guides the planning and construction of distribution network. Some comprehensive data on China’s new urbanization construction and per capita annual domestic power consumption show that there is a large space for the level of urbanization and electrification in China. Accordingly, there is still great potential for urban distribution network planning, construction and large-scale development.
Power supply reliability. Taking 2014 as an example, the average power supply reliability rate of 10kV users in China is 99.940%, and the average outage time is 5.22 hours / household.
Among them, the average power supply reliability rate of urban (Downtown + urban + urban) users is 99.971%, and the annual average power outage time is 2.59 hours / household; The average power supply reliability rate of rural users is 99.935%, and the annual average outage time is 5.72 hours / household.
Compared with the international advanced level, the power supply reliability rate of Singapore reached 99.999941% in 2011, and the average outage time was 0.31 minutes; In 2009, the reliability rate of power supply in Tokyo, Japan reached 99.999619%, and the average outage time was 2 minutes.
Therefore, it can be seen that there is much room and pressure to improve the reliability of power supply in China.
Distribution network structure. The structure of distribution network determines the reliability and flexibility of network operation. In this regard, different countries have formed different design methods.
Taking the urban distribution network as an example, the cable network in Paris adopts T-connection of three ring network or T-connection of double ring network; London cable network adopts multi branch and multi contact wiring mode; The 22 kV cable network in Tokyo adopts the main line standby line, ring and point network wiring mode, the 6 kV overhead network adopts the multi segment and multi contact mode, and the cable network adopts the multi segment and multi contact mode; Singapore cable network adopts “petal type”, that is, closed wiring of ring network.
Although the specific topologies are different, the basic trend of foreign advanced grid structures is to show “dumbbell” development, and the core principle is to “strengthen both ends and simplify the middle”, which not only ensures reliability and safety, but also avoids repeated construction.
At present, China’s Beijing high-voltage distribution network is similar to the international advanced distribution network, mainly with ring network and radial operation (i.e. “hand-in-hand” grid structure). However, the pressure distribution network has a large promotion space, the power grid structure is relatively weak, and the network wiring mode is complex, which is difficult to form standardization.
In addition, the insulation rate of 10 (20) kV urban network overhead lines at the advanced level abroad is more than 80%, while at present, it is only 22.4% in China. Therefore, in terms of distribution network structure upgrading, a major task at present is to learn from foreign advanced level and make adjustments in line with local development reality.
Specifically, for first tier cities, strive to build a reliable and flexible network architecture, fully realize the bilateral power supply and ring network structure, strengthen the connection rate of medium voltage lines and improve the load transfer capacity; For other cities and towns, in combination with local economic and load development, we should first solve the problems of insufficient n-1 capacity of high-voltage distribution network and “single line single transformer”, and gradually improve the problems of insufficient segmentation of medium voltage distribution network and insufficient line connection; Rural areas should first improve the power supply radius.
Distribution network automation level. In 2014, the overall coverage of distribution automation within the scope of State Grid Corporation of China was 20%, and the coverage of smart meters was 60%. The automation coverage rate in Japan is almost 100% and that in France is 90%.
In terms of the actual situation, some first tier cities in China have initially realized the considerable and controllable distribution network, and the operation monitoring and automatic control capabilities of other regions are insufficient, so there is still the potential and task of substantial improvement.
Specifically, in terms of infrastructure construction, first tier cities should focus on improving the construction of medium and low-voltage optical fibers and other communication networks; Other regions should strengthen the construction of high and medium voltage communication infrastructure, and cooperate with the appropriate development of different levels of automation equipment.
Distribution network asset management. The integration of new and old equipment and old and new technology networks of distribution network is the physical carrier of the future integrated energy system and the indispensable cornerstone and support for the construction of smart grid and energy Internet.
Therefore, comprehensively and systematically mastering the health level of existing distribution network equipment and network should be the starting point of lean and efficient management of distribution network assets.
From the perspective of foreign development process, when the growth of economy and power load basically reaches stability, the guarantee for distribution network enterprises to realize social responsibility, reasonably control the power grid and improve profitability is asset management technology.
How to make efficient use of existing equipment and networks is one of the two major directions of the international power grid organization. In particular, with the retirement of experienced engineers and technicians, there is a fault and lack of succession of talents, and there is a crisis in the inheritance of rich first-hand experience and professional knowledge, which has attracted global attention, especially the high vigilance of western developed countries.
Taking the UK distribution network as an example, since the 1970s, the UK has tried to scientifically manage a large number of assets of the distribution network, and its asset management system is even earlier than the Internet technology based on IPv4.
At present, after long-term practice, the UK distribution network has formed a lot of advanced experience in technical specifications, software and hardware platform R & D and application. In contrast, the concept and technology of domestic asset management started late. The technology and level of asset management still need to be greatly improved.
In view of the characteristics of large quantity and wide range of distribution equipment, relatively low monomer price and complex and changeable distribution network structure, we should deepen the research and development of asset management theory / application system suitable for China’s national conditions and distribution network management and control mode as soon as possible, and carry out pilot work in depth, so as to promote and apply the beneficial scheme.
The State Grid Corporation of China also carried out the international benchmarking of distribution network assets last year, and I myself participated in some work as an expert. I think it is particularly necessary to change the concept and deeply understand that scientific and intelligent asset management is an effective way to improve quality and efficiency. Asset management is not a simple management work, but a systematic and comprehensive discipline integrating a variety of theories, technologies and experiences, and coordinating technology, economy and management. It is an art of balancing cost, performance and risk.
In the future, the integrated energy Internet will also put forward higher requirements for distribution network asset management. Technologies oriented towards energy information physical system, big data, deep machine learning and artificial intelligence application will provide scientific and practical methods and tools for asset management.
What is the future development direction of the power system of the State Grid?
Ma Zhao: electric power has the characteristics of efficient and fast transmission, high energy conversion efficiency and convenience in terminal energy consumption, which determines that the power grid will become the resource allocation center in the future comprehensive energy system and the new belt and core to realize energy interconnection and comprehensive utilization of energy.
Starting from the energy consumption terminal, we should strive to promote the construction of comprehensive energy system and gradually build a regional comprehensive energy system from the active distribution system, including new business forms and models such as distributed energy, energy storage and intelligent microgrid.
Smart grid is the basic support platform and resource allocation center of integrated energy system. Multi energy collaborative optimization is the only way for large-scale application of integrated energy. We should accelerate the integration of diversified energy and build an energy Internet with interactive supply and demand. In terms of energy Internet planning technology and architecture design, the characteristics of smart grid can be improved by integrating a variety of energy networks and energy storage.
We must vigorously study the integrated planning method of comprehensive energy and intelligent buildings, realize the optimal allocation of energy, energy storage and load in intelligent buildings, realize the integrated and optimal operation of multiple energy systems, and build a sustainable zero net energy consumption community.
Therefore, I suggest to implement the integrated energy planning of smart city with multi network integration in the context of big data, establish probability and risk assessment models, and gradually realize the optimal planning with multiple objectives; Strengthen diversified energy supply, multi wheel drive and load dynamic interaction, take the Internet and big data as the core and power electronics and other technologies as the support, carry out standardized module design, establish a more flexible network topology, and finally realize intelligent energy consumption and build an energy-saving society.