FIGURE 9 - uploaded by Wang Jingrui
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When DC GIL in operation endures the lightning impulse voltage, the charge accumulation at the gas-solid interface area will seriously affect the insulation performance of the spacer. Considering that gas side conduction is one of the important factors affecting charge accumulation, for the purpose of clarifying of the insulation characteristics of...
Context in source publication
Context 1
... spacer is contaminated by metal particle, unlike the non-contaminated, the pair of bipolar charge appear on the surface, which is shown in Figure 3. Typical flashover trace induced by metal particle are recorded in Figure 9. Because the composite lightning impulse voltage is negative polarity and a large number of homocharges accumulate at the tip near the central conductor, where the local electric field is weakened, discharge will bypass the area. ...
Citations
... Metal particles can distort the electric field at the solid-gas interface and induce discharge. In recent years, scholars believe that metal particles, as the main defect in the gas insulation equipment, are important causes of insulator surface flashover [44][45][46][47]. ...
Under DC voltage, the interface charge of the spacer in gas-insulated metal-enclosed transmission lines (GIL) and gas-insulated metal-enclosed switchgear (GIS) is prone to accumulate, and the charge is an important factor to induce surface flashover. This paper concentrates on the surface flashover induced by solid-gas interface charge accumulation in DC GIL/GIS. Firstly, the electric field distribution of the real insulator and the electrode structure commonly used in research are analyzed and summarized into two distribution forms: the tangential-component dominant type and the hybrid type. According to the electric field distribution forms, how the density distribution and electric field distortion of interface charge influence the flashover voltage of spacer is reviewed, and the influence of metal particles on charge and surface flashover is reviewed as well. Finally, the existing physical models of surface flashover induced by interface charge are summarized.
The advanced Gas Insulated Switchgear/Gas Insulated Lines (GIS/GIL) transmission equipment serves as an essential physical infrastructure for establishing a new energy power system. An analysis spanning nearly a decade on faults arising from extra/ultra-high voltage discharges reveals that over 60% of such faults are attributed to the discharge of metal particles and dust. While existing technical means, such as ultra-high frequency and ultrasonic sensing, exhibit effectiveness in online monitoring of particles larger than sub-millimeter dimensions, the inherent randomness and elusive nature of micron-nano dust pose challenges for effective characterization through current technology. This elusive micron-nano dust, likely concealed as a latent threat, necessitates special attention due to its potential as a “safety killer”. To address the challenges associated with detecting micron-nano dust and comprehending its intricate mechanisms, this paper introduces a micron-nano dust adsorption experimental platform tailored for observation and practical application in GIS/GIL operations. The findings highlight that micron-nano dust’s adsorption state in the electric field predominantly involves agglomerative adsorption along the insulator surface and diffusive adsorption along the direction of the ground electrode. The pivotal factors influencing dust movement include the micron-nano dust’s initial position, mass, material composition, and applied voltage. Further elucidation emphasizes the potential of micron-nano dust as a concealed safety hazard. The study reveals specific physical phenomena during the adsorption process. Agglomerative adsorption results in micron-nano dust speckles forming on the epoxy resin insulator’s surface. With increasing voltage, these speckles undergo an “explosion”, forming an annular dust halo with deepening contours. This phenomenon, distinct from the initial adsorption, is considered a contributing factor to flashovers along the insulator’s surface. The physical mechanism behind flashovers triggered by micron-nano dust is uncovered, highlighting the formation of a localized short circuit area and intense electric field distortion constituted by dust speckles. These findings establish a theoretical foundation and technical support for enhancing the safe operational performance of AC and DC transmission pipelines’ insulation.
