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Discussion on the technical basis and characteristics of digital substation at present
Discussion on the technical basis and characteristics of digital substation at present

? Paper Keywords: basic characteristics of digital substation technology

? The continuous development of contemporary science and technology promotes the application and development of microelectronics and information technology in power system. At the same time, the introduction of digital technology has also changed the operation mode of substation. With the introduction of digital technology in substation, the secondary equipment of substation gradually extends to the primary equipment. The digitalization process of traditional substation makes the operation of substation more automatic and management more scientific, so it is of great significance to study the technical basis and characteristics of digital substation.

With the development and application of digital technology, digital substation has technical support. At present, China's digital substation technology mainly includes digital electricity measurement system. The technical basis of substation automation mainly includes: intelligent switch, photoelectric current-voltage transformer, primary operation equipment, online state detection system, operation training and simulation technology. The characteristics of digital substation and the influence of technology will inevitably make digital substation a development trend. This paper discusses the main technical basis and characteristics of digital substation.

1. Technical characteristics of digital substation

At present, digital substation is mainly composed of digital primary equipment and networked secondary equipment, such as electronic transformers and intelligent switches. On the basis of IEC6 1850 communication standard, the requirements of continuous informationization, automation and intelligence of substation system are gradually realized.

First of all, the information of electrical equipment in the substation can be shared and utilized with each other through digital technology, which makes the operation more convenient, reduces the times and time for relevant equipment in the substation to quit, reduces the loss, improves the service time of the equipment, simplifies the number of automation equipment, greatly simplifies the secondary wiring of the substation, improves the reliability of the substation equipment use system, and timely maintains and updates the equipment functions in the extended substation.

Secondly, gradually realize the information sharing between substation information and other supporting systems, reduce the repeated construction of resources, which is conducive to the recovery of investment costs and prolong the service life of substations. Reduce the maintenance cost and construction cost in the cycle. The main symbol of digital substation is the digitization of data acquisition. Using digital electrical measurement tools such as photoelectric transformer and electronic transformer, the current and voltage are collected and measured, and the effective isolation of primary and secondary systems in substation is realized. Thereby expanding the range of dynamic measurement of substation electricity. At the same time, due to the digitalization of collection, the measurement accuracy of electric quantity is improved. While preparing to realize substation information sharing, it provides an information foundation for the redundancy of substation equipment to information redundancy in the past, and makes the collection and measurement of substation electricity gradually move towards informationization and integration.

Thirdly, the distribution of substation information system is hierarchical. In the past, the substation automation system was mainly centralized, and the digital substation changed from centralized to distributed. By adopting the second generation hierarchical distributed automation system, the digital substation can record the information of each equipment in the substation more completely and display it in time, which greatly improves the speed and openness of network communication.

Based on IEC6 1850 communication standard, a three-layer structure model of digital substation is proposed, including process layer, interval layer and station control layer. High-tech technologies such as object-oriented modeling, software reuse and embedded real-time operation control system can be adopted to continuously meet the real-time and reliability requirements of power systems such as digital substations. It can not only effectively solve the problem of information exchange between heterogeneous systems in substations and the system operation problems caused by different equipment, but also provide strong technical support for the layered and distributed mode of digital substations.

2. Technical basis of digital substation

At present, the technical foundation support needed by digital substation mainly includes unconventional sensors; Reliable and stable communication network; Stability of components in digital substation.

At present, the construction of digital substation in China is an inevitable trend of applying modern science and technology. With the research and solution of many technical problems in substations, the technical foundation of digital substations is becoming more and more stable. First of all, the technical foundation of digital substation can be seen through the equipment composition of digital substation. The technical equipment of digital substation is mainly composed of electronic voltage and current transformer, intelligent primary equipment and networked secondary equipment.

Electronic voltage-current transformer mainly uses Rogowski coil to divide the resistance, resistance and capacitance, thus replacing the traditional electromagnetic current-voltage transformer. In this way, the electronic current-voltage transformer of digital substation adopts advanced electronic components and electromagnetic compatibility design, which can directly control current and voltage information. Through intelligent comprehensive measuring devices such as digital instruments, information such as current and voltage is measured by computer technology, and digital processing is carried out to realize online monitoring and protection of electrical equipment in the national power grid. However, the conventional transformer in the traditional substation is very different from the electronic transformer, which is not only more complicated in insulation than the electronic transformer, but also larger in volume and smaller in dynamic measurement range of weight. It is not as good as electronic transformer to eradicate the hidden danger of major power outage in the operation of power system and ensure the safety and personal safety of electrical equipment in national substations.

Intelligent primary equipment is mainly based on the standards of substation related equipment, which not only has the basic functions of ordinary traditional substation switchgear, but also is more intelligent on this basis. In addition, the intelligent primary equipment of digital substation can also be monitored online, and a series of advanced intelligent equipment in substation can be operated through digital interface and intelligent electronic switch. Therefore, the intelligent primary equipment in digital substation is an important basic equipment of digital substation, which can provide detection signal loop and control operation drive loop. The design of microprocessor and photoelectric technology by computer simplifies the structure of traditional electromechanical relay and control loop. At the same time, intelligent primary equipment provides a technical basis for digital substation, and it is beneficial to the secondary circuit of substation by connecting with digital public signal network through digital program controller. At the same time, photoelectric digital and optical fiber have also replaced the traditional high-voltage analog signals and control cables. It also saves the cable consumption of the substation, reduces the floor space, shortens the debugging period of the digital substation and the electrical distance of the electronic voltage transformer. More importantly, through intelligent primary equipment, digital substation provides online detection, reducing human error and optimizing control loop.

Finally, the networked secondary equipment of the substation. The conventional secondary equipment in traditional substation is mainly composed of relay protection device, anti-misoperation locking device, measurement and control device and so on. These networked secondary devices can be standardized and modularized for computer microprocessors. Through the connection of network communication channels between networked auxiliary devices, data resources can be enjoyed and information transmission can be accelerated.

3. Technical Status of Digital Substation in China

At present, China's digital substation technology mainly includes digital electricity measurement system. It can be said that it is very important to build a digital substation and have a stable electricity measurement system. At present, voltage transformer system is called unconventional transformer in the world, which is very different from the traditional transformer used in substation in the past.

Among the new voltage transformers, the ones based on electro-optical effect are called optical current-voltage transformers or passive transformers, and others are called electronic current-voltage transformers or active transformers. As we all know, due to linear birefringence and the decrease of luminous intensity of light source devices, the polarization angle change caused by light in the transmission process and the intermediate Wilder constant in different materials are also affected by external temperature, which leads to unstable measurement accuracy of passive transformers. On the other hand, optical transformer has the advantages of good linearity, measurement accuracy, passivity and immunity to electromagnetic interference. At present, the advantages of this new transformer need to be adopted in the digital substation in China, and the stability of substation work can be improved through its working principle.