The Research Of The Distributed Measurement System Of Sluice Opening In Hydropower Station

A curved floodgate to release floodwater is one of the important equipments of the hydroelectric power plant. The outdated measuring apparatus of the floodgate's opening has low precision and reliability. The distributed PLC system of the floodgate's opening measuring presented by the paper has many advantages such as high reliable operation, high measuring precision, having the network communication function, convenient installation and correction, etc.This thesis further studies the key device for the floodgate's opening measuring, the rotary encoder, selects the absolute rotary encoder adopting the binary cyclic code, studies the method for transforming the cyclic code to the binary data and according to the transforming formula designs the ladder diagram program.For the users' convenience, users are allowed to install the encoder anyway. In other words, the range used actually of the encoder is allowed to span its zero point, and the ascending direction of the encoder's output and that of the floodgate's opening can be identical or not.No matter how the encoder is located, it can be corrected by inputting the current actual opening data of the floodgate merely.The paper presents a method to calculate the floodgate's opening according to the output of the encoder and derive the corresponding computational formula. The nonlinearity in the floodgate's opening measuring is analyzed and a method for correcting the nonlinearity is proposed.The hardware and external behavior of the human-machine interface of the floodgate's opening measuring apparatus are designed. To guarantee the security of the system, a password is required to be inputted firstly before inputting corrective data and modifying the password.The program of the man-machine interface is designed by the sequential function chart design method The paper presents the sequential function chart of the program. According to the chart the ladder diagram program can be made out easily.The curved floodgate's opening measuring system adopts two-level structure, main control level and field level. The computers to monitor and control the water level belong to the main control level and are used to monitor every floodgate and measure and display the upriver water level. The floodgate's opening measuring apparatus whose core is a PLC, belongs to the field level and is used to implement the data collection of floodgates, calculation, communication, etc. These PLCs are linked one another by the RS-485 network.The communication between computer and PLC adopts the Computer Link protocol. The paper introduces in detail the setting of communication parameters, the basic format of data transfer and the method to perform communication using the Computer Link protocol.