In mechanical and electrical products in the application of railway electric power monitoring and control system

In mechanical and electrical products in railway power monitoring system, the application of newmaker welcome to e hall exhibition hall 3 PLC PLC programmable controller, PLC programming cable. 。 。 Abstract: this article mainly discusses in PLC controller and HMI and various extension module applied in the electric power monitoring and control system in a railway projects, including power signal acquisition, data processing, data communications, logical switch quantity control, etc. Key words: data collection, float, ASCII, alarm, RS and communication. In a large one, the introduction industrial control products always pay attention to the application of automatic control system is powerful, stable performance, low failure rate. As a main control device and the upper machine PLC and HMI plays an important role in it, share with the whole control system in most of the execution and monitoring tasks. In the electric power monitoring and control system, main control device must be based on the system of signal such as voltage, current, frequency value of the whole power system for accurate control of the actuator, and by the upper machine data real-time monitoring of these signals. System architecture: 1, the whole monitoring system is divided into two monitoring ark: A and B cabinet, specific electronic configuration in the following table 2, the working principle of the monitoring system diagram control system shows that: 1. As shown in figure 1, on A screen and B screen, PLC module by DI and AI read numerous fault alarm signal, Switch quantity) And the rail system in the current, voltage or frequency signal ( Analog A/D conversion) 。 Such as the table below the alarm signal: electric parameter signals: 2. HMI through COM1 or COM2 two RS232 port monitor A and B respectively on PLC, the system of the electrical signals in real-time monitoring, at the same time, according to the switch signal input, using macro instruction on the system running status of all kinds of warning, alarm information and record history. The following figure: 3. On-site power system monitoring and operation is done by HMI, but at the same time, this a series of parameters in the system must be transmitted to the PC, data acquisition, classification, statistics and display function. To the PC data acquisition software has good development, by the user cannot change, the following figure. 4. The software of data acquisition principle for 'accept not hair', and receive only accord with certain agreement of data ( Parameter format must be a floating point number, transmission in ASCII format) And other format data are unable to collect and display. For example: 5. In this way, the PLC must satisfy the end points: floating point Numbers, ASCII data conversion, data only don't accept. At the same time, according to the data acquisition software data format definition, the parameters of A and B cabinet must be A certain rules of combination classification; After restructuring of data sent to the PC, in order to be effective. Otherwise or PC software acquisition is less than the correct data, unable to display properly; Or PLC application to communication mistakes. 6. According to the characteristics of the above, decided to take the following approach to data collection, as shown in figure 1, A cabinet PLC through the RS485 ports in the MODBUS protocol communication way first reads related parameters in tank B PLC controller. In A cabinet, PLC, related electric parameters of A and B cabinet and reassembled into A floating point number. Floating-point conversion: high and low byte exchange: convert the combination after finishing city ASCII format, and according to the acquisition software support agreement format and 'code', 'command', 'the checksum', 'stern code', etc. , as shown in figure 1, A cabinet PLC through the RS485 ports, using RS command sends the data to PC, at the same time will receive the data length is set to 0, implement the data 'only hair don't accept'; As the data length is very long, while the RS at best, can only send 255 bytes instruction at a time; Several times to RS instructions sent. , finally, as shown in figure 2, as long as the PC receives the data in accordance with its agreement format, data acquisition software will automatically in the blank area shows that receives data, and in such as 'system input analog data', 'the alarm status' data block shows the corresponding electric parameters such as values. 7. PLC is repeated in the data acquisition, can in the current PC real-time display system of power parameters. Achieve the result of power system parameter monitoring and timely collection. Four, summary after weeks of the system debugging and improve customer satisfaction after acceptance. In general, the system of large amount of data, the monitoring on the HMI pages to 80 pages; In order to guarantee the HMI in PLC communication speed, general shoulds not be too much monitoring device is placed on a single page. The biggest difficulty lies in the electric power parameter will be sent to PC by PLC acquisition software; Because of the large amount of data, and the complex protocol format, so in the PLC program must write protocol data carefully and strictly arrange every communication data timing relationships, prevent data dislocation or confusion.
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