Surface Flashover Test Research Articles

3D Printed Polymer Vacuum Insulator

In this paper, through the application of 3D printing technology, insulators with different surface microstructures are prepared. Surface flashover test of the printed insulators shows that surface microstructures have a strong influence on the surface flashover voltage. This indicates that through proper surface microstructure design and the application of 3D printing technology insulators with high surface voltage withstand strength can be prepared. The influence of gas release characteristics, with and without thermal treatment, on the surface flashover voltages is studied. The results indicate that insulators with lower gas release rate own higher voltage withstand strength.

Improving the surface insulating performance of epoxy resin/Al 2 O 3 composite materials by extending chain of liquid epoxy resin with Me‐THPA

Basin-type insulators are made by epoxy resin composite materials. Curing defects are easily formed in basin-type insulators, and degrade their insulating performances. High curing exothermic rates of epoxy resin composite materials have deemed as the main cause of curing defects formation. In this study, methyl tetrahydrophthalic anhydride (Me-THPA) was used to extend the molecular chain of liquid epoxy resin to prepare epoxy resin composite materials with low curing exothermic rates. Curing exothermic properties, molecular weight distribution, curing stress, microstructures, and surface flashover characteristics of the composite materials were investigated. The results showed that chain-extended epoxy resin had low curing exothermic rates. The curing stress of the chain-extended epoxy resin composite materials was small. The curing defects forming in the composite materials were inhibited. Negative DC surface flashover characteristics of these composite materials were improved. Furthermore, variation of functional groups of the composite materials was studied before and after surface flashover tests. Results showed that the content of carbon–oxygen single bonds (–C–O) in the chain-extended epoxy resin composite materials was observed to decrease. The –C–O bonds also affect the voltage withstand capability of the epoxy resin composite materials.

Vacuum surface flashover characteristics of an alumina insulator with a metalized layer

Alumina ceramics are often used as vacuum electrical device insulators owing to their excellent properties, high hardness quality, high heat resistivity, and high insulation and low gas desorption properties. As alumina is chemically stable, directly brazing it with a metal is difficult. Thus, an alumina surface is metalized using the Mo-Mn method and subsequently brazed to a metal. When a high negative voltage is applied to the alumina surface, the edge of the metalized region becomes a cathode triple junction. In this case, surface flashover can occur, which limits the equipment's surface-flashover withstand voltage. Understanding the vacuum surface-flashover characteristics that depend on the edge condition of a metalized layer is important. Herein, surface-flashover tests in vacuum were conducted using column alumina samples under different metalized-edge conditions. The results showed that the withstand voltage and conditioning speed obviously changed with the edge condition of the metalized layer.

Enhancing electrical strength of acrylate polymer by using fluorinated monomer as surface modifier

A novel method using ultraviolet (UV) cured fluoralkene to realize surface fluorination of acrylate polymer is proposed to enhance its insulation performance. Doping small amount of dofluoroheptyl methacrylate C11H8F12O2 (DFHMA) in UV acrylate resin formulation as modifier can assemble a fluorinated monomolecular layer on the surface whenas bringing little change to its morphology. The influences of the modifier on molecular structure, surface free energy, elemental composition and electric properties of acrylate polymer are investigated by attenuated total reflection infrared (ATR-IR), water contact angle, X-ray photoelectron spectroscopy (XPS), and electrical performance characterizations, respectively. Experimental results indicate that DFHMA is segregated to the surface of acrylate polymer, leading to an increase of its surface hydrophobicity. Surface flashover tests reveal that fluorinated samples have a higher degradation or tracking resistance in comparison with virgin samples. In addition, strong CF bonds also can enhance bulk breakdown characteristics by increasing charge injection barrier.

