Foreword With the rapid development of computer and network communication technology, the era of digitalization and networking of automation systems in various industries has come. This aspect provides a better platform for data exchange, analysis, and application between various control and information systems. On the other hand, it also puts forward higher requirements and accuracy for the accuracy of various real-time and historical data time tags. Not expensive GPS satellite synchronization clocks (NTP time servers) to unify the clocks of various systems have been the standard practice used in current major system designs. For example, the main clocks of large-scale unit distributed control system (SCADA), auxiliary system programmable logic controller (PLC), plant-level monitoring information system (SIS), and plant-station management information system (MIS) synchronize clocks through appropriate GPS satellites. The (NTP time server) signal interface obtains the standard TOD (year, day, minute, second) time, and then according to the respective clock synchronization mechanism, the slave clock deviation in the system is limited within a sufficiently small range, thereby achieving the clock of the entire system. Synchronize.
1. Overview The SCADA function of the water conservancy automation pumping station information collection system provides the dispatcher and central controller with real-time data and information of each pump station, and they can conveniently perform accident replay or historical data and information query. When designing the system, more considerations must be given to the network architecture, the communication protocol conversion, the data storage medium, and several performance index requirements that satisfy the SCADA function, without considering the impact of the system-wide network clock being out of synchronization. Because the system-wide clock is not synchronized, it will cause some special faults, such as data and information loss, SOE event information logic confusion, certain workstations crashes, and even system defects. Therefore, in order to eliminate clock synchronization effects, we need to analyze clock synchronization. The important role and various implementations in the SCADA system.
The pumping station SCADA acquisition system is a real-time system. It collects real-time data and information from each pumping station. After processing by software and hardware, data and information are displayed at the pump station workstations or stored in the historical database. The SCADA acquisition system is divided into a master control system and sub-pump station systems, so the whole network clock synchronization is performed in two parts:
1 The master console system synchronizes with the server clock in each operation;
2 Clock synchronization between the master control unit and the smart unit of each sub-pump station system;
2, the total control system clock synchronization
The purpose of synchronizing the clocks of the workstations of the master control system with the master server is to ensure the consistency and integrity of the entire network when data is added, changed, or deleted. The inconsistency and incompleteness of data can cause the master/slave system to switch or historical data to be stored. The consistency and completeness of the data cannot be correctly identified, resulting in the loss of information and data, and even lead to system failure. Since the crystal oscillator chips of each workstation and server are operated for a long time, the problem of clock inaccuracy due to leakage or other reasons may occur. Therefore, a corresponding method must be adopted to realize the synchronization of the network clock of the master-control end system, as shown in the figure. Method: The clock synchronization mode of the master console system is generally based on the figure, because the K806 model GPS satellite synchronization clock (NTP time server) device can not only provide a network interface but also provide multiple NTP network interfaces, and in addition to achieve the GPS clock Synchronization, servers, workstations and front-end machines do not need to run other processes, just to start the system NTP service, which greatly saves system resources.
3, the pump system clock synchronization
The purpose of clock synchronization between each sub-pump station system and master control system clock and each smart device of the pump station is to ensure real-time acquisition of the data information of each interval smart unit. After the master control system is processed, it can correctly repeat the data or The time, sequence and logical relationship of the information. Based on the displayed data and information, the dispatcher and controller can master the running status of each pump station in real time, thereby ensuring economic dispatch and safe dispatch.
The clock synchronization mode of each substation pump station system workstation uses a special network clock synchronization, which can improve the accuracy of clock synchronization, and it is convenient and quick, and at the same time reduces the resource burden of the smart unit. The smart unit in each subpump system adopts the clock synchronization method of Figure 2. , Through the serial port or pulse interface of our K806A type GPS satellite synchronous clock (NTP time server) product, the smart unit clock is synchronized.
4. Product Topology Diagram The whole system clock synchronization is divided into two parts. One is the master control terminal and the sub-pump station workstation. We recommend using the K806C model NTP clock server to realize the other, and the other is the smart unit and the acquisition unit (PLC) of the sub-pump station. It is recommended to use the K806A serial serial satellite clock, as shown below:
5. Conclusion As mentioned above, in order to prevent the system network clock from being out of synchronization, such as data and information loss, SOE event information logic confusion, some workstation crashes or even system failures, we must take appropriate measures to achieve system time synchronization.