Study On Dielectric Response Characteristics Of Oil-Paper Insulation System

Transformer plays an important role in the safe operation of power system.Transformer faults are mostly caused by mineral oil-paper insulation system failures because of mineral oil's problems,so it is necessary to find a new type of insulation oil which can replace mineral oil.Plant insulation oil is a new type of environmental insulation oil,which has the advantages of high ignition point,high biodegradation rate and high dielectric constant.However,there are various kinds of plant insulation oils,and the triglycerides of each kind of plant insulation oils are different,and their physical and chemical properties are quite different.The comparative analysis of the relevant characteristics of various plant insulation oils is helpful to promote their better application.As a non-destructive diagnostic method,dielectric response technique is widely used in transformer insulation diagnosis.Therefore,this paper studies the dielectric properties of representative plant insulating oil and its oil-immersed board,and provides scientific data support for its application in transformer.The dielectric properties and power frequency breakdown characteristics of soybean oil and palm oil were studied.The effects of temperature on the relative dielectric constant,dielectric loss factor and volume resistivity of soybean oil and palm oil were studied.The breakdown voltage of plant insulation oil at different temperature was studied.The binding behavior of plant insulating oil on water molecules at low temperature was studied by means of molecular simulation.Then soybean oil and palm oil board were studied.The dielectric loss factor,complex capacitance et al were studied from the aspects of high temperature,low temperature,temperature change mode,insulation structure and moisture.The results show that the dielectric properties and breakdown properties of the two plant insulating oils are different at different temperatures.Compared with soybean oil,palm oil has higher relative dielectric constant,higher dielectric loss factor,lower volume resistivity and lower power-frequency breakdown voltage.Soybean oil has better dielectric properties and breakdown properties.The permittivity of the two kinds of plant-insulated oil-impregnated paperboard is basically the same under different temperature,temperature change mode and moisture.Compared with soybean oil impregnated board,palm oil impregnated board has a higher medium loss factor on the whole.The temperature change mode has a greater influence on the medium loss factor of palm oil impregnated board.Through molecular dynamics simulation,the dielectric properties and breakdown properties of two kinds of vegetable oils and their oil-impregnated paperboards are mainly related to the micro-parameters such as mean square displacement,dipole moment,polarization strength and free volume.