The economic and social development has increased the voltage level of the power system and increased the complexity of the power grid, posing great challenges to the safe and stable operation of the power system. As the first line of defense in the "three lines of defense" to ensure the safe and stable operation of the power system, the relay protection is also facing a severe test. It is increasingly difficult to adjust the traditional protection. With the development of the smart grid construction of the State Grid Corporation, the technologies of network reconfiguration, distributed power access, and microgrid operation brought by the characteristics of the smart grid have put forward new requirements for relay protection, based on local measurement information and a small amount. The conventional protection of regional information faces great difficulties in solving these problems. At the same time, the research and application of new technologies (such as new sensor technology, clock synchronization and data synchronization technology, computer technology, optical fiber communication technology, etc.) also provide relay protection. The development provides a broad space for development. Under the promotion of the above factors, based on the wide-area measurement information, the wide-area relay protection considering the design and configuration of relay protection from the perspective of the system has received more and more attention. As early as 1997, Swedish scholar BerTIl Ingel ssON proposed the concept of wide-area protection to prevent long-term voltage collapse and other control functions. The International Conference on Large Power Grids defines the functions and control methods and objectives of wide-area protection. The wide-area protection system includes two aspects: relay protection and safety automatic control. Among them, wide-area relay protection is an important part of wide-area protection, and it can adapt to traditional main protection, improve protection value, and simplify protection coordination. It plays a key role in shortening the protection action time, etc., and helps to fundamentally solve the problems of poor adaptability, complexity and coordination of existing relay protection, and improve the adaptive ability of protection. In 1998, Japanese scholar Yoshizumi Serizawa combined wide-area ideas with relay protection and proposed the idea of ​​transmitting multi-point current information via Fibre Channel over GPS to form wide-area differential protection. The range of current differential protection is not limited to an electrical component, but extends to the adjacent area of ​​the component, which not only provides fast differential main protection for the component, but also provides small delay and good selectivity for adjacent regions. Differential backup protection to improve the performance of the protection system. Some scholars have proposed a wide-area current differential protection system based on multi-agent. The expert system is used to realize the dynamic online division of current differential and backup protection zones, and then the coordination of the protection agents is realized. Backup current differential protection. Wide-area backup protection can be realized by the expert system method. Under the premise of the topology of the given network, the action of the relay in the adjacent substations and the opening and closing state of the circuit breaker, the defined action factor AF (acTIon factor) is utilized. The size of the ) to determine the location of the fault. AF describes the possibility of determining the failure of a component based on all active protection devices. This method is designed to ensure that the fault is properly isolated in the event of a primary protection fault. An important functional feature of the smart grid is self-healing. “Self-healing†refers to the isolation of faulty components in the grid from the system and the ability to quickly return to normal operation with little or no human intervention, while virtually uninterrupted power to the user. service. Communication between local and remote devices helps analyze system operating conditions such as faults, voltage drops, and overloads, and takes appropriate control actions based on these analyses. The smart grid will safely and seamlessly allow a variety of different types of power generation and energy storage systems to be connected to the system, simplifying the networking process. In the future smart grid, the self-healing characteristics of the grid will put forward higher requirements on the selectivity, reliability, quickness and sensitivity of relay protection, and put forward new requirements for the conventional relay protection configuration method. In these aspects, depending on the actual situation, there will be some emphasis. The construction of UHV power grid and the expansion of power grid scale will lead to a large increase in short-circuit current. Therefore, the problems such as the reduction of the fixed value reliability factor and the operation of the short-circuit current suppression equipment caused by the increase of short-circuit current are analyzed, and corresponding countermeasures are proposed. The flexible access of the distributed power supply, the backup protection coordination brought by the operation mode of the multi-transformer, the bidirectional power flow, the change of the system impedance, etc. all bring difficulties to the setting of the relay protection setting, and the adaptability of the protection setting will also be A severe test. At the same time, the smart grid will bring new opportunities for the development of relay protection. The new sensor technology used in the smart grid, such as electronic or photoelectric transformers, is not affected by the saturation of traditional electromagnetic transformers. The acquisition of the quantity is more precise, which simplifies the protected data algorithm and shortens the data processing time. Smart grid data synchronization technology, clock synchronization technology, communication technology, computer technology and IEC 61850 standard application can provide high-precision synchronization of data collection in a regional scope, meet the real-time nature of data acquisition and transmission, and ensure redundancy of data transmission process. And reliability; can also provide technical support for the realization of new principles, industrial control technology in the application of power systems, providing a basic support for the new principles, new algorithms and practical applications of wide-area protection. When wide-area relay protection is applied in practice, if centralized protection is implemented in the whole system, a large number of data collection points, massive data, transmission distance and speed will increase the implementation of wide-area relay protection due to the increase in system scale. Difficulty will also increase the difficulty of protection configuration, operation and maintenance, and it is difficult to guarantee the reliability of protection. Therefore, it is also necessary to combine the actual system to establish the regional structure of wide-area relay protection, comprehensively consider and rationally utilize the new smart grid technology, so that wide-area relay protection is more conducive to practical applications. Accusure Pulse Oximeter,Blood Oxygen Meter,Spo2 Monitor,Spo2 Sensor GANSU PINGLINAG ABAY SCIENCE&TECHNOLOGY CO.,LTD , https://www.yzwtech.com
The development of wide-area protection and the impact of smart grid on it and the measures and technical considerations
1 Overview