With the further improvement of the automation level of power plants, dcs systems play an increasingly important role in the entire production process system, so the requirements for stability and reliability are getting higher and higher. Now the reliability of the entire DCS system has been required to reach 99. More than .9%, and the communication system as a key subsystem of the DCS system, its reliability and real-time directly affect the entire DCS system. Therefore, in order to effectively improve the reliability of the DCS communication system, DCS manufacturers often adopt the following measures: 10 Mm Nano Tip,Smart Board Touch Screen Pen,Electronic White Board Pen,Infrared Touch Screen Pen Shenzhen Ruidian Technology CO., Ltd , https://www.wisonen.com
1) Redundant configuration. Now all power plant DCS system backbone communication networks are generally redundant, and some also achieve multiple redundancy, so that the communication network can maintain high availability.
2) Use optical fiber as the transmission medium. As we all know, optical fiber not only has the advantages of long transmission distance, large communication bandwidth and corrosion resistance, but also has outstanding advantages such as strong anti-electromagnetic interference capability and low transmission error rate. These are conventional transmission media such as copper cables and twisted pairs. Unmatched, it has been widely used in the backbone communication networks of communication systems and automation systems in recent years. It can be predicted that with the further decline in the price of optical fiber products and the need for the physical dispersion of DCS systems, the use of optical fibers will continue to expand.
3) Network configuration. This measure not only effectively isolates the data traffic of each layer, improves the real-time communication, but also isolates the communication faults and limits the impact of the faults to the minimum extent as much as possible, thereby improving the reliability of the entire communication system.
4) Automatic bumpless switching under network failure. All DCS communication systems have online monitoring functions. Once the working communication network fails, the system will automatically switch to the redundant network in the hot standby state to ensure continuous and uninterrupted operation of the entire system. In some systems, redundant networks Switching periodically to prevent the hot standby network from being misdetected when an error occurs, thus losing the hot standby function.
5) Data integrity check and automatic retransmission function. In most systems, data integrity (such as CRC mode) is performed before and after all data messages are sent. Once an error occurs, the data retransmission function is automatically triggered.
6) Automatic disconnection and bypass of the faulty station. The failure of any one node will not affect the communication of the entire network, and the faulty node should be automatically disconnected and bypassed. Once the fault is removed, the node can automatically recover data traffic for the entire network.
7) The communication processor and the control processor are separated. In some systems, the control processor and the communication processor are two completely independent processors, each of which performs its own functions and does not interact with each other, thus ensuring the response speed of the control algorithm of the control unit, and at the same time Ensure the real-time and security of network communication, avoiding the slow response of the network communication fault to the control response or the effective transmission of the network due to the complexity of the control algorithm.
In addition, the use of open network topology and communication protocols is also an important measure to improve the reliability of the entire system. In the early DCS system, because common network systems and communication protocols were difficult to meet the requirements, many vendors developed proprietary communication systems and proprietary communication protocols, but their biggest drawback was their specificity, and the manufacturers were closed to each other. The need for manufacturers to continuously improve and develop, resulting in high development costs. With the rapid development of computer network technology, IEC8802.x, (corresponding to the familiar IEEE802.x standard) series of standards have been introduced one after another, the performance and reliability of general-purpose computer networks continue to increase, and the price drops rapidly. Under the trend, major DCS vendors have abandoned the practice of developing their own unique network products, and switched to a general computer network structure and related hardware and software products. The most typical example in this regard is the use of FDDI networks in control networks, due to FDDI. Designed for high-speed backbone networks, the inherent dual-ring topology makes it not only redundant, but also fault-tolerant. It maintains the normal communication of the entire system even when the dual rings are disconnected at the same time. These FDDI standard features make Vendors do not need to design their own seamless switching system between redundant control networks. At the same time, because the FDDI network is designed for the backbone network, it has a large number of standard hardware interconnected with conventional Ethernet and Token Ring. Therefore, it has good openness and high reliability.
The biggest benefit of open network to DCS vendors is that the openness and reliability of the system are significantly enhanced. This is because the professional leaders of the communication field have strong technical strength, and the reliability and openness of their communication system hardware and software products are long-term. It has been fully verified in use. By adopting an open communication system, the DCS system provides the possibility of interoperability between hardware and software products of different manufacturers, which is beneficial for users to freely select related products in a wider range to achieve a better performance-price ratio. The most successful examples are the emergence of fieldbus technology and the application of Ethernet technology in industrial control. It can be said that the openness of the DCS system has gradually become an increasingly important indicator. An additional benefit of using an open system is that it effectively reduces the developer's R&D costs and speeds up product updates.