Study On The Measurement And Control System Of 3.3kV Movable Transformer Substation Based On Programmable Logic Controller

The Movable Transformer Substation (MTS) plays hinge role in supplying continuable electrical power energy for coal mining face in the underground 3.3kV distribution networks. The protective system of traditional MTS is made up of schism organs, but framework is complex and reliability is rather bad, which badly impacts the running stability of coal mining face. However, because of slow development of related industry at home, the electrical switchgears in underground 3.3kV distribution networks are mainly imported from foreign countries. The development and popularization of 3.3kV power supply technique in underground distribution networks are badly hindered by the long supply period of the fittings in switchgears and their high price. So it is hence important to develop a new measurement and control system of 3.3kV MTS.The research of the measurement and control system for 3.3kV MTS based on PLC is deeply carried out in this paper as following:1, Aiming at the present operation condition of the MTS in underground at home, multifarious fault causes for it are analyzed systematically and deeply. The traditional differential protective principles of the transformer are used in this thesis. Filter circuit of high precision and narrow band-pass is designed and the differential protection of the transformer is improved. Consequently, the second harmonic is dodged effectively during the normal starting. As a resultthe unexpected trip is reduced and the reliability is increased.2, Based on the analysis of the various principles of the leakage protection, the protective principle with additional direct current power is adopted and the scheme of leakage protection is designed in this thesis. The trip resistance value and closed resistance value of 3.3kV underground power supply system is confirmed by calculating. It has been proved by test results that the symmetric and asymmetric insulation faults in the underground distribution networks can be examined correctly by the scheme of leakage protection. The stability of trip resistance value of the earth leakage fault is guaranteed.3, A novel measurement and control system (MCS) used in 3.3kV MTS has been established based on PLC, by which electrical faults such as earth leakage, over-load, short circuit, over-voltage, over-heat, differential protection and so on can be automatically distinguished and processed.4, The design method of module program is introduced and the monitoring program and function subprograms are compiled in this thesis. Especially, more attention is paid to design philosophy and software flow charts.5, According to the special environment in underground, the sources and the features of interference signals are discussed, and with the exception of this, anti-interference measures are taken to eliminate interference signals from MTS in this paper by use of hardware and software.It has been shown by tests in our laboratory that all performance and feature parameters are all satisfied the technical requirements, proposed by research application, and the measurement and control system is reliable, which is provided with higher applied value.