Surface Flashover Characteristics of PPLP According to Its Orientation in Cryogenic Environment

Polypropylene laminated paper (PPLP), which is used as the main insulation material of the stop joint box (SJB), has excellent dielectric characteristics in cryogenic environment. Despite excellent dielectric characteristics of PPLP, the interface between liquid nitrogen (LN2) and PPLP of the SJB is very vulnerable to the surface flashover. Therefore, it is necessary to investigate the surface flashover characteristics of dielectric materials including LN2 and PPLP for the insulation design of the SJB. PPLP has two orientations according to the direction of fiber in Kraft paper that are cross direction (CD) and machine direction (MD). The research on the mechanical properties of PPLP has been reported since there are differences in physical properties depending on its orientation. However, the study of the surface flashover characteristics of PPLP in the cryogenic environment according to its orientation has not been reported yet. Thus, the surface flashover characteristics of PPLP according to its orientations should be examined to ensure the reliability of the SJB connecting the High-temperature superconducting (HTS) dc cable. In this paper, the surface flashover characteristics of the PPLP in cryogenic environment in accordance with its orientation was fully investigated. The dc surface flashover tests were performed with different orientations of PPLP and various gap distances. In addition, the surface leakage currents were measured by increasing voltage at fixed gap distance. From the test results, the dc surface flashover voltage of CD was found to be 15-20% higher than that of MD. In addition, the breaking point of CD was three times higher than MD, and beyond the breaking point, the surface leakage current of CD was lower than that of MD. Consequently, the surface flashover characteristics of PPLP are significantly affected by fiber orientations of PPLP.

Application of Functionally Graded Materials for Solid Insulator: Fabrication, Optimization Design, and Surface Flashover of Prototype Samples

The applicability of functionally graded materials (FGM) for solid insulator of gas insulated switchgear (GIS) was investigated. First, a new fabrication method based on layer-by-layer casting technique was demonstrated to prepare FGM insulator possessing spatial distribution of dielectric constants. Then, electric field strength in the FGM spacer model was calculated and optimized by using finite element method (FEM). Three types of truncated cone spacers were fabricated according to the optimization results. Finally, surface flashover tests were performed under AC voltage and lightning impulse voltage applications. Results in both circumstances indicated an evident improvement of flashover voltage when FGM insulator was employed. As a result, we verified the fabrication technique and the applicability of FGM insulator for enhancement of insulation performance in GIS device.

An Investigation on Surface Flashover Characteristics of FRP in Several Insulation Gases for the Spacer of Cryogenic Bushing

Abstract —Superconducting equipment has been actively investigated for securing the environment and energy technology (ET) in various parts of the world. Despite these movements, a high voltage cryogenic bushing, which plays an important role of interconnection between the electric power systems and superconducting devices, has not been fully developed due to severe insulation requirements. gas A insulated cryogenic bushing has been investigated as one of our projects since 2010. a basic step to obtain the design As parameters for cryogenic bushing, we focused on the surface flashover characteristics of glass fiber reinforced plastic (FRP) in several insulation gases. the danger of reduction of the dielectric performanceFor the surface flashover tests, several insulation gases including SF6, CF 4 and N 2 gas were prepared. Various length of FRP specimens were fabricated in order to obtain the data for fundamentalcreepage distance of FRP. The first specimen group was from 2 mm to 10 mm with 2 mm intervals and the second specimen group was from 20 mm to 100 mm with 20 mm intervals. And the gas pressure was varied from 1 bar to 4 bar. n AC Aovervoltage test and a lightning impulse test were performed. Then the experimental results of surface flashover were obtained and analyzedBased on these results, it would be . possible to design the optimum creepagedistance of FRP in a cryogenic bushing.

A study on designing the electrical insulation of condenser-type terminations for 154 kV class HTS cables

To develop a high-temperature superconducting (HTS) power cable system, terminations able to be used in cryogenic temperature are absolutely necessary. The termination for HTS cable should provide electrical insulation for the conductor and not be transformed. In this research, the basic insulation design of the condenser-type termination using glass fiber reinforced plastic (GFRP), whose contraction is rare in cryogenic temperatures and mechanical characteristic is excellent, was carried out. LN 2-end clearance, the bottom of the termination, was designed through a surface flashover test of GFRP in LN 2 while the interval of the condenser and the diameter of termination were designed through a puncture breakdown test of mini models with electrode structures same as termination.