In order to realize maintenance-free and less maintenance step by step, a fully automatic control system combining programmable logic controller (PLC) and ultrasonic level gauge is adopted in tunnel drainage system. Compared with the control system composed of traditional relays, this system has the advantages of safety, reliability, failure rate paper, simple structure, convenient programming, complete functions and high cost performance. Around Dushuhu Tunnel Project, this paper mainly analyses the advantages of programmable logic controller (PLC) and the realization method of programmable logic controller (PLC) in rainwater pump control system, and focuses on the application effect of programmable logic controller in rainwater pump control system, which provides some beneficial basis for future research. Tunnel is a special section, which is easy to cause traffic accidents. Therefore, in order to ensure the normal and safe passage of the tunnel, there are many equipments in the tunnel, such as traffic guidance, environmental detection, traffic detection, ventilation and lighting. Compared with the control system composed of traditional relays, programmable logic controller (PLC) has the advantages of high reliability, versatility, strong anti-interference ability, simple structure, high cost performance, convenient maintenance, and flexible control mode. It has been applied in the drainage system of Dushuhu Tunnel and played a greater role. Modern programmable logic controller, which is called Programmable Logic controller in English, is a new type of industrial device based on microprocessor and highly integrated. It is the product of the combination of computer technology and industrial control technology.
At present, the development of PLC is very fast, and there are many manufacturers. The varieties, specifications and performances of PLC are also different. There is no unified standard yet. According to the actual situation and control requirements of the project, and in line with the principle of safety, reliability and economy, we chose Siemens S7-200 small PLC, CPU 224, I/O contacts 14 in/10 out, plus EM231 analog input module (4 input), to receive the analog signal of ultrasonic level meter 4-20mA, and TD200 double-line. Text display, it is very convenient to display the text information and data needed to achieve man-machine dialogue; The Probe integrated ultrasonic level meter produced by Siemens Miaosong Power Company is selected as the ultrasonic level meter. The S7-200-CPU 224 produced by Siemens has a shape size of 120.5 x 80 x 62mm and the size of EM231 analog input module is 191.7 x 80 x 62mm.
It is a compact programmable controller. It is sealed, dustproof, low cost and has a powerful instruction set. With TD200 LCD text display, it can be set up as needed. And the display parameters are displayed on the LCD screen, which is the ideal choice for our rainwater pump control system. Using S7-200 and ultrasonic level gauge to achieve precise and reliable on-site automatic control is incomparable with traditional relays.
Ultrasound level gauge is a high precision sensor which calculates the liquid level height by the time of echo reflected from the liquid surface. It converts different liquid levels into 4-20mA current, connects to the analog input module (EM231) of S7-200, and realizes the automatic control of the pump through PLC programming. It is more accurate than using float switch to control liquid level. It can also modify pump level and stop pump level through TD200 text display, and display liquid level height in real time.
These can not be achieved by using float switch.
Using S7-200 programming, it is convenient to realize automatic control in situ when several rainwater pumps start in turn. Generally speaking, there are several pumps in a pumping house, which are used for several times. Through the traditional relay control, the main pump and the standby pump are relatively fixed, the main pump will start frequently, and the standby pump can start only when several main pumps have faults, and the starting times are very few. In this way, the standby pump is prone to such and such failures due to long-term idleness. Through the S7-200 programming, several pumps can be started in turn, and the frequency of pump use is basically the same, to avoid the above defects, which is powerless for traditional relays. Through the S7-200 communication port, it can communicate with the host computer and realize the monitoring and control function of the monitoring center.
S7-200 (CPU224) has two RS-485 communication ports.
Through RS485 communication port, Modbus communication protocol is used to connect the upper computer in AUC box, and then the optical cable is connected with the server of the monitoring center. It can upload data to the monitoring center (liquid level setting and real-time liquid level, etc.). It can also accept the instructions of the monitoring center and make actions to realize remote monitoring. Control function. Fig. 1 is a fully automatic control schematic diagram of a rainwater pump that can be used by both unattended and unattended persons. Only the control principle of 1 # pump is shown in the diagram. The principle of the other three pumps is the same as that of 1 # pump. As can be seen from the figure, the wiring is simple and intuitive.
