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

The 3.3kV Mobile Transformer Substation (MTS) is one of the key electrical apparatus in the 3.3kV underground distribution networks, which plays important role in supplying and transforming electrical power energy. Traditional MTS cannot meet the needs for high production and high efficiency of fully mechanized coal mining face due to its inherent defects. It is hence important to develop a new measurement and control system with high significant for MTS.The research of the measurement and control system for 3.3 kV MTS based on PLC is deeply carried out in this paper as following:Aiming at the present operation condition of the power transformer applied in the MTS in underground in our country, fault causes for the power transformer are analyzed systematically and the traditional protective methods of the transformer are improved in this thesis. At the same time the second harmonic is dodged effectively during the normal starting. As a result the unexpected trip is reduced and the reliability is increased.Based on the analysis of the advantage and disadvantage of the leakage protection in the 1140V underground power supply system and in accordance with the special needs of 3.3kV underground power supply system, the scheme of earth leakage protection on the basis of principle with additional direct current detection is designed by which the symmetric and asymmetric insulation faults in the underground distribution networks can be examined correctly. In addition, the tripping insulation resistance value and lockout insulation resistance value are determined and the stability of trip resistance value of the earth leakage fault is guaranteed.A novel measurement and control system (MCS) used in 3.3kV MTS has been established based on PLC. By which these electrical faults, such as short circuit, over-load, over-voltage, phase open, earth leakage and so on, can be automatically distinguished and processed. Both the electrical parameters andthe fault reason can be displayed on the big liquid crystal screen, which can save the time in getting rid of the fault and improve the production efficiency.Finally, according to the special environment in underground, the sources and the features of interference signals in underground environment are discussed; With the exception of this, anti-interference measures by use of hardware and software are taken to eliminate interference signals from MTS in this paper.The measurement and control system for the 3.3kV MTS has been tested in the laboratory, electrical parameters has been measured and the protection p.. rformance is proved. It has been shown that this protective system is stable, reliable and is of great-applied value in mining industry.