Application Research Of 500kV Transformer Cooling System Based On PLC And Frequency Conversion Control Technology

As an important component to ensure the safe and stable operation of transformer,the cooling system of transformer has been paid more and more attention by engineers and technicians.Because the cooling control system of transformer put into operation in the early stage is the traditional relay control mode,it has the advantages of low intelligence,high energy consumption and high noise.Aiming at the practical problems of aging and frequent failures of the cooling control system of 1 Main Transformer in 500kV Suihe station,this paper proposes a 500kV transformer cooling system based on PLC and frequency conversion control technology.According to the load,temperature and other parameters,the operation state of the fan is intelligently set,which can significantly reduce the failure rate,energy consumption and noise of the cooling system.The specific work is as follows:①According to the internal heat dissipation mode of transformer,the calculation method of internal heat dissipation of transformer under three conditions of heat conduction,convection and radiation is analyzed,and the temperature rise calculation method of internal winding,core and transformer oil of transformer is studied,which provides corresponding theoretical basis for subsequent system setting.②The hardware part of the main electrical circuit of the cooling system is designed,and the hardware part is connected according to the system control principle block diagram.The focus is to select the Siemens series of signal acquisition and control module to design the main electrical circuit controlled by PLC.By adjusting the frequency to obtain different motor speed,the PLC+frequency conversion control mode is finally realized.In addition,on the basis of retaining the power frequency control mode,the conversion electrical connection circuit of the cooling system dual-mode control system(the control method combining PLC+frequency conversion control mode and power frequency control mode)is designed.③PLC programming software is used to complete the software design of air cooling control system.In order to facilitate the daily operation of the field staff,the PLC+frequency control mode is named "automatic mode" and the power frequency control mode is named "manual mode" in the software interface setting.The software conversion program of dual-mode control system is designed.In case of PLC power failure or all coolers failure,the system changes from automatic mode to manual mode.According to the system operation principle of normal cooling system and cooler failure,the automatic mode operation program is designed and completed,and the overall system control program and the upper computer interface design are completed.④The power saving amount of 12 months is collected on site,and compared with the power consumption under the previous conventional mode,it is verified that the energy saving effect of the system is more significant.The monitoring noise data in different operation states and positions prove that the system has a significant noise reduction effect compared with the traditional power frequency mode.