Study On The Measurement And Control System Of 4 Set Magnetic Switchgear In Underground 1140V Distribution Network

With the rapid development of mining automatic technology, electrical equipments in underground distribution networks tend to become large-scale, HV level, continuous operation and automatic control, which consequently raised higher and higher requirements to fulfill the protection and control of large loads. Combined magnetic switchgears are electrical equipments which could carry out the function of centralized control and protection of the loads, such as shearer, armoured flexible conveyor, crusher and stage loader in fully mechanized heading faces. Meanwhile, the performances of electrical equipments do directly bring serious effects on the continuity of power supply as well as the reliability and security of the electromotor operation. For a long time, single magnetic starter used in underground existed serious problems, such as simple in protection principle, low in reliability and worse in stability, which severely limit the development of domestic coal industry. It, therefore, is great important in practice and high value in application to develop the measurement and control system of combined magnetic switchgears.The emphasis in this thesis is put on the realization of centralized control and integrated protection of electromotors in fully mechanized working faces to overcome the disadvantages of domestic single magnetic starters. The measurement and control system of 4 set magnetic switchgear based on AC sampling in underground 1140V distribution network has been developed, which is equipped with complete protections, reliable performances and intuitionistic display interface. The main works have been done as follows:According to the field condition and requirements of measurement and control system, the general scheme has been proposed, the CPU control system has been designed and the technical targets have been established. In accordance with the practical operation of magnetic switchgears, the ordinary faults of controlled loads and the variety of the electric parameters have been comprehensively analyzed, the protection principles are put forward and the selective leakage protection scheme based on zero-sequence power direction is proposed.Main control and protection system based on SIEMENS CPU226 has been developed to complete the reliable protection of controlled loads.Signal sampling system controlled by Intel 80C196KB has been designed, at the same time, block design method is adopted to compile the program. Based on Fourier algorithm, the modified current algorithm which could effectively eliminate the influence of attenuation DC quantity is brought forward, at the same time, the calculation procedures according to AC sampling has been worked out.In accordance with the display requirements, the display system has been completed, besides, the hardware circuit has been designed, the communication protocols and the software flow have been worked out as well.It has been proved by experiments that the measurement and control system is stable in operation and reliable in function, in addition, its technical specifications have fully met the requirements proposed in this thesis.