The Application Analysis Of Ultrasonic Detection Technology For SF₆ Leakage

SF6 relies on its excellent insulation and arc extinguishing performance,has been widely used in GIS(Gas Insulated Switchgear,GIS).However,it is difficult to avoid leakage due to in the process of manufacture,operation and maintenance of GIS equipment,which leads to the failure of GIS insulation performance,causing environmental pollution and even endanger people's health.Therefore,it is of great significance to study and analyze the SF6 gas leak detection technology.Comprehensive analysis of the advantages and disadvantages of different detection methods,because of its low cost,high efficiency and non-contact measurement,Ultrasonic technology has high application value in the field of detection.SF6 gas leakage detection method based on ultrasonic technology is put forward.The theory of sound velocity measurement of binary-gas composition is deduced and demonstrated,which is also compared with acoustic attenuation gas detection theory.After detailed demonstrate and compare the different detection model on the basis of sound velocity measurement of binary-gas composition,Dual channel differential phase detection model is determined,and the corresponding phase difference signal detection method is given.The feasibility of SF6 gas leak detection is further proved by Matlab numerical simulation.In this paper,the overall scheme of SF6 leak detection system is designed based on the detection model.The influencing factors and Key technologies of ultrasonic gas detection in the application process are studied.The impacts on measurement are mainly analyzed from the perspective of ultrasonic signals,disturbing objects,environmental factors and phase acquisition.On this basis,the Key technologies of ultrasonic transducer driving,testing chamber development,ultrasonic signal processing and phase difference detection in system design are also described in detail.The hardware and software platform for SF6 gas leak detection system based on ultrasonic technology is designed.By the cooperation of ARM and CPLD chip,the signal acquisition and processing are completed.Specific description is as follows:CPLD chip produces pulse signal to drive the ultrasonic transducer;Design signal conditioning circuit for ultrasonic echo signal processing;Detection of weak phase difference between two ultrasonic echo signals by using CPLD digital chip;ARM chip completed the collection of oxygen,temperature and humidity and SF6 concentration.PC software achieved the visual interaction,the system centralized control,storage,historical query,alarm and also completes the communication with the collector through RS485 protocol implementationFinally,the system is debugged through different modules,Error analysis of the detection system was done from perspective of theoretical and practical design.The cause of the measurement error in the theoretical model is deduced,and the errors caused by different factors are analyzed and calculated.The gas concentration calibration system is designed to test the SF6 leak detection system,the calibration and correction of the data are also completed.The measured results show that the system detection error can be controlled within 100ppm,which can meet the requirements of SF6 leakage measurement in GIS equipment.