The main technical background of the request.
The development of low-voltage smart appliances has benefited from the development and application of single-chip microcomputers (microprocessors, MCUs), and the development momentum is rapid. However, the introduction of intelligent technology in low-voltage electrical appliances is mainly the tripping device for circuit breakers and some control appliances. The currently widely used design method is to deepen and refine the original functions of the products; it has not yet jumped out of the original frame. . If a typical and more successful representative of an intelligent circuit breaker (the core part is an intelligent trip unit), we can see that although the level of intelligence of this product has reached a certain level, it has a complete set. The fixed protection features, and the introduction of new functions such as ammeters, are ideal compared to traditional products. However, from the point of view of automation control, it is only a simple "point" control component. Other smart appliances often only function to simplify logic circuits, such as smart time relays. On the other hand, intelligent equipment monitoring, protection and information network systems have also been introduced, and its centralized control system makes low-voltage smart appliances must have a data communication interface, otherwise the information exchange of the entire system is quite problematic. At the same time, smart appliances with data communication interfaces in turn promote the further development of the entire low-voltage control network.
At present, the control means of the power system, especially the low-voltage power grid, is mainly relay protection. The "nodes" of the network are basically "point-type" control components; the network uses hierarchical protection to ensure security, relying only on " The point-type "controller's setting value l刖S low-voltage electrical appliances are the basic components of the low-voltage power grid, while the low-voltage smart electrical appliances are the end-executing components of a series of distribution and control intelligent networks such as distribution automation, and the information between them The exchange of data is the basis of the entire distribution network control and management technology. Due to the rapid development of smart appliances and the progress of grid automation control, data communication requirements for low-voltage smart appliances have been proposed. Therefore, the requirements for unifying the data communication protocol of low-voltage intelligent electrical appliances are urgent. Under this circumstance, Shanghai Electric Apparatus Research Institute compiled a data communication protocol for low-voltage electrical appliances according to the characteristics of the industry, and the key technology projects in urban power grids rely mainly on computer communication technology for data communication technology, and the technology is developing very fast. New technologies and new methods emerge in an endless stream; in addition, the data communication of low-voltage electrical appliances has its inherent characteristics and technical foundation; therefore, how to develop a data communication protocol with both technological advancement and low-voltage electrical components is Our current topic.
2Technical background The rapid development of low-voltage intelligent appliances, as well as the progress of power grid automation control, is achieved by the data-level 4 hierarchical setting proposed by low-voltage smart appliances. This is an open-loop control, and it is discrete, that is, there is basically no feedback loop connection between the various "point" control components of the network (sometimes only partially interlocked between the stages), so it is only one Kind of "raw" control. However, from the perspective of the entire industrial system, the control of the low-voltage power grid is more important than one equipment, one pipeline, and the intelligence level is relatively low. Therefore, it is urgent to vigorously develop low-voltage electrical intelligent technology.
At the same time, the development of the "network control" intelligent system for the low-voltage power grid and its rapid development, there have been a number of low-voltage distribution monitoring network systems developed on the basis of intelligent circuit breakers, such as Schneider's products. Various companies have also launched their own monitoring, protection and information network systems for intelligent electrical appliances, but they have not formed a unified pattern, especially in the data communication of low-voltage electrical appliances.
We introduce some domestic situations: the currently available intelligent low-voltage electrical appliances are not enough, but the key smart electrical appliances have been successfully developed in China and have already formed a production scale; such as the intelligent frame circuit breaker developed and produced in the Eighth Five-Year Plan, intelligent Plastic case circuit breakers all have intelligent communication with a communication interface. The "connection" between them and the control network is realized through a computer communication interface. As a smart circuit breaker for power distribution and protection in the power system, it can provide many protection curves (three-stage protection) for user setting during installation, and it is required by the upper computer according to the requirements of distribution automation when the power grid is running. Change these curves in time, so that the intelligent circuit breaker has changed from the original "static" protection to the "dynamic" protection, and the protection level has been greatly improved. Similarly, the data communication protocol of smart electrical appliances in China has not been unified. Therefore, in a control system, only the same type of smart electrical appliances can be used, so that the design and application of the control system has great limitations. The emergence of low-voltage electrical data communication protocols allows the control system to accommodate a wide variety of smart appliances, as long as they have a data communication interface that uses a uniform "protocol", so the design and application of the control system is universal. It is easier to promote and popularize.
