Nonlinear resistive electric field grading Part 2: Materials and applications

Donzel, L.; Greuter, F.; Christen, Thomas

doi:10.1109/mei.2011.5739419

Cited by 260 publications

(120 citation statements)

References 15 publications

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“…8,9 Some advocate semi-conductive coatings, 10 while others do not see any advantage in doing so, because paradoxically, surface charge accumulation increases instead and problems at the triple-junction point and insulation middle part appear. 1,7 Recently, surface modification by dielectric barrier discharge using Ar and CF 4 as working gas was reported to enhance surface flashover strength of polymethylmethacrylate.…”

Section: Introductionmentioning

confidence: 99%

Suppression of surface charge accumulation on Al2O3-filled epoxy resin insulator under dc voltage by direct fluorination

Zhang

Wang

et al. 2015

AIP Advances

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Surface charge accumulation on insulators under high dc voltage is a major factor that may lead to the reduction of insulation levels in gas insulated devices. In this paper, disc insulators made of Al2O3-filled epoxy resin were surface fluorinated using a F2/N2 mixture (12.5% F2) at 50 °C and 0.1 MPa for different durations of 15 min, 30 min and 60 min. A dc voltage was applied to the insulator for 30 min and the charge density on its surface was measured by an electrostatic probe. The results revealed significant lower surface charge densities on the fluorinated insulators in comparison with the original one. Surface conductivity measurements indicated a higher surface conductivity by over three orders of magnitude after fluorination, which would allow the charges to transfer along the surface and thus may suppress their accumulation. Further, attenuated total reflection infrared analysis and surface morphology observations of the samples revealed that the introduction of fluoride groups altered the surface physicochemical properties. These structure changes, especially the physical defects reduced the depth of charge traps in the surface layer, which was verified by the measurement of energy distributions of the electron and hole traps based on the isothermal current theory. The results in this paper demonstrate that fluorination can be a promising and effective method to suppress surface charge accumulation on epoxy insulators in gas insulated devices.

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Section: Introductionmentioning

confidence: 99%

Suppression of surface charge accumulation on Al2O3-filled epoxy resin insulator under dc voltage by direct fluorination

Zhang

Wang

et al. 2015

AIP Advances

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“…To decrease force disturbances and the cable mass, the operating voltage of the actuators is increased to above 2000 V. As a result, partial discharges occur during the expected lifetime of an inverter-fed actuator [1]. To ensure that the linear actuators reach their expected lifetime, electric field control methods have to be employed as is performed in cable accessories of medium and high-voltage networks [2][3][4][5] and high-voltage rotating machines [6][7][8]. These electric field control methods mitigate electric field stress and, therefore, ensure the partial discharge inception voltage is above the operating voltage.…”

Section: Introductionmentioning

confidence: 99%

Analysis of electric field control methods for foil coils in high-voltage linear actuators

Beek¹,

Jansen²,

Lomonova³

2015

Archives of Electrical Engineering

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This paper describes multiple electric field control methods for foil coils in high-voltage coreless linear actuators and their sensitivity to misalignment. The investigated field control methods consist of resistive, refractive, capacitive and geometrical solutions for mitigating electric stress at edges and corners of foil coils. These field control methods are evaluated using 2-D boundary element and finite element methods. A comparison is presented between the field control methods and their ability to mitigate electric stress in coreless linear actuators. Furthermore, the sensitivity to misalignment of the field control methods is investigated.

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“…A possible and still new approach is the use of microvaristors for this purpose. Microvaristors are small, sintered particles of doped ZnO having a welldefined, intrinsic non-linear conductivity (E) [1]. The non-linearity of microvaristors is expressed by the exponent of non-linearity, which ranges up to 30 [1].…”

mentioning

confidence: 99%

“…Microvaristors are small, sintered particles of doped ZnO having a welldefined, intrinsic non-linear conductivity (E) [1]. The non-linearity of microvaristors is expressed by the exponent of non-linearity, which ranges up to 30 [1]. They become increasingly conductive above a certain level of the applied electric field, the "switching field strength".…”

mentioning

confidence: 99%

“…They become increasingly conductive above a certain level of the applied electric field, the "switching field strength". One main advantage of microvaristors used as functional fillers is the fact that the conductivity is mainly determined by the internal potential barriers within the particles, rather than by effects at the boundaries between the particles, and their electrical characteristic is tuned by variation of the doping elements or the sintering parameters [1]. For d.c. applications, the filling degree must be chosen above the percolation threshold to provide conduction paths inside the polymer.…”

mentioning

confidence: 99%

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Short and long term behavior of functionally filled polymeric insulating materials for HVDC insulators in compact gas-insulated systems

Tenzer¹,

Secklehner²,

Hinrichsen³

2018

NORD-IS

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<p>Conventional insulators optimized for high-voltage alternating current transmission tend to accumulate surface and volume charges in direct voltage applications. This is especially true for gas-insulated systems, where the surrounding gas is extremely dry, thus having very low conductivity. This may result in a strong decrease of the dielectric strength of the insulators and can lead to dielectric breakdown, especially when polarity reversals are applied. Main challenges for the development of HVDC insulators are avoiding surface and volume charge accumulations and featuring both suitable capacitive and resistive field distributions. The use of polymeric insulation materials filled with functional fillers of defined low and possibly non-linear, field dependent electric conductivity avoids these charge accumulations. <br />Several specimens of polymeric insulation materials of different, controlled conductivities for high field stress applications were produced and experimentally investigated for this contribution. Since electric conductivity depends on parameters such as temperature, humidity or long term ageing, the longterm behavior of the specimens was investigated in 1000 h tests under temperature and electrical field stress. Furthermore, tests in a high-voltage gas insulated test setup were performed in order to determine the dielectric strength of the filled polymers under high electric stationary and transient fields as present in gas insulated systems. Results of these investigations are presented and discussed in detail in this contribution.</p>

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Nonlinear resistive electric field grading Part 2: Materials and applications

Cited by 260 publications

References 15 publications

Suppression of surface charge accumulation on Al2O3-filled epoxy resin insulator under dc voltage by direct fluorination

Suppression of surface charge accumulation on Al2O3-filled epoxy resin insulator under dc voltage by direct fluorination

Analysis of electric field control methods for foil coils in high-voltage linear actuators

Short and long term behavior of functionally filled polymeric insulating materials for HVDC insulators in compact gas-insulated systems

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