Influence of Humidity on Lightning and Switching Impulse Flashover Voltages

Harada, Tatsuya; Aihara, Yoshinori; Aoshima, Yoshihide

doi:10.1109/tpas.1971.293127

Cited by 30 publications

(2 citation statements)

References 2 publications

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“…The corresponding average increase in inception voltage was about 3.32 %. This increase is in the order of 1 % for a 1 g/m 3 increment of water content in air [74]. Thus, it can be concluded that in this region the first effect, decreased ionization activity in the presence of water molecules, is dominant.…”

Section: Effect Of Humiditymentioning

confidence: 87%

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Mechanisms of arc propagation over an ice surface /

Farokhi¹

2010

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Outdoor insulation design with regard to pollution and icing performance is a critical factor for reliability of overhead transmission lines. The majority of failures occurring on transmission lines are caused by environmental conditions such as lightning, pollution and/or ice. Accumulated ice on insulators may initiate corona discharge; these partial arcs sometimes lead to flashover. This phenomenon is mainly caused by the presence of a highly conductive water film on the surface of the ice and ice-free zones, often called air gaps, along the insulators, and decreased insulator leakage distance caused by ice bridging.The general objective of this research is to investigate the physical mechanisms involved in the propagation of electric arc on the surface of ice. In the present research work, high-speed photography techniques was combined with synchronized electrical measurements to study the various parameters of arc on an ice surface, such as channel radius and propagation velocities. These results, together with studying the propagation patterns and arc foot geometries, provide background information for understanding the complete flashover phenomenon. Arc root structure, current profile, propagation pattern and velocity were investigated under positive and negative polarities. Water film conductivity and thickness, and relative air humidity were also analyzed as influencing parameters of arc propagation. The effects of different mechanisms, e.g. collision and thermal ionization, buoyancy force and electrostatic force, on different stages of arc propagation are also discussed.Repetitive patterns corresponding to arc decays were observed during arc propagation. During arc re-ignitions, an anode-directed streamer was found to be dominant, regardless of the polarity of applied voltage. The arc root under de-positive applied voltage was branched; on the contrary, the negative arc root appeared as a diffused luminous region. In the arc channel section, two distinct regions were distinguished. A linear relationship between the initiation current and the inverse of residual resistance was established, showing how important is the effect of water film thickness on the initiation of discharge. It was found there is a direct relationship between the slope of current increase and the applied water conductivity. Air humidity increases the voltage gradient along the arc channel and reduces the discharge activities at the arc tip. However, it could influence the arc formation and its propagation by changing the thickness of the water film. A change in the dominant mechanism from thermal ionization to collision ionization in the enhanced electric field was found to be responsible for the flashover. Tare. L'effet de différents mécanismes comme les collisions et l'ionisation thermique, la force de flottabilité et la force électrostatique sur les différentes étapes de la propagation de l'arc ont également été discutés. 11 RESUME

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Section: Effect Of Humiditymentioning

confidence: 87%

“…1 % / (g/m 3 ) over a wide range of humidity [74]. Kuffel [75] first noted that the enhanced electrical behavior of air by water vapor is comparable to electro-negative gases, and is qualitatively due to the loss of free electrons by attachment and absorption of photons by water vapor.…”

Section: 5» the Effect Of Humiditymentioning

confidence: 99%

Mechanisms of arc propagation over an ice surface /

Farokhi¹

2010

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Insulator Electrical Performance in Pollution Conditions

Farzaneh

Chisholm

2009

Insulators for Icing and Polluted Environments

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Assessment of air‐density correction for practical electrode systems

Boutlendj

Allen

1996

Int Trans Elec Energy Syst

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A survey is given of available data on the effects of air density upon pre-discharges and sparkover f o r nonuniform Feld geometries under a variety of voltage waveshapes of both polarities. Semi-empirical relationships describing the trends of the experimental data are presented The correction methods set up by the IEC are reviewed and some emphasis has been given to the need to distinguish between the separate influences of pressure and temperature in the overall air-density Correction factors. The limits of applicability f o r density correction are also discussed. Finally. a generalised semi-empirical equation raking into account the main atmospheric variations is proposed. This is shown to offer a good accuracyfor the calculation of sparkover voltages over a wider densitv range thon has been hitherto been possible.

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Influence of Humidity on Lightning and Switching Impulse Flashover Voltages

Cited by 30 publications

References 2 publications

Mechanisms of arc propagation over an ice surface /

Mechanisms of arc propagation over an ice surface /

Insulator Electrical Performance in Pollution Conditions

Assessment of air‐density correction for practical electrode systems

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