Design Of Detector For SF₆ Gas Decomposition

In recent years,SF₆ gas-insulated equipment has been widely used in the power system to satisfy t he developing demands of the power industry.However,there will be partial discha rge and overheating in the equip ment during the long te rm running.SF₆ is easy to decom pose under such environment,which will result in malfunction of SF₆ gas-insulated equipment.In order t o reduce the m alfunction rate,people investigate deeply about decomposition phenomenon.Researches show that it is feasible to judge the early failure of SF₆ gas-insulated equipment by analyzing the decom position products of SF₆.Thus,accurate detection of internal gas composition of SF₆ is of great significance to predict the status of SF₆ gas-insulated equipment.In this paper,the detector for SF₆ gas decomposition is designed.Since electrochemical gas sensor has fast response speed and high sensi tivity,electrochemical method is used to detect the concentration of SF₆ decomposition products（CO,SO2,H2S）.The detector includes software and hardware system.The software system is m ainly composed of control program and data processing program.C language is used to program.The modular design of the source code ensure s the stability and flexibility of the software system.Th e hardware system is com posed of signal acquisition module,signal proc essing module,microcontroller unit,external storage module,output module and power supply.The electrochemical sensor is the core device of the signal acquisition m odule.It converts the concentration of the gas to be measured into a weak current signal and output s it to the signal processing module.The signal processing module amplifies the weak signal,converts it into a digital signal and then sends it to the m icrocontroller unit.Then,the data processing program in the microcontroller unit calculates the digital signal.The results are stored in the exter nal storage device and simultaneously output to the LCD screen for the workers to read.In this design,C8051F340 m icrocontroller unit is used as the main chip,and we select AD7794 and A T24C16 as AD c onversion chip and the external expansion memory chip,respectively.Experiment results indicate that the detector has high precision and can be used to analyze in sulation conditions of SF₆ equipment.It has the high application value.