A brief discussion on the technical foundation and characteristics of the current digital substation
Keywords of the paper: Technical basic characteristics of digital substation
Abstract of the paper: The continuous development of contemporary science and technology has promoted the The application and development of microelectronics technology and information technology in power systems. At the same time, the introduction of digital technology has also changed the operation of substations. The introduction of digital technology in substations has gradually extended the secondary equipment of the substation to primary equipment. The digitalization process of traditional substations has made the operation of the substation more automated and the management more scientific. Therefore, it is of great significance to study the technical foundation and characteristics of digital substations.
The development and application of digital technology has provided technical support for digital substations. At present, my country's digital substation technology mainly includes digital electrical quantity measurement systems. The automation technology foundation of the substation mainly includes: intelligent switches, photoelectric current and voltage transformers, primary operation equipment, online status detection systems, operation training simulation technology, etc. The characteristics of digital substations and the impact of technology will inevitably make digital substations a development trend. This article discusses the main technical basis and characteristics of digital substations.
1. Technical characteristics of digital substations
The current digital substation is mainly composed of digital primary equipment such as electronic transformers and intelligent switches, and networked secondary equipment. It is based on the IEC61850 communication specification. Gradually realize the requirements of continuous informatization, automation and intelligence of the substation system.
First of all, the electrical equipment information in the substation can realize mutual resource sharing and utilization through digital technology, making the operation more convenient, while reducing the number and time of withdrawal of relevant equipment in the substation, and reducing losses. , improve the service life of the equipment, streamline the number of automation equipment, greatly simplify the secondary wiring of the substation, improve the reliability of the substation equipment usage system, maintain and timely update and expand the equipment functions in the substation.
Secondly, it gradually realizes the sharing of substation information between its system operation and other supported systems, reducing duplication of resource construction, conducive to the recovery of investment costs and extending the life of the substation. Years of use. Reduce maintenance costs and construction expenses during the cycle. The main sign of a digital substation is the realization of digitization of data collection. By using digital electrical measurement tools, such as photoelectric transformers, electronic transformers, etc., to collect current, voltage, etc., the collection and measurement of these electrical quantities, Effective isolation of the primary and secondary systems of the substation is achieved. Therefore, the range of dynamic measurement of electrical quantities in the substation is increased. At the same time, the digitization of collection also improves the measurement accuracy of electrical quantities. While preparing to realize the ultimate sharing of substation information, it provides an information basis for the past redundancy of substation equipment to move towards information redundancy, and gradually makes the collection and measurement of electrical quantities in the substation move toward informatization and integration.
Third, the distribution of substation information systems has become hierarchical. In the past, the automation system of substations was mainly centralized, but the digital substation has changed the previous centralized system and adopted distributed system. By adopting the second generation hierarchical distributed automation system, the digital substation can more completely record the information of each device in the substation and display it in a timely manner, which greatly improves the speed and openness of network communication.
Based on the IEC61850 communication specification, the three-layer structural model of the digital substation is proposed, including the process layer, bay layer and station control layer. Object-oriented modeling can be used, and high-tech technologies such as software reuse and embedded real-time operation control systems can be used to continuously meet the real-time and reliability needs of power systems such as digital substations. Not only can it effectively solve the problem of information interoperability between heterogeneous systems in the substation and the system operation problems caused by different devices, but it also provides strong technical support for the hierarchical distributed model of the current digital substation.
2. Technical foundation of digital substation
The technical foundation support required by the current digital substation mainly includes unconventional sensors; reliable and stable communication network; and the stability of the components of the digital substation.
my country's current digital substation construction is an inevitable trend in the application of modern science and technology. With the research and solution of many substation technical problems, the technical foundation of digital substations has become increasingly stable. First of all, the technical foundation of the digital substation can be seen through the equipment composition of the digital substation. The technical equipment of digital substations mainly consists of electronic voltage and current transformers, intelligent primary equipment, and networked secondary equipment.
Electronic voltage and current transformers mainly use Rogowski coils to perform resistive voltage division, resistance-capacitance voltage division and capacitive voltage division, thereby replacing the traditional electromagnetic current and voltage transformers. In this way, the electronic current and voltage transformer of the digital substation adopts advanced electronic components and electromagnetic compatibility designs, which can more directly control current and voltage information. And through intelligent comprehensive measurement devices such as digital instruments, computer technology is used to measure information such as current and voltage, and digital processing is performed so that electrical equipment in the national grid can be monitored and protected online. The conventional transformers in traditional substations are very different from electronic transformers. Not only are the insulation complex than electronic transformers, but they are also larger in size, heavier and have a smaller dynamic measurement range; they are not as good as electronic transformers. Transformers can eradicate major power failure hazards during the operation of the power system and ensure the safety of electrical equipment and personal safety in national substations.
Intelligent primary equipment is mainly based on the specifications and standards of substation-related equipment. It not only has the basic functions of ordinary traditional substation switching equipment, but also is more intelligent on this basis. In addition, the intelligent primary equipment of the digital substation can also perform online monitoring and use digital interfaces and intelligent electronic switches to operate a series of advanced intelligent equipment in the substation. Therefore, the intelligent primary equipment in digital substation is an important basic equipment of digital substation, which can provide detected signal loops and controlled operation drive loops. The design of microprocessing and photoelectric technology through computers simplifies the structure of traditional conventional electromechanical relays and control loops. At the same time, intelligent primary equipment provides the technical foundation for digital substations, and is connected to the digital public signal network through digital programmable controllers, which is beneficial to the secondary circuit of the substation. At the same time, optoelectronic digital and optical fibers have also replaced traditional high-power analog signal and control cables. It further saves the amount of cables used in the substation, reduces the floor space, and shortens the operation cycle of the digital substation and the electrical distance of the electronic voltage transformer. More importantly, through intelligent primary equipment and digital substations, while providing online detection, human errors are reduced and the control loop is optimized.
Finally, networked secondary equipment in the substation. Conventional secondary equipment in traditional substations mainly consists of relay protection devices, anti-accidental locking devices, measurement and control devices, etc. These networked secondary equipment can be standardized and modularized with computer microprocessors. Through the connection of high-speed network communication channels between networked secondary devices, maximum sharing of data resources and high-speed information transmission can truly be achieved.
3. The current technology of digital substations in my country
At present, the technology of digital substations in my country mainly includes digital electrical quantity measurement systems. Having a highly stable electrical quantity measurement system is crucial to building a digital substation. Currently, the voltage transformer system is called unconventional transformer in the world. This kind of voltage transformer is very different from the traditional transformer used in previous substations.
Among the new voltage transformers, the voltage transformers based on the electro-optical effect are called optical current-voltage transformers or passive transformers, while the rest are electronic current transformers. Pressure transformer is also called active transformer. As we all know, due to the linear birefringence phenomenon and the luminous intensity of the light source device will decrease, the polarization angle change caused by the light transmission process and the Verde constant of different materials will also be affected by the external temperature, resulting in passive mutual inductance The measurement accuracy of the instrument is unstable and other problems. Optical transformers have the advantages of relatively good linearity, measurement accuracy, passiveness, and not easily affected by electromagnetic interference. my country's current digital substation needs to adopt the advantages of this new type of transformer to improve the stability of the substation through its working principle.