Application of the hottest PLC in the automatic pu

  • Detail

Application of PLC in automatic pumping system of Hongmen hydropower plant introduction in recent years, with the improvement of automation technology in China, factory automation has also reached a new level. Programmable logic controller (PLC), as a new industrial controller developed from the 1980s, is the product of the combination of automatic control, computer and communication technology. It is a field equipment specially used for industrial production process control. PLC has been widely used in various fields because of its unique advantages in small size, complete functions, low price and high reliability. Hongmen hydropower plant is an old power plant that has been put into operation for more than 30 years, and the original automation equipment can not meet the needs of safe production. The spillway is one of the most important hydraulic structures in the hydropower plant, so it is particularly important for the daily operation and maintenance of the building. The renovation of the automatic pumping system of the stilling basin drainage gallery is just to meet this requirement. Taking into account the natural environmental factors of hydraulic structures, according to the principle of reliability first and selecting products with high cost performance, we focused on the comprehensive comparison and selection of PLC series products of AB, Ge, Mitsubishi, Omron, Modicon, Siemens and other companies, and finally selected the products of Mitsubishi because Mitsubishi products have the above advantages, It also has the characteristics of convenient maintenance and simple and intuitive operation. The PLC adopts Mitsubishi fx2n-48mr+2a/d+2d/a, which is mainly responsible for data acquisition of water level and control of start/stop of submersible pump. At the same time, a Mitsubishi 5.7-inch touch screen is selected, which is mainly responsible for parameter display, parameter modification and detailed fault information display

2 system structure

the spillway stilling basin drainage gallery drainage system of Hongmen hydropower plant is mainly composed of three parts. ① Automatic drainage system of first-class weir Gallery; ② Automatic drainage system of secondary weir Gallery; ③ Man machine dialogue system. The main control system is installed in the secondary weir Gallery, which is composed of water level transmitter, liquid level switch, programmable controller, contactor, control switch, etc. In addition to the local control function, it also has the functions of water level detection, real-time display, sensor setting, real-time control and protection through the remote LCD touch display. Only water level transmitter, contactor and other water pump starting equipment are installed in the primary weir gallery. The LCD touch screen, that is, the man-machine dialogue system, is installed in the office of the spillway maintenance personnel, about 100 meters away from the main control center

3 characteristics of working components of each part

3.1 plc

plc (FX2N-48MR) is the core control component of the whole control system. Its rich and complete control operation instructions, superior performance and convenience of field programming and debugging have made it a control equipment welcomed by field technicians. Main performance indicators: 24 point input/24 point relay output, built-in 8000 step ram, usable memory box, and operation speed of 1.52 ц S ~ 100 ц S/step (application instruction); The maximum load of the output contact is 80va or 100kW, and the service life of the output contact is 20va/3million times, 35va/1million times and 80va/200000 times

3.2 2a/d and 2d/a

fx2n-2a/d conversion modules are used to receive the 4 ~ 20 mA current signal represented by ouyangming pair output from the water level transmitter and convert it into decimal number available for PLC program. (i.e. converting analog quantity into numerical quantity) fx2n-2d/a conversion module is used to convert the control quantity value obtained by PLC operation into -1. Use a soft cloth dipped in a little neutral detergent to clean the 0V ~ +10v voltage signal, and input the current analog quantity signal to the remote monitoring system through RS485 or RS422 interface connection

3.3 liquid level transmitter and liquid level switch

the liquid level transmitter adopts the American Mike product with high precision and high reliability, and the model is mpm426w. The liquid level switch adopts Taiwan Fanyi LTB product. When the water level reaches the set value, it gives a programmable action signal

3.4 touch screen

as a new type of man-machine interface, has been concerned since its emergence. Its simplicity, powerful function and excellent stability make it very suitable for industrial environment. Users can freely combine text, buttons, graphics, numbers, etc. to process or monitor and manage information that may change at any time. With the rapid development of industrial equipment, the previous operation interface needs to be operated by skilled operators, which can not improve efficiency. However, the human-computer interface can clearly indicate and inform the operator of the current status of the machine and equipment, making the operation simple and vivid. Using the touch screen can also standardize and simplify the machine wiring, reduce the i/o points required for PLC control, reduce the production cost, and relatively improve the added value of the whole set of equipment. The system adopts Mitsubishi got930 touch screen, which has good commonality with Mitsubishi PLC. It can monitor and modify the program without having to repeatedly plug and unplug the interface

4 the main functions realized by the device system

4.1 have three operation modes: automatic, manual and exit, which are manually switched by the operating handle

4.2 in the "automatic" mode, start and stop the submersible pump according to the liquid level signal provided by the liquid level switch (or liquid level transmitter); Under the "manual" operation mode, the submersible pump can be directly started/stopped by manually operating the handle. In the "exit" operation mode, neither automatic nor manual operation will work

4.3 automatically and regularly switch the main/standby status among the submersible pumps, or manually switch the main/standby status among the pumps

4.4 use led to indicate the operation status and system fault of the device

4.5 LCD is used to display parameters (such as water level, etc.) and modify parameters (such as water level setting values for pump start and stop, pump switching time parameters) and display detailed fault information

4.6 it has fault alarm function. The alarm information includes: power failure, water pump failure, transmitter failure, high water level, low water level, PLC failure, etc

4.7 it has self checking function and strong fault tolerance

4.8 the control power supply adopts ups with AC and DC input

4.9 it has the function of communication link to transmit alarm signals and analog signals to the remote computer monitoring system

5 software design

according to the requirements for the control of the drainage system of the spillway stilling basin drainage gallery, the control program is compiled by using the rich instructions of Mitsubishi PLC, and in combination with the principles of on-site commissioning and optimization of the control program, the control system mainly has the following control program modules

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