In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calcu...In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calculated with finite element method for field simulation.Tests on artificial pollution insulators are conducted to study the 50% withstand voltage U50 of artificial pollution suspension insulators under different NSDD(non-soluble deposit density)and asymmetric pollution on the top/bottom surface,and study the change of leakage current with air humidity under different voltage and different ESDD(equivalent salt deposit density).The result shows that asymmetric top/bottom surface pollution has a greater impact on the insulator electrical field distribution,and the leakage current will jump under low air humidity,if had large ESDD,which has practical meanings to the anti-pollution design of the transmission line under different pollution levels across the country.展开更多
For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electr...For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electric field distortion, trend to trigger surface discharge of barriers. This paper studied the influence of surface charge on flashover voltage of oil-impregnated pressboard under AC-DC combined electric field. The study finds that the flashover voltage of oil-pressboard interface under negative polarity DC superimposed AC electric field is higher than that.of positive DC superimposed AC voltage to form composite electric field. It was found that homopolar surface charge has been accumulated on the interface of oil-pressboard with positive or negative DC voltage through measuring surface potential by the electrostatic capacitive probe. The surface charge produced electric field in the opposite direction, which weakening the synthetic electric field strength. What＇s more, under the same conditions, the negative surface charge density oil-pressboard is much larger than the positive.展开更多
A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prep...A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.展开更多
为研究盆式绝缘子在电热耦合场作用下瞬态表面电荷分布,建立水平布置的直流气体绝缘输电线路(direct current gas insulated transmission line,DC-GIL)三维几何模型,采用有限元方法研究电导率对DC-GIL绝缘子电荷积聚特性的影响。结果表...为研究盆式绝缘子在电热耦合场作用下瞬态表面电荷分布,建立水平布置的直流气体绝缘输电线路(direct current gas insulated transmission line,DC-GIL)三维几何模型,采用有限元方法研究电导率对DC-GIL绝缘子电荷积聚特性的影响。结果表明:随着体积电导率的增大,由于绝缘子的体传导机制的促进作用,凸表面电荷密度逐渐由负极性电荷转变为正极性电荷。而随着表面电导率的增加,由于主导电荷积聚的传导机制由表面传导向体传导过渡,凸表面电荷密度逐渐由正极性电荷转变为负极性电荷。在气体绝缘输电线路(gas insulated transmission line,GIL)运行时,电流流过中心导体,在GIL和绝缘子内部产生焦耳热,并建立空间分布的温度梯度。由于绝缘子的电导率随温度的变化而变化,在直流电压作用下,绝缘子的电场分布受到影响,进而影响电荷分布。因此,在评估DC-GIL绝缘子的绝缘性能时,应重点考虑体积和表面电导率的影响,对长期运行的绝缘子评估时还应考虑温度梯度的影响。展开更多
基金Project Supported by Key Technology Research Programof SGCC(SGSC[2005]115)
文摘In this paper,the electrical fields along the insulator surface under different scenarios,such as asymmetric pollution on top/bottom surface,and uneven circumferential distribution of surface pollution,have been calculated with finite element method for field simulation.Tests on artificial pollution insulators are conducted to study the 50% withstand voltage U50 of artificial pollution suspension insulators under different NSDD(non-soluble deposit density)and asymmetric pollution on the top/bottom surface,and study the change of leakage current with air humidity under different voltage and different ESDD(equivalent salt deposit density).The result shows that asymmetric top/bottom surface pollution has a greater impact on the insulator electrical field distribution,and the leakage current will jump under low air humidity,if had large ESDD,which has practical meanings to the anti-pollution design of the transmission line under different pollution levels across the country.
文摘For converter transformer, AC-DC combined electric field can trigger space charge accumulation on oil-impregnated pressboard interface. The accumulation of space charge on oil-pressboard interface can result in electric field distortion, trend to trigger surface discharge of barriers. This paper studied the influence of surface charge on flashover voltage of oil-impregnated pressboard under AC-DC combined electric field. The study finds that the flashover voltage of oil-pressboard interface under negative polarity DC superimposed AC electric field is higher than that.of positive DC superimposed AC voltage to form composite electric field. It was found that homopolar surface charge has been accumulated on the interface of oil-pressboard with positive or negative DC voltage through measuring surface potential by the electrostatic capacitive probe. The surface charge produced electric field in the opposite direction, which weakening the synthetic electric field strength. What＇s more, under the same conditions, the negative surface charge density oil-pressboard is much larger than the positive.
基金supported by National Science Fund for Outstanding Young Scholars of China (No. 50625721)
文摘A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.
文摘为研究盆式绝缘子在电热耦合场作用下瞬态表面电荷分布,建立水平布置的直流气体绝缘输电线路(direct current gas insulated transmission line,DC-GIL)三维几何模型,采用有限元方法研究电导率对DC-GIL绝缘子电荷积聚特性的影响。结果表明:随着体积电导率的增大,由于绝缘子的体传导机制的促进作用,凸表面电荷密度逐渐由负极性电荷转变为正极性电荷。而随着表面电导率的增加,由于主导电荷积聚的传导机制由表面传导向体传导过渡,凸表面电荷密度逐渐由正极性电荷转变为负极性电荷。在气体绝缘输电线路(gas insulated transmission line,GIL)运行时,电流流过中心导体,在GIL和绝缘子内部产生焦耳热,并建立空间分布的温度梯度。由于绝缘子的电导率随温度的变化而变化,在直流电压作用下,绝缘子的电场分布受到影响,进而影响电荷分布。因此,在评估DC-GIL绝缘子的绝缘性能时,应重点考虑体积和表面电导率的影响,对长期运行的绝缘子评估时还应考虑温度梯度的影响。