If you want to change the control mode, you only need to change the internal program of PLC to meet different control requirements without changing any wiring. Fig. 1 shows that 1KA is a pump start intermediate relay, 2KA is a fault relay, 3KA is a soft start full-voltage start intermediate relay, 4KA is a soft start fault intermediate relay, so many intermediate relays are mainly used as feedback and control; 1HY is a fault indicator lamp, yellow light when thermal relay and pump fail; 1HR is a pump. Running indicator light, bright red when running; 1HG signal stop pump indicator light, bright green when stopping; 7HY high water level alarm, yellow light when water level exceeds the set alarm value; 1KA normal open contact on soft starter triggers soft start; 1KM is by-pass contactor, when soft starter starts under full pressure, this contactor acts through 3KA; 1M-0.0-1 on PLC. M-0.3 is the fault signal input point of four pumps, 2M-1.0 is the switch position signal input point, 2M-1.1 is the fault signal input point of four soft starters. In the automatic state, when the soft starter reports fault, thermostatic element the pump will not start; in the PLC, 1L-0.0?~1L-0.3? In the automatic state, four pump start and stop instructions can be issued, 2L-0.4? High water level alarm. When the switch 1SA reaches the manual state, press 1SB, 1KA action, its usually open contacts trigger the soft starter to start. After several seconds (generally about 8S) start, the soft starter will send a full-voltage start signal, 3KA action, turn on 1KM (self-protection), turn on the soft starter bypass and start the pump completely; when the switch is set to the automatic state, there are two. The control mode is that the PLC itself judges which or which pumps to start through the 4-20mA current conveyed by the ultrasonic level meter to realize the local automatic control. The other is that the central control room sends instructions to the RS-485 communication port of the PLC through the optical cable and ACU to control the operation of the pump remotely, whether it is the local automatic control or the local automatic control. Remote control, feedback signal and liquid level data will be uploaded to the control room for remote monitoring and control of the pump. Rainwater pump control system is an important part of urban tunnel monitoring system. Only by ensuring the orderly operation of the system can the normal and safe operation of the tunnel be ensured. Depending on the length of the tunnel, the same rain pump control system equipment will be installed in different sections. Dushu Lake Tunnel has been opened for ten years. The rainwater pump control system has never had any breakdown, which greatly reduces the amount of maintenance, and can be operated and controlled remotely, so that no one is on duty at all. Tunnel electromechanical monitoring network is mainly composed of remote monitoring center, programmable logic controller (PLC) and related communication lines. Generally, a regional controller will be set as the main control PLC in the tunnel substation, and a regional PLC will be set at intervals. The programmable controller can not only monitor the related mechanical and electrical equipment, but also transmit the monitoring data. It will be applied in the rainwater pump control system.
It can accumulate the running time of each pump and ensure that the running time of each pump is equal. It can automatically control the stop operation of all pumps. The PLC of Dushuhu Tunnel Section composes the optical fiber self-healing loop network. In the tunnel monitoring, there are many mechanical and electrical equipment, and programmable logic controller (PLC) has many optical fiber loop network nodes. Generally, two main control PLCs are set up in the tunnel loop network. Thus, through the communication between the two main control PLCs of the substation and the monitoring center, the regional PLC loop network can realize the connection monitoring. The purpose of the center is to fundamentally increase the communication reliability between the monitoring center and the PLC network, and then to increase the monitoring of the rainwater pump control system. The application of programmable controller in rainwater pump control system is reasonable, which improves the universality of rainwater pump control system. In Dushu Lake Tunnel project, the rainwater pump control system has made some breakthroughs in universality, but there are still some areas that need continuous improvement. For example, the automatic configuration generation of the system needs to be improved, that is, users can realize self-customized monitoring system through simple configuration, considering the flow of rainwater drainage in pumping wells, water level of water gauge and the operation of several pumps at present, on this basis, the number of pumps to be run is determined, and then the operation of pumps to discharge rainwater can be controlled. 。 Programmable Logic Controller (PLC) is the key to the whole tunnel monitoring. Its quality will directly affect the operation and maintenance of the tunnel. In the rainwater pump control system, in order to better enable the programmable controller to transmit and control the amount of rainwater, it is also equipped with LCD touch screen, in order to facilitate the operation of equipment and display feedback information. Tunnel PLC can collect real-time information of various mechanical and electrical facilities, and transmit the collected information to the monitoring center. The monitoring system can maintain normal and stable operation without the impact of communication interruption.
The application of small-sized PLC in automatic control system of rainwater pump has the advantages of simple structure, convenient programming, complete functions, low failure rate, safety and reliability, etc. If the control mode needs to be changed, no wiring need to be changed, only the internal procedures need to be changed to meet different control requirements; when the failure occurs, there are obvious instructions and convenience.
Search, fully realized the purpose of maintenance-free and less maintenance; can also be on-site automatic control and remote control, to achieve unattended conditions, played an important role in Dushu Lake Tunnel.