Study On The Effect Of Moisture Content On Electrical Characteristics Of Natural Ester Insulating Oil

Natural ester insulating oil has replaced traditional mineral insulating oil and become an excellent environmentally friendly liquid insulating dielectric.when building a friendly green power grid.Because of its many advantages such as green environmental protection,renewable,high ignition point,natural degradation,etc.,it has been widely used in offshore wind power transformers,mines and places with high security standards.Therefore,it is of great significance to explore the influence law of the water content of natural ester insulating oil on its electrical characteristics under low temperature environment to the limit capacity and operation reliability of new green transformers.In this paper,FR3 insulating oil is selected as the research object.First,an intelligent electrical insulation test system is designed and constructed,and a batch of qualified natural ester oil samples with different water content are prepared;the electrical performance experiments of natural ester oil under different low temperature conditions are mainly carried out.Data analysis shows that the influence of the water content on the conductivity and breakdown characteristics of oil samples at different temperatures is as follows:the conductivity of oil samples with high micro water content exhibits a single peak variation characteristic with decreasing temperature,and vice versa.-Periodic variation of the drop;at the same time,the AC and DC breakdown voltages of oil samples with different micro-water content show a trend of decreasing first and then increasing,and obtain their minimum value in a specific range;but with the gradual increase of the micro-water content Increase,the AC and DC breakdown characteristics show a tendency to approach each other.The analysis of the breakdown mechanism of dielectrics shows that the kinematic viscosity of the liquid in the lower temperature range determines the conductivity of the natural ester oil,and the presence of micro water and the kinematic viscosity of the liquid are the two direct factors that affect the change of the conductivity and breakdown characteristics of the natural ester oil..This paper carried out experiments on the relative dielectric constant and dielectric loss factor of oil samples with different water content in low temperature environment,and obtained the change curve of dielectric temperature spectrum of oil samples with different water content,and based on the molecular structure characteristics of natural ester oil,In-depth analysis of the influence of low temperature factors on the macroscopic dielectric properties of oil samples under different micro-water content,that is,as the temperature decreases,the dissipation factor of oil samples with different micro-water content presents a single peak characteristic;micro-water content and relative dielectric constant The change is positively correlated,and the relative dielectric constant slowly increases with decreasing temperature.In this paper,through the frequency domain dielectric spectroscopy experiment,the dielectric spectrum curves of oil samples with different water content and oil-impregnated paper in the frequency range of 10^-2Hz¹0³Hz are obtained respectively.The dielectric response theory is used to clarify the frequency factor to the relative dielectric constant and the medium.The influence law of the loss factor change selects the characteristic frequency bands that can characterize the change of the micro water content in the oil sample and oil-impregnated paper,that is,the oil sample dielectric loss factor curve shows a trend of increasing first and then decreasing in the full frequency range.The loss factor curve shows a decreasing trend with increasing frequency;the relative dielectric constant of oil samples and oil-impregnated paper shows a decreasing trend throughout the measurement frequency range.In this paper,the research results of the effect of the micro water content of natural ester insulating oil on its electrical characteristics under low temperature environment can provide a certain technical reference for the design of the new generation of green transformer capacity and an evaluation method for the service status diagnosis of natural ester insulating oil.