Design of adaptive line protection under smart grid

Abstract

Smart grid will bring new opportunities to development of relay protection, new sensor technology is used in smart grid. Simplified algorithm to protect data, reducing data processing time. With the State Grid Corporation of China launched the construction of smart grid, smart grid caused by the characteristics of network reconfiguration, distributed power access technologies such as micro-network operation, to put forward new demands on relay protection, based on local measurement information and a small amount of regional information makes conventional protection face greater difficulties to solve these problems; the same time, research and application on new technologies (such as new sensor technology, clock synchronization and data synchronization technology, computer technology, optical fiber communication technology, etc.) provided a broad space for development of relay protection. Adaptive protection means that the protection must adapt to changing system conditions, the computer relay protection must have a hierarchical configuration of communication lines to exchange information with computer network of other devices. For now, fiber optic communication lines are best medium in large amounts of information transmission and conversion in adaptive protection. Adaptive protection is a protection theory, according to this theory, which allows adjustment of the various protection functions, making them more adapted to practical power system operation. The key idea is to make certain changes to the protection system to respond due to load changes, such as power failures caused by switching operations or changes in the power system. Adaptive protection under the relevant literature to a definition: “Adaptive protection is a basic principle of protection, this principle makes the relay can automatically adjust to various protection functions, or changes to more suitable for a given power system conditions.”. In addition to conventional protection, but also must have a clear adaptive function modules, and only in this case can be called adaptive protection. For the general protection adaptive capacity and detect some aspects of complex fault there are some limitations, hardware circuit of microprocessor line protection device is discussed in this thesis, both hardware and algorithm considers the anti-jamming methods. On the software side, the use of a relatively new method of frequency measurement, dynamically tracking changes of frequency, real-time adjustment of sampling frequency for sampling; and using the new algorithm, improving data accuracy and simplifying the hardware circuit. The adaptive principle is applied to microprocessor line protection, adaptive instantaneous overcurrent protection, overcurrent protection principles, etc, to meet the requirements of rapid change operation mode to improve the performance of line protection. Relay protection needs to adapt to frequent changes in the power system operating mode, correctly remove various failure and equipment, and adaptive relay protection maintains a system of standard features in case of parameter changes. The simulation results show that it is an effective adaptive method.