Design Of The Measurement And Control System In 3.3kv Combined Switchgear With Six Branch Based On Master-slave Structure

The content of this paper is an important part of "key technologies of intelligent combination electrical equipments for coal mining safely and efficiently" (2007BAB13B01), which is sponsored by the National Key Technology R&D Program of China during the Eleventh Five-year Plan Period. The work is propsed to solve the problem of low intelligent grade, poor safe reliability and control decentralization of electrical control technology used in full-mechanized high production and efficiency coal face. With the increasing power and rising voltage of fully-mechanized mining equipments and widely application of 3.3kV running voltage level, the requirements of security and reliability of electrical equipments are getting higher and higher. At present, the domestic 3.3kV combined switchgear with the core of PLC has high reliability and plays a positive role in promoting the localization of 3.3kV electronic control devices, but it can only execute direct current sampling, which has disadvantage of complex constructure, large volume, low sampling precision and poor real-time. Measurement and control system of combined switchgear based on MCU has been developed in abroad which greatly improves performance of combined switchgear. But the imported products also have following disadvantage, such as expensive value, long supply cycle and uneasily purchased fittings etc, which restrict the popularity of 3.3kV high production and efficiency coal face. As a result, the research of 3.3kV combined switchgear based on master-slave structure has important practical significance.With the development of computer control technology, there are many new micro-controllers with high operation speed, high reliability which are superior to PLC. The MCU has been applied to 3.3kV combined switchgear and the measurement and control system of 3.3kV combined switchgear based on multi-CPU master-slave structure is designed in this paper. The superior and lower subsystem run together and each performs its functions. In this system, the superior subsystem using singal chip as its CPU perform the functions of keyboard input, system parameters display and man-machine communication. The lower subsystem with the CPU of DSP perform the function of data collection, data processing and protection. The prototype is developed and performance is tested in this paper. All targets reach the design requirements and meet the requirements of safe, reliability and efficiency in the mechanized coal face. Main contents are as follow:According to the present research in worldwide and developing trend of combined switchgear, the whole project of combined switchgear that meets the load control requirments of full-mechanized coal face is put forward, the system specifications are determined and proper master-slave CPU and AC sampling chip are selected.The causes and electrical characteristics of leakage fault, current type of fault and voltage type of fault underground are analyzed, and the method of fault protection which provided the basis for system protection is proposed.Pliot circuit based on locked relay is proposed which overcomes the self-start phenomenon of load;AC sampling system based on high resolution sampling chip is designed which improves measuring real-time and precision; Temperature detection circuit baesd on XTR105 is designed to overcome the error caused by platinum resistance and resistance of lines.Interface between human and LCC which adopted color LCD screen and 4×4 matrix keyboard is proposed. Friendly interactive interface is designed, which would enhance maneuverability, decrease the time of fault detection and troubleshooting, and boost productivity.According to system requirements, the communication mode between Superior subsystem and lower subsystem as well as between superior subsystem and LCD screen are formulated which ensure the reliability of data transmission. The program of the superior subsystem and lower subsystem are compiled by modular programming method which would be convenient for system to develop and debug, shorten the scan period of program, and improve the system efficiency.Software and hardware of measurement and control system in 3.3kV combined Switchgear are debugged on the experimental platform in laboratory. The results indicated that the faults of load and power grids can be detected by the system accurately, quickly and reliably, the protective action is sensitive and reliable, and the interaction of interface between human and LCC is excellent. Anyhow the requirements of safety work under mine can be meet suitably.