In general, smart appliances have a data communication interface, which can enter the control network. The network control makes the control and protection performance of the smart appliances have a "quality" change, and has a data communication interface using a unified "protocol". Make the control network easier to design and apply.
3 characteristics and technical basis of low-voltage electrical data communication For the data communication of low-voltage electrical appliances, it is necessary to determine the three parts. The first thing to consider is the main content of the communication, that is, the information related to the control content of the power network, and how the information is encoded (data code). The second is to consider communication issues; such as data transmission formats, transmission rules. The third is various solutions for the structure of data communication networks.
3.1 Network control content The main content of low-voltage electrical data communication is the object parameters of network control, mainly in the following three categories: low-voltage electrical components themselves working state parameters, such as: working state; on or off, standby state; ready or not prepared Good, alarm, fault; action or no action.
The electrical parameters of the working branch where the low-voltage electrical components are located, such as current (phase separation parameter), fault parameter (fault value, phase) and related parameters.
Control network operating parameters, such as: remote adjustment, remote control 3.2 communication methods need to consider data transmission format, transmission rules, data link symbols, byte format, frame format, function encoding, baud rate, error handling.
3.3 Data communication network structure The hardware structure of the communication interface, such as: 37-core connector (GB9950), 15-core connector (GB9952), 25-pin connector (S/Z9104), network interface R45, etc.
The third layer is connected to the central processing unit (CPU) or microprocessor (MCU) output port of the smart appliance.
The design of the fourth layer processor, there are two programs of single processor and dual processor (one of which is dedicated to data communication).
The physical structure of the communication line, such as: fiber, shielded wire, twisted pair.
Interface hardware and monitoring software and data acquisition software of the upper machine. The corresponding software environment of the communication interface and the modular design of the communication software.
3.4 Characteristics of low-voltage electrical data communication 5 From the perspective of network control, the low-voltage electrical communication content is characterized by strong timeliness. Especially in the case of a failure of the distribution branch, the response time of the system should be on the order of milliseconds. Control systems with zone blocking have higher response time requirements.
4 Low-voltage electrical data read-through specification Low-voltage electrical data communication protocol (VI 0) began to be applied in intelligent low-voltage power distribution and control devices for key technical projects of urban power grids.
The stipulation stipulates the data transmission format, data encoding and transmission rules between low-voltage electrical appliances and low-voltage electrical appliances, between low-voltage electrical appliances and upper-level computer monitoring devices and even with central control systems.
The statute applies to peer-to-peer, point-to-multipoint data communication. 4.1 The main standard specification The main standard is the Ministry of Power Industry Standard Power Load Control System Data Transmission Protocol> (the International Electrotechnical Commission has no relevant publications).
In view of the fact that the standard is mainly used in various point control systems, communication between the control center and the local control unit, the main communication content is power load control, and the real-time control content is relatively small; the load-only trip signal can only reach 1~15 when the load is limited. Minutes (that is, the action time of the planned power cut), mainly based on management information, and the reliability requirements for communication are relatively low, but there is a certain relationship with our communication protocol. For this reason, our statute is as close as possible to the main format. It is common with it.
Another major standard is the mechanical industry standard B/T575591 (ISO 8867-88) industrial asynchronous communication data link layer and physical layer>, since the standard written year is about 87 years, it has been ten years since Therefore, the content is quite old and is used only for general purposes in this Statute.
4.2 Main contents of the statute The specification specifies the parameter type and the corresponding parameter code and communication format. 4.2.1 Low-voltage electrical components working state parameters 4.2.1.1 Working state: On and off 4.2.1.2 Standby state: Ready, not ready 4.2 .1.4 Fault: Actioned, not operating 4.2.1.5 Fault type (four types) 4.2.2 Electrical parameters of low-voltage electrical components and their working branches 4.2.3.1 Remote tuning related parameters 4.2.3.2 Remote control signal 4.3 Communication format specification Data transmission format, transmission rules, data link symbols, byte format, frame format, function coding, baud rate, error handling, etc.
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