Experimental Reaserch On Physical And Chemical Properties Of Transformer Oil Containing Particulate Contaminant

In the process of production, transportation and operation, the transformer oil is very easy to be mixed with particles, water and other pollutants which will affect the physical and chemical properties of the oil. And different particle size, content of the particles in the oil, the degree of the deterioration is also different. So the study of the main physical and chemical properties changing of the transformer oil containing contaminant particles and different content and different particle size of particles on the performance of transformer oil influence to master the performance of transformer oil deterioration and ensure equipment safety operation has an important significance.First, 24 groups of oil samples with different particle sizes of copper, iron, and silicon dioxide were made by Uniform design method based on ISO4406 standard. And the particle size distribution of oil samples containing three kinds of particles were tested respectively; Then it has achieved the change rule of the key physical and chemical properties were influenced by the particle content according to making Physical and chemical performance index tests of electrical properties（breakdown voltage, dielectric loss factor）, flow properties（kinematic viscosity, surface tension,pour point, freezing point） and chemical properties（acid, oxidation stability）. The change law of the key physical and chemical properties were influenced by the particle content.Second, according to the test data, the mathematical model of copper, iron, and silicon dioxide particles with different particle size, particle content and the key physical and chemical properties of oil samples were established by Takagi-Sugeno fuzzy principle, support vector machine and partial least squares method. The influence laws of different component and particle content on the physical and chemical properties of oil were obtained according to test the performance of the properties.The established models obtained excellent forecasting results.Finally, the influence of different particle sizes and different contents of Cu, Fe and SiO₂ particles on the key physical and chemical properties of oil was analyzed based on the prediction model of physical and chemical properties of the transformer oil. The contamination of copper and iron metal particles in the range of 5-25μm has a significant influence on the breakdown voltage of oil, and the change fluctuation and the values of the breakdown voltage of oil samples with non-metallic particles were larger than those of the oil samples with metal particles; The particle sizes of copper, iron, and silicon dioxide particles which have a significant influence on the dielectric loss factor of oil are 5 and 15μm. The change ranges of dielectric loss factor values of oil are0.021%、0.019%; The particle sizes of copper, iron, and silicon dioxide particles which have a significant influence on the kinematic viscosity of oil are 15 and 25μm. The change ranges of kinematic viscosity values of oil are 0.455mm2/s、0.56mm2/s; The particle sizes of copper, iron, and silicon dioxide particles which have a significant influence on the surface tension of oil are 5 and 15μm. The change ranges of surface tension values of oil are 0.067 m N/m, 0.042 m N/m. The particle sizes of copper, iron,and silicon dioxide particles which have a significant influence on the pour point of oil are 5 and 25μm. The change ranges of pour point values of oil are 10℃,8.2℃. The particle sizes of copper, iron, and silicon dioxide particles which have a significant influence on the freezing point of oil is 5μm. The change ranges of freezing point value of oil is 20 ℃.The acid values of the oil containing silicon dioxide after thermal oxidation are less than the oil samples’ containing metal particles. The contamination of metal particles in 15μm has a significant influence on the oxidation stability of oil, and the change range is 0.066 mg KOH/g.