Vacuum insulator flashover mechanisms, diagnostics and design implications

Wetzer, J.M.

doi:10.1109/94.625347

Cited by 32 publications

(5 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The shape of the insulator is also important, since a conical shape with a positive angle (i.e. larger on the cathode side) has been found to yield the highest performances [22][23][24]. The insulator surface plays an important role in determining the characteristic flash-over voltage: grain boundary defects must then be minimized to optimize the performances [25].…”

Section: The Vacuum Gap Bridged By An Insulatormentioning

confidence: 99%

Adaptation of the 1 MV bushing to the SINGAP concept for the ITER NB injector test bed

Masiello¹

2006

Nucl. Fusion

View full text Add to dashboard Cite

The 1 MV bushing of the ITER NB injector is probably one of the most challenging components of the whole accelerator, since such a high voltage (HV) in a contaminated and radiated environment requires the development of non-standard technologies. This paper intends to provide a guideline for the design of 1 MV bushing for the ITER neutral beam injector test bed. Although mainly focused on the SINGAP alternative concept of the injector, the reported general criteria can be useful for the design of other HV components, such as post insulators of the acceleration grids. For every different kind of required insulation, basic physical models describing breakdown phenomena are reported together with the main technological implications and the practical recommendations necessary to improve insulation performance. The results of the finite element analyses of 1 MV bushing, operating at CEA-Cadarache laboratories, are used to validate general criteria in a typical geometry. The effects of radiation, such as neutrons and gamma rays, on solid insulators and gases have also been taken into account, describing the most important phenomena and the related implications in terms of voltage hold-off capabilities. Finally the design of the bushing in the SINGAP option and the solutions adopted are described.

show abstract

Section: The Vacuum Gap Bridged By An Insulatormentioning

confidence: 99%

Adaptation of the 1 MV bushing to the SINGAP concept for the ITER NB injector test bed

Masiello¹

2006

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…There are many factors which affect the surface flashover voltage of dielectric, such as applied voltage waveform, electrode material, surrounding insulating environment, geometry and material of the insulator, surface characteristics (including SEEY, surface roughness, surface conductivity, and surface traps), and so on [4][5][6][7]. Furthermore, surface modification methods including pre-discharge treatment, fluorination, and coating, etc., are applied to improve the surface flashover performance [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Flashover Voltage of Epoxy FRP Insulators with Different Surface Roughness and Groove under Nanosecond Pulses in SF6

et al. 2022

View full text Add to dashboard Cite

In order to further improve the insulation performance of fiber reinforce plastic (FRP) materials used in electromagnetic pulse (EMP) simulators, the flashover characteristics of FRP materials with different surface roughness and groove, i.e., those who are easily achieved and have a prominent effect, are investigated in 0.1 MPa SF6 under nanosecond pulse voltage with a rise time of 20–30 ns. The experimental results show that surfaces with different roughness have no significant influence on the flashover voltages of the FRP insulators, and both the convex grooves made of FRP and the convex grooves with nylon rings inlaid to form projections can improve the surface flashover voltage of epoxy FRP insulators under nanosecond pulse, in which the effect of the former surface is more obvious. For the insulators with convex grooves made of FRP, it is found that the root of the FRP protrusions breaks down after a number of shots with the occurrence of carbonization channels and spots, which is nonexistent for the nylon projections. Combined with the test results of surface characteristics, the surface roughness and the secondary electron emission yield (SEEY) are not key factors of flashover characteristics in SF6 under nanosecond pulse, arguably due to the fact that the energy needed for an incident electron to ionize an SF6 molecule is lower than that to excite two secondary electrons. Hence, the flashover performance cannot be improved by adjusting the surface roughness, and the flashover channel is principally governed by the macroscopic distribution of electrical field which can be changed by the convex groove. Breakdown phenomena of FRP protrusions indicate that the bulk insulation performance of resin FRP is weaker compared to pure resin because of its composite structure, as well as the impurities and voids introduced in the manufacturing process. The results are instructive for the design of FRP insulation structures in the compact EMP simulator.

show abstract

“…The electrical charging phenomena on the surface under vacuum have been studied to date [4,5,6]. It is understood that the electrical charging under vacuum occurs in the following four steps (see Figure 1):…”

Section: Introductionmentioning

confidence: 99%

Characteristics of electrical charging on smooth and rough surfaces of glass plates under vacuum

Mikami

Yokosuka

Hatanaka

2016

IEEE Trans. Dielect. Electr. Insul.

View full text Add to dashboard Cite

To investigate the electric-charging characteristics of an insulator under vacuum, a system for measuring the potential distribution on the surface of an insulator under vacuum was developed and used to measure potential distributions on smooth and rough surfaces of several glass plates. The measured potential distributions after surface discharges indicate that compared to discharges on the rough surface, the discharges on the smooth surface tend to occur at lower positive potential. On the other hand, during micro discharge caused by partial discharge of the electrode, in the potential distributions of both the smooth and rough surfaces, a negative peak near the negative HV electrode and a positive peak near the GND electrode were observed. Moreover, the positive electric field on the rough surface is lower than that on the smooth surface during micro discharge. These potential distributions are supposed to be caused by scattering and attachment of electrons drifting on the surface. Sandblasting was applied for roughening the insulators, and it is considered to be suitable for mass production of the vacuum-insulated DC high-voltage systems because it is low cost and easy to perform.Index Terms -Discharge, surface charging, micro discharge, breakdown under vacuum, surface roughness, glass.

show abstract

Vacuum insulator flashover mechanisms, diagnostics and design implications

Abstract: Link to publication

Cited by 32 publications

References 26 publications

Adaptation of the 1 MV bushing to the SINGAP concept for the ITER NB injector test bed

Adaptation of the 1 MV bushing to the SINGAP concept for the ITER NB injector test bed

Flashover Voltage of Epoxy FRP Insulators with Different Surface Roughness and Groove under Nanosecond Pulses in SF6

Characteristics of electrical charging on smooth and rough surfaces of glass plates under vacuum

Contact Info

Product

Resources

About