Electric Field Distribution Regulation Technology In High-Voltage DC Insulation Based On Organic Regulators

High-voltage flexible DC transmission is the main trend of power grid development in the future.High-voltage DC cable is one of the key power equipment,and the problem of electric field distortion in the insulation structure is the bottleneck for the development of high-voltage DC cables to higher voltage levels.Traditional technical approaches often take specific measures for specific factors that cause distortion of the electric field distribution,and have their own limitations.In order to overcome the limitations of traditional technical measures and increase the electric field dependence coefficient of insulation conductivity,this paper proposes the electric field distribution regulation technology in high-voltage DC insulation based on organic regulators,which directly takes measures against the problem of uniform electric field distribution.More importantly,it has a uniform effect on the electric field distortion caused by any factor,and has a good ability to regulate the electric field adaptively.Therefore,it is of great theoretical and engineering significance to study the electric field distribution regulation technology in high-voltage DC insulation based on organic regulators.Firstly,an organic electric field distribution regulator,polyethylene oxide ether,was selected.In order to verify the effect of adding organic regulators on the dielectric properties of the semiconducting layer,the inner shield-insulation-outer shield three-layer structure of the actual cable was simulated.Polyethylene oxide ether was separately added to the semiconducting layer and the insulating layer for comparative analysis,and the dielectric properties of the sample and the molecular migration effect of the polyethylene oxide ether were explored by dielectric spectroscopy and infrared spectrum.The experimental results show that the addition of polyethylene oxide ether in the semi-conductive layer,the greater the mass fraction added,the larger the ether-based index,but the smaller the increase.the dielectric coefficient due to the test system error,the sample thickness,the semi-conductive layer itself and other factors,so there is no obvious change law;the smaller the molecular weight added under the same mass fraction,the larger the dielectric constant and the larger the ether-based index.Adding polyethylene oxide ether to the insulating layer,the larger the mass fraction added,the larger the dielectric coefficient and the ether-based index,and the larger the increase than the semi-conductive layer;the smaller the molecular weight added under the same mass fraction,the larger the dielectric constant,the no significant change in the ether-based index.Secondly,in order to verify the effect of pre-electric stress on the migration of polyethylene oxide ether molecules,the effect of semi-conductivity on the test was eliminated,and the semi-conductive layer was removed and changed to a single-layer insulation sample.The polyethylene oxide ether was placed in a tube and inverted on a single-layer insulating sample,and a DC high voltage of 3 kV was applied to the entire sample.The migration of the polyethylene oxide ether molecule was analyzed by dielectric spectroscopy and infrared spectrum.The experimental results show that the application of pre-electric stress promotes the migration of polyethylene oxide ether molecules,and the promotion effect increases with the increase of duration and the decrease of molecular weight.This suggests that it is feasible to regulate the electric field by adding an organic regulator to the shielding layer.Finally,the addition of polyethylene oxide ether has a good adaptive uniform ability in the electric field distribution in the insulation structure has been explored.the space charge test of the flat structure sample was carried out for 12 h and 34 h by electroacoustic pulse method.The maximum electric field distribution information is extracted from the data.The experimental results show that the addition of polyethylene oxide ether has a good uniform effect on the electric field distribution distortion caused by the internal space charge of the insulation,and the uniform effect is further improved with the increase of the pressurization time,but the space charge will increase in the later period,and there is a long-term stability problem.