Study On Measurement And Control System For Vacuum Magnetic Switchgear Based On Programmable Logic Controller

The research project in this thesis is a part of "Study on flameproof and intrinsically safe intelligent vacuum magnetic-switchgear (FISIVMS)" (No.20002013), which is aimed at solving the key problems of centralized control and integrated protection of high capacity motors in high yield and efficiency automation coal faces and sponsored by Education Committee, Science and Technology Committee of Shanxi Province. By analyzing the limitations of magnetic-switchgear at present, a novel intelligent combined switchgear measurement and control system is developed based on programmable logic controller(PLC). Many protective and monitoring functions are integrated in the system, such as pilot circuit monitoring, earth-fault monitoring, short circuit protection, over-load protection, phase symmetry and phase loss monitoring, over voltage protection, under voltage protection, motor thermal monitoring and so on. All measuring results, fault states, fault parameters and error messages of six motors controlled by the system are sent to the liquid crystal display module via the existing serial data connection.First of all, the development history and present situation of FISIVMS are reviewed, the significance and importance to develop the measurement and control system(MCS) of FISIVMS are also introduced. In addition, the function specifications, control principle and technical requirements are put forward and the control strategies and methods of MCS are drawn up in this thesis.According to the safety requirements of underground electrical equipment, an excellent intrinsically safe pilot circuit is designed, the fault characteristics and protection principle of asynchronous motor with single speed and double speed used in underground are simultaneously analyzed, the function parameters corresponding to the fault protections for high capacity motors are determined. At the same time, module program design method and compiled monitoring program and function subprograms are emphatically described. Especially, more attention is paid to the design philosophy, operation principle,hardware block diagram and software flow chart of MCS.From the actual cases of underground electrical distribution networks, the interference sources and features of interference signals in industrious environment are discussed. Besides, anti-interference measures by use of hardware and software are taken to eliminate interference singles in this paper.The measurement and control system based on PLC, combined with new protective theory and signal-sampling circuit consisted of large-scale integrated circuits, has been developed last year. All performance and feature parameters are all satisfied the technical requirements proposed by research application. It has been proved by preliminary field tests that the system with its application programs is more utilizable, reliable and safety than other traditional protective systems.