In this paper, a 1000 kV gas insulated transmission line (GIL) prototype with a basin insulator and a three-post insulator structure was designed and developed to study the particle motion behavior in an ultra high voltage (UHV) GIL. Particle traps were arranged on the convex side of the basin insulator and near the three-post insulator. Aluminum and copper particles were arranged in front of and on the surface of the traps. A short-time voltage application procedure and a graded long-time voltage application procedure were designed to investigate the difference in the capture effect of the traps on the two types of particles when the test voltage was applied to the prototype through these two voltage application procedures. The results of the study show that the particle motion behavior is complex under AC voltage. The placement of the particles, their own properties and the voltage application procedure all affect the motion behavior of the particles. The trap with the grid structure is effective in capturing particles near both the convex side of the basin insulator and the three-post insulator. At the end of the test, some of the particles went inside the trap and some of them gathered at the edge of the trap. The graded long-time voltage application procedure with a small voltage application gradient and a long duration enables the particles to move sufficiently at a lower voltage to be trapped.
The construction of the future energy structure of China under the 2050 carbon-neutral vision requires compact direct current (DC) gas-insulation equipment as important nodes and solutions to support electric power transmission and distribution of long-distance and large-capacity. This paper reviews China's 10-year progress in DC gas-insulated equipment. Important progresses in basic research and industry perspective are presented, with related scientific issues and technical bottlenecks being discussed. The progress in DC gas-insulated equipment worldwide (Europe, Japan, America) is also reported briefly.
Metal contaminants can distort the surface electric field of the tri-post epoxy insulator and cause serious surface charge accumulation, significantly reducing the insulation performance of the insulator under the superimposed DC and lightning impulse voltage. In this paper, an experimental platform for charge accumulation and surface flashover of tri-post epoxy insulators under the superimposed DC and lightning impulse voltage was built, by surface point measurement and charge inversion calculation, the surface charge distribution characteristics of tri-post insulators with attached particles was experimentally explored and the influence law of attached metal particles on the charge accumulation was discussed. The results show that metal particles can cause a surge in the surface charge density of the tri-post epoxy insulator, forming bipolar charge spots whose polarity is opposite to that of the adjacent electrodes. The adsorbed metal dust can cause the polarity reversal of adjacent surface charges, forming a large-area unipolar charge spot. Moreover, the flashover voltage of a tri-post insulator under DC superimposed lightning impulse voltage with a clean surface and attached metal particle was measured, and the synergistic induction mechanism of charge spot accumulation and metal particle discharge on the flashover along the face of the tri-post insulator is thereby revealed. Compared with the clean insulators, the surface flashover voltages of tri-post epoxy insulators with metal contaminants adhered decrease under the superimposed voltages of different polarities, but the decline amplitude is greater under the heteropolar composite voltage. When adhered to the middle of the insulator leg, the distribution range of bipolar charge spots is the widest, and the surface flashover voltage decreases sharply, which can drop by 32% compared with the absence of particles. In addition, when the metal dust adsorbed by the tri-post epoxy insulator has a wide distribution range, the impact of metal dust on the flashover voltage is greater than that of the attached metal particles, and its hazard cannot be ignored. The research results can provide a reference for the insulation test method and optimal design of the DC tri-post epoxy insulator.
The interpretation of the surface charge pattern of spacers in gas-insulated transmission lines (GIL) is a research topic with great significant importance, which requires a comprehensive understanding of charge behaviors at physical interfaces. Here, we report a surface charging phenomenon of spacers in presence of metal particles inside the direct current (DC) GIL. The charging of spherical metal particle on the spacer surface appears as dotted discontinuously distributed charge spots which are due to the charge injection from the induced charge of the metal particle and gas ionization over the metal particle surface. Concentrically distributed bipolar charge patterns are seen to build up, which are due to the surface trapping of charges from gas ionization at the end tip of the acicular metal particle. The lateral type of ionization obeys the law of dielectric barrier discharge of the needle-plate electrode at an intense DC
electric field, which may bring significant influence on the safety of the spacer. The study in this letter provides direct evidence demonstrating the surface charge patterns of spacers in the presence of metal particles, which serves as an important basis in the design of DC GIL.
