Mechanism and effect of DC charge accumulation on SF/sub 6/ gas insulated spacers

Fujinami, Hideo; Takuma, Tadasu; Yashima, Masafumi; Kawamoto, Tadashi

doi:10.1109/61.32671

Cited by 104 publications

(40 citation statements)

References 8 publications

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“…This is likely due to the space charge accumulated on insulator surface and their non-uniform distribution resulting in a distortion of the electric field. The space charge can result from different processes as the interaction between the discharge and the insulator surface, and the modification of the ionisation and attachment coefficients [2,7,[17][18][19][20][21]. The presence of space charge creates a stronger field in one direction and its attenuation in the other.…”

Section: Morphology Of Creeping Dischargesmentioning

confidence: 99%

AC creeping discharges propagating over solid–gas interfaces

Sadaoui

Béroual

2014

IET Science, Measurement & Technology

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This study is aimed at the characterisation of surface discharges propagating over different solid materials namely glass, bakelite and epoxy resin immersed in three gases and their mixtures (namely SF 6 , N 2 and CO 2 , SF 6 /N 2 and SF 6 /CO 2 ) under AC voltage (50 Hz) in a point-plane electrode system. It is shown that the stopping length of discharges (L f ) increases linearly with the applied voltage and decreases when the gas pressure is increased. L f is longer in CO 2 and N 2 than in SF 6 [L f (N 2 ) > L f (CO 2 ) > L f (SF 6 )]; and the increase of SF 6 content in the investigated mixtures leads to a significant decrease of L f . Also, for a given gas, L f is slightly longer with glass and bakelite than that with epoxy resin indicating that the higher the dielectric constant, the longer the discharge is. Thus, the density of the discharge branches and L f reduce when the thickness of insulators increases and/or their dielectric constant decreases. Such observations evidence the implication of capacitive charge effect and electric field in the development of creeping discharges.

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Section: Morphology Of Creeping Dischargesmentioning

confidence: 99%

AC creeping discharges propagating over solid–gas interfaces

Sadaoui

Béroual

2014

IET Science, Measurement & Technology

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“…The accumulated charge would distort the electric field and reduce the flashover voltage along the insulator surface [1][2][3]. The surface charge can come from the gas phase and the inside of the solid insulator, and can also be generated by the inhomogeneous surface conduction along the solid insulator [4][5][6][7][8][9][10]. However, for practical gas-insulated systems, the bulk conduction and surface conduction do not seem to be the dominant mechanisms of the charge accumulation, and the electric charge is considered to mainly come from the gas phase.…”

Section: Introductionmentioning

confidence: 99%

Modulation of surface electrical properties of epoxy resin insulator by changing fluorination temperature and time

An¹,

Yin

Liu³

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

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In order to systematically investigate the modulating role of fluorination temperature and time on surface electrical properties of the epoxy resin insulator, epoxy resin sheets were surface fluorinated in a laboratory vessel using a F 2 /N 2 mixture with 12.5% F 2 by volume at 0.1 MPa and different temperatures of 25-95 °C for different times of 5-120 min. Conductivity measurements have shown that the intrinsic surface conductivity of the epoxy resin insulator could be modulated from an even lower value to a nearly four orders of magnitude higher value than the value prior to fluorination by changing the fluorination temperature and time. Surface conductivity increased with increasing fluorination temperature at the same fluorination time, while decreased to some extent with increasing fluorination time at a given fluorination temperature. Surface potential decay measurements showed consistent results with the surface conductivity measurements. ATR-IR analyses revealed substantial changes in surface chemical composition and structure, depending on the fluorination temperature and time. SEM images clearly showed an increase of the fluorinated layer thickness with increasing fluorination temperature and time. Surface cracks appeared only at elevated fluorination temperatures and increased with fluorination temperature, while the surface became compact with the duration of the fluorination. These results, compared with the previous results on an epoxy resin insulator made of DGEBA epoxy resin with a lower epoxy value, also indicated a significant influence of the epoxy resin insulator itself or the epoxy resin raw material on surface electrical properties and surface physicochemical characteristics after fluorination.Index Terms -Epoxy resin insulator, surface fluorination, fluorination temperature and time, surface electrical properties, surface charge accumulation.

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“…In addition, several mechanisms have been advanced to explain the mechanisms implicated in their initiation and development. Among these mechanisms the dynamic interaction between the discharge and the insulator surface [5 -7], the accumulation of electrical charge at the insulator surface [8][9][10][11][12][13][14], the modification of the ionisation and attachment coefficient [15,16] and the distortion of electric field [17,18]. Therefore the understanding of the initiation conditions of creeping discharges and the parameters characterising their development up to breakdown or flashover is very helpful for the design and the dimensioning of high-voltage components and systems (bushings, insulators, switchgears, gas insulating lines, gas circuit breaker .…”

Section: Introductionmentioning

confidence: 99%

Effect of micro-fillers in polytetrafluoroethylene insulators on the characteristics of surface discharges in presence of SF6, CO2 and SF6-CO2 mixture

Béroual

Coulibaly

Aitken

et al. 2012

IET Gener. Transm. Distrib.

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This study is devoted to the optical and electrical characterisation of discharges propagating over insulators made of polytetrafluoroethylene (PTFE) filled with different kinds of micro-mineral fillers immersed in gas or gaseous mixture, under lightning impulse voltage (1.2/50 ms), using a point-plane electrode arrangement. The fillers the authors investigated are MoS 2 , Al 2 CoO 4 , SiO 2 and CaF 2 . The gases and mixture the authors considered are SF 6 , CO 2 and SF 6 -CO 2 . It is shown that the stopping length of discharges L f increases quasi-linearly with the voltage; L f is shorter in SF 6 than in CO 2 and it is higher when the point electrode is positive than when it is negative while the initiation voltage of discharges is higher with a negative point than with a positive one. The discharges do not always present a radial structure as reported in the literature. Also, the type of filler greatly influences the characteristics of creeping discharges. In a given gas or mixture, the shortest L f is obtained with PTFE filled with MoS 2 or Al 2 CoO 4 . Thus, insulators with these fillers appear as the best insulators.

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Mechanism and effect of DC charge accumulation on SF/sub 6/ gas insulated spacers

Cited by 104 publications

References 8 publications

AC creeping discharges propagating over solid–gas interfaces

AC creeping discharges propagating over solid–gas interfaces

Modulation of surface electrical properties of epoxy resin insulator by changing fluorination temperature and time

Effect of micro-fillers in polytetrafluoroethylene insulators on the characteristics of surface discharges in presence of SF6, CO2 and SF6-CO2 mixture

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