Study On The Characteristics Of Gas Sensor For Chromatographic Analysis Of Transformer Oil

As the most accurate and effective diagnostic method for transformer fault diagnosis,dissolved gas in transformer oil analysis is widely used in the work of the national grid.Gas sensor detection technology is one of the most key technologies in the analysis of dissolved gas in oil,and is based on gas sensitive materials.SnO₂,one common gas sensitive material,has the advantages of low cost,simple process,but it can't meet stability,accuracy and sensitivity requirements in the relatively harsh working conditions of electrical work,therefore,it is necessary to carry out a large number of experimental improvements to the SnO₂ sensor.Metal doping is a very effective way.In this paper,the SnO₂ sensor is studied from the theoretical analysis to the experimental preparation,and the obtained sensor is applied to the chromatograph.Based on the density functional theory and the first-principles theory,the relaxation structure on Sn surface of SnO₂ is studied,and a metal silver and copper doped SnO₂ model is established by cutting SnO₂ unit cells.On the basis of this,the different adsorption energies of hydrogen on pure SnO₂ and metallic silver and copper doped SnO₂ are studied.It is concluded that the metal doping favors the adsorption of hydrogen.When the silver is doped,the adsorption capacity of the corresponding hydrogen is the largest and the charge transfer amount is the most.The conductivity of the model after doping is the smallest,which narrows the forbidden band,significantly improves the sensitivity of the sensor.The nanometer microspheres doped with SnO₂ were prepared by hydrothermal method,and the particles with uniform dispersion were obtained.The morphologies are characterized by SEM and HRTEM.It is found that silver doping dose not change the basic morphology of SnO₂.Metallic silver doped SnO₂ is prepared as a sensor and it is tested on the gas-sensitive platform of the laboratory.It shows that in different concentrations of hydrogen environment,the sensitivity has also undergone significant changes,and the sensitivity and concentration have a clear linear relationship.It is found that silver doping can enhance the stability of SnO₂ sensor by studying its response-recovery time.When the sensor is in the air,the sensor can quickly return to the fixed resistance.Using the metal silver doping SnO₂ sensor on the portable chromatography,designing the sensor package,testing the actual carrier gas and test gas of the sensor,this thesis provides a basis for further practical application of the sensor,and offers a way of thinking for the transformer charged detection.