A new approach for assessing the moisture content in SF&lt;inf&gt;6&lt;/inf&gt;-insulated equipment

Lessard, M-C; Larocque, Germain; Gendron, Stéphane; Laberge, S.; Lavoie, Y.

doi:10.1109/eic.2016.7548659

Cited by 3 publications

(5 citation statements)

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“…The focus was set on the range of humidity applicable to operating gas-insulated devices, which investigated its influence on the spatially resolved charge accumulation over time. In accordance with the literature, the humidity of the devices equipped with molecular sieves could range up to 800 ppm v [13], which approximately corresponds for a gas pressure of 0.45 MPa and temperature of 20°C to the IEC limit for gas-insulated HV equipment of −5°C frost-point [14].…”

Section: Resultssupporting

confidence: 77%

“…Long-term humidity measurements, with gas-insulated devices on-site, showed humidity levels ranging up to 800 ppm v in summer when placing molecular sieves in the gas compartment. In the highly unlikely scenario that a desiccant was missing, the humidity of up to 2000 ppm v was measured [13]. Generally, the humidity was found to be a system parameter for which absorption and emission from interfaces must be considered.…”

Section: Introductionmentioning

confidence: 99%

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Influence of humidity on conduction processes in gas‐insulated devices

2020

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Humidity has been considered as one of the main influencing factors that determine the conduction processes and electric strength of gas-insulated systems. Whereas in the past, various studies focused on the change in the partial discharge inception voltages, breakdown strength of homogeneous and inhomogeneous field arrangements, and insulator flashover voltage, recent studies have investigated the changes in ion currents measured through different gas gaps. In the framework of this contribution, a highly precise humidity control circuit has been developed to analyse the significance of humidity in the range from −25 to −5°C frost-point, which is fully applicable to operating gas-insulated devices. Using sulphur hexafluoride (SF 6 ) as the insulation gas at 0.45 MPa, Al 2 O 3 -filled epoxy resin insulators, and technically rough electrodes, the humidity was found to significantly influence the intensity of microdischarges at interfaces. Charge generation from microdischarges at the interfaces substantially increased with increasing humidity. For an electric field of 5 kV/mm that were applicable to the dimensioning of gas-insulated devices, humidity strongly influences the charge provision from technically rough interfaces and potentially contributes to the surface-charge accumulation at insulator surfaces. On the other hand, for low-field conduction phenomena, no increase in the ion currents from natural ionisation or electrophoretic conduction was observed. For the investigated range of parameters, humidity is expected to be highly relevant for the design of gas-insulated devices.

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Section: Resultssupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Influence of humidity on conduction processes in gas‐insulated devices

2020

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“…However, surface conductivity may play a minor role in surface charging and charge decay in gas-insulated HVDC equipment under operation. Some publications have indicated that, for untreated epoxy spacers under dry conditions, the charge transport along the interface can be neglected [10,20]. This suggestion is confirmed by the discharging sequences shown in Section 5, which do not show changes in flank slopes or location, despite significant tangential field stress.…”

Section: Discussionmentioning

confidence: 53%

“…The non-linear surface conductivity of the insulator surfaces has been characterized by some authors as the main parameter determining the surface charge accumulation of untreated small-scale GIS-spacers [17,18]. The results of other studies indicate that a distinct surface property can be measured only under high levels of humidity [10,20]. This property's influence on surface conductivity was characterized to be particularly significant at humidity levels greater than 20% RH at 40°C and atmospheric pressure.…”

Section: Conduction Through Solid Insulation and Along Insulator Surfmentioning

confidence: 99%

“…This property's influence on surface conductivity was characterized to be particularly significant at humidity levels greater than 20% RH at 40°C and atmospheric pressure. This environment is unlikely to be exhibited in equipment under operation [10,20]. Sandblasting the insulator surface to change the interface's roughness has also been suggested to strongly influence the surface conductivity and its dependency on humidity [11].…”

Section: Conduction Through Solid Insulation and Along Insulator Surfmentioning

confidence: 99%

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Conduction processes in gas-insulated HVDC equipment: from saturated ion currents to micro-discharges

Tschentscher

Franck

2018

IEEE Trans. Dielect. Electr. Insul.

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Charge generation in gas-insulated high-voltage direct current (HVDC) equipment has been investigated since surface charge accumulation was detected as the main challenge to insulation coordination. Over the years, researchers have made enormous progress using continuous ion current measurements or surface charging experiments with model spacers downscaled from gas-insulated components. Whereas the low sensitivity of the former method limits its measurement range, the latter method is timeconsuming and demands comprehensive modeling. In this paper, more than 3,000 hours of surface charge measurements are presented, covering the full range of charge generation processes from ion currents owing to natural ionization to the inception of micro-discharges. In accordance with gas-insulated equipment, Al2O3filled epoxy resin was used for the solids, and sulfur hexafluoride (SF6) was used for the gaseous insulation. It has been demonstrated that the ion pair generation from natural ionization in the gas is significantly influenced by the surrounding solid materials, and therefore, scales with the insulation volume. From the onset of micro-discharges, sharp and locally limited charge patterns are formed, as surface conductivity does not appear to influence the investigated charge distributions. Whereas the primary charge dissipation from surface areas centered at the distribution could be explained in terms of the gas volume size, the discharge currents could not be reproduced with common ion-current models. At low electric fields, the observed charge decay indicates the presence of low-field conduction processes that cannot be explained by charge generation from natural ionization in the gas.

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