The development trend of relay protection technology is towards computerization, networking, intelligence, and the integration of protection, control, measurement, and data communication. With the rapid development of computer technology and its widespread application in the field of power system relay protection, new control principles and methods are continuously being applied to computer-based relay protection to achieve better results, thereby advancing the research of microcomputer-based relay protection to a higher level and giving rise to some notable new trends.
1 Application of Adaptive Control Technology in Relay Protection
The concept of adaptive relay protection originated in the 1980s. It can be defined as a new type of relay protection that can change protection performance, characteristics, or settings in real time according to changes in the power system's operation mode and fault state. The basic idea of adaptive relay protection is to make the protection adapt to various changes in the power system as much as possible, further improving protection performance. The emergence of this new protection principle has attracted great attention and interest. Adaptive relay protection has advantages such as improving system response, enhancing reliability, and increasing economic benefits. It has broad application prospects in fields such as distance protection of transmission lines, transformer protection, generator protection, and automatic reclosing. In response to the impact of power system frequency changes, the influence of transition resistance during single-phase-to-ground short circuits, the impact of power system oscillations, and fault development issues, adaptive strategies have been proposed, and the feasibility of implementing adaptive microcomputer-based distance protection has been explored from both theoretical and practical perspectives.
2 Application of Artificial Neural Networks in Relay Protection
Since the 1990s, artificial intelligence technologies such as neural networks, genetic algorithms,cable fault tester is divided into three parts, used for testing various faults of power cables, locating cable paths and burial depths, and daily maintenance management of cable archives. Evolutionary planning, fuzzy logic, etc., have been applied in various fields of the power system, and some research work in the field of power system protection has also shifted towards artificial intelligence research. Expert systems, artificial neural networks (ANN), and fuzzy control theory are gradually being applied in power system relay protection, injecting vitality into the development of relay protection.
Artificial neural networks based on biological nervous systems have characteristics such as distributed information storage, parallel processing, self-organization, and self-learning. Their application research is developing very rapidly, currently focusing mainly on artificial intelligence, information processing, automatic control, and nonlinear optimization. In recent years, in the field of power system relay protection, artificial neural networks have been used to implement fault type identification, fault distance measurement, directional protection, and main equipment protection. A method for implementing adaptive current protection using artificial neural networks is proposed. This method fully utilizes the powerful adaptive ability, learning ability, and pattern recognition ability of artificial neural networks to identify various fault conditions in the power system, solve the problems of sensitivity compensation and fault direction identification in current protection, ensure that current protection has sufficient protection range for all faults in the forward direction, and block all faults in the reverse direction, thereby achieving adaptive current protection.
3 Substation Integrated Automation Technology
Modern computer technology, communication technology, and network technology provide the technical foundation for optimizing combination and system integration to change the current state of monitoring, control, protection, and metering devices and systems in substations, which are currently separated. High-voltage and extra-high-voltage substations are facing a technological innovation. The close integration of relay protection and integrated automation has become possible, manifested in integration and resource sharing, remote control, and information sharing. With remote terminal units (RTU) and microcomputer-based protection devices as the core, incorporating the control, signal, measurement, and metering circuits of the substation into the computer system, replacing traditional control and protection panels, can reduce the footprint and equipment investment of substations and improve the reliability of the secondary system.
Currently, the monitoring, control, and protection devices used in substations, including fault recorders and emergency control devices, have achieved microcomputer-based digitalization, but they are almost all independent devices with single functions. Each device lacks overall coordination and functional optimization, and functions overlap, input information cannot be shared, wiring is complex, which reduces reliability as a whole. At the same time, it cannot fully utilize the powerful data processing capabilities and speed of microcomputers, and it is also an economic waste. The widely used substation automation system now is a conventional automation system. It applies automatic control technology, computer data acquisition and processing technology, and communication technology to replace manual monitoring, operation, voltage and reactive power control, measurement recording and statistical analysis, fault monitoring, alarm and event sequence recording, and operation for normal operation of substations. Most of them do not involve functions such as relay protection, emergency control, fault recording, RTU, and maintenance status information processing, and their functions are relatively simple.
In summary, microcomputer-based protection will inevitably present newer features with the advancement and development of various technologies, and will also gain broader applications.
