Metal particles on the epoxy insulator of gasinsulated switchgear (GIS) have been considered as a critical factor leading to severe surface charge accumulation. This paper reports on the charge distribution behavior on a downscaled insulator in heptafluorobutyronitrile C 4 F 7 N and carbon dioxide CO 2 mixture with a linear metal particle under AC voltage. In this study, the metal particle was placed on the grounded electrode, the high-voltage electrode, and the middle area of the insulator surface, and a case without metal particle was implemented. The potential measurement device scanned the insulator surface at 20,40, and 60 minutes of applied voltage and the obtained potential were converted into charge density by the inversion algorithm. The results showed that the surface charge on the insulator was mainly negative and the shape of the charge distribution was almost unchanged as time increased. However, the characteristics and polarity of the charge speckles varied when the metal particles were placed at different positions on the insulator surface.
In this paper, the aramid fiber surface was modified by plasma, and the effects of plasma on the interfacial properties of aramid fiber reinforced epoxy resin (AFRP) was studied. The shear strength between aramid fiber and epoxy resin is notably enhanced after undergoing plasma treatment. Additionally, the AC breakdown strength of the treated samples can reach up to 33.2 kV/mm, which is 13.7% higher compared to the untreated samples. After treatment, the conductivity and dielectric constant of the samples decreased to some extent within a certain range. When compared with untreated samples, this provides a method to enhance the interfacial properties of aramid fiber reinforced epoxy resin composites. This could be a valuable development for using such materials in HV (high voltage) electrical equipment.
The ultra-high frequency (UHF) method has found widely application in the field of partial discharge (PD) detection in gas insulated switchgear (GIS). UHF sensor is an essential component and whose performance highly correlates with the effectiveness of PD detection. In this paper, a microstrip antenna is designed as a new UHF sensor for PD detection by adopting coplanar waveguide feeding. The geometric model is firstly established based on electromagnetic theory. The key dimension parameters are optimized considering the demands of PD detection. A trident-shaped feeding strip is loaded to further enhance the sensor performance. Obtained results demonstrate that the working band of the proposed UHF sensor is 500-1120 MHz with an acceptable size, while the radiation characteristics are good with a peak gain of 4.6 dB. PD experiments are carried out for two typical artificial defects of corona and internal air-gap discharge to verify the effectiveness of the designed sensor. It is indicated that the sensor can effectively detect PD signals, and is expected to be used for PD detection in GIS.
Polypropylene (PP) insulation material displays higher melting point, high breakdown strength and volume resistivity, which meets the needs of high voltage cable insulation in the future. This paper focuses on the influence of crystallization characteristics on the resistant performance of electrical tree of polypropylene (PP). The sample of PP insulation are non-isothermally crystallized at different cooling rate and isothermally crystallized at different temperatures. The spherulite size of PP insulation samples decrease with the increase of cooling rate. The electrical tree of the sample cooled with a rate of 10 K/min has short trunks and many branches. While as the cooling rate slowed down and the spherulite size increased, the electrical tree branches decreased, the length increased, and the electrical tree deterioration increased. It is found that the electric tree tends to grow along the spherical crystal boundary.
Based on the density functional theory, the interaction between the decomposition products of $\mathrm{C}_{4}\mathrm{~F}_{7}\mathrm{~N}/\mathrm{CO}_{2}$, a new type of environmental protection insulating gas, and epoxy resin monomer was studied from the microscopic point of view. The potential adsorption sites of $\mathrm{C}_{4}\mathrm{~F}_{7}\mathrm{~N}/\mathrm{CO}_{2}$ mixture decomposition products and epoxy resin monomer were determined by electrostatic potential analysis. The interaction strength and charge transfer of gas-solid bimolecular model were calculated. The results showed that the adsorption energy of $\mathrm{C}_{4}\mathrm{~F}_{7}\mathrm{~N}/\mathrm{CO}_{2}$ mixture decomposition products and epoxy resin monomer was less than 0.06eV, the charge transfer amount is less than $0.05e$ and the adsorption process was mainly physical adsorption. The interaction strength of gas decomposition products and epoxy resin monomer was weak, and the chemical stability of gas-solid interface was good.
