Application of Fiber Optic Communication in Power System Relay Protection Equipment
In China, transmission lines of 220kV and above are still the main power transmission channels. The main characteristics of these channels are large transmission capacity and high voltage level. However, once an accident occurs during the transmission process, it will cause serious damage to the entire power system, ultimately affecting the safety and stable operation of the entire power system, endangering people’s lives and property safety. Therefore, the usual practice is to use relay protection devices to quickly cut off various faults that occur in high-voltage power lines. Due to the significant role played by relay protection in the entire power system, fiber optic communication is generally used as the physical transmission channel for the protection signals of relay protection devices. This is mainly because the application of fiber optic communication technology in relay protection has the main advantages of large information transmission capacity, strong anti-interference ability, and high transmission quality, as follows:
1. Large amount of information transmission
For long-distance communication transmission, the main technology used is fiber optic communication technology, which benefits from the main advantages of fiber optic communication technology in terms of transmission frequency bandwidth and large information transmission volume. In the power system, the commonly used carrier frequency is generally low and far from meeting the growing demand for electricity, while the carrier frequency used by optical fibers is at least one hundred times that of the commonly used carrier frequency. Therefore, the widespread use of fiber optic communication technology in relay protection can not only meet the higher requirements of the growing power demand for relay protection, but also greatly improve the reliability and accuracy of relay protection.
2. Strong anti-interference performance
In order to ensure that high-voltage equipment or transportation lines do not generate induced magnetic field interference in optical fiber lines, quartz with good insulation performance is mainly used as the basic material for optical fibers. The application of optical fibers in relay protection can effectively avoid unnecessary interference, which is a major advantage of optical communication technology. The good operation of the power grid has little impact on the fiber optic longitudinal protection channel. With the increasing demand for stability in the power system and the continuous improvement of system voltage levels by power users, fiber optic communication technology has been widely applied due to its many advantages, and has achieved a series of good results after use.
3. High transmission quality
In fiber optic communication technology, its undeniable advantages are good confidentiality, low signal interference, and high fiber optic transmission quality. The basic requirements for relay protection speed in high-voltage transmission systems happen to require these characteristics of optical communication technology. Optical communication transmission technology can ensure the consistency of information between the issuing port and the receiving port, thus ensuring the normal, stable, and accurate transmission of the line.
There are two main communication methods between fiber optic channels and relay protection: dedicated fiber optic communication and multiplexed fiber optic communication. Each communication method has its own characteristics and applicable situations, and the choice of method should be based on the actual situation during use.
The first method is dedicated fiber optic communication. The dedicated communication method only transmits relay protection information and does not transmit other information, mainly because the dedicated communication method is a dedicated fiber optic channel established specifically for relay protection. The communication distance of dedicated communication methods is generally within 100km, which can meet the basic requirements of power enterprises. This type of method has the characteristics of high transmission efficiency, simple approach, and no intermediate links or equipment, and can be effectively applied to the transmission of information in short distance relay protection.
The second method of multiplexed fiber optic communication. The multiplexing communication method is mainly composed of the coordination of various optical fibers in the longitudinal protection. The relay protection device will emit permission signals and direct jump signals under the allowed mode, and then the audio interface signal will be transmitted to the relevant multiplexing equipment, and then transmitted to the fiber optic channel. The simple wiring is a major advantage of this transmission method, which plays an important role in promoting the maintenance and operation of the circuit system. The reuse of fiber optic communication is widely used in long-distance line protection.
Due to its many advantages, fiber optic channels are widely used in relay protection equipment. With the development of the times and the advancement of technology, China’s relay protection will face the development of informatization, networking, and intelligence in the future, which puts higher requirements on the work of relay protection and the core component of optical fiber communication, the optical module. On the one hand, there is enormous market potential, with nearly 300000 shipments of relay equipment related optical modules in the segmented market in 2021. It is expected that the market demand will increase by 15% annually. On the other hand, thermal control and design of optical modules pose more severe challenges. The requirements for stability and reliability of relay protection equipment limit some commonly used heat dissipation designs, such as prohibiting the use of fans inside the equipment; The higher protection level requirements limit the opening of the chassis for heat dissipation. Normally, only natural convection and conduction can be used to control the internal environmental temperature of the equipment to meet operational requirements. Therefore, with the continuous increase in board level heat consumption and the limitations of some traditional heat dissipation methods due to standards, it is difficult to effectively design heat dissipation for modules. Effective product thermal design methods are needed, and the introduction of new materials and processes is explored.
The reasonable application of fiber optic communication technology can smoothly improve the functionality and safety of relay protection, thereby meeting the basic needs of power enterprises, completing the protection of related lines, and promoting the safety and stability of the power system.
