Approche physique du développement de streamers positifs sur une surface de glace =

Ndiaye, Ibrahima

doi:10.1522/030008653

Cited by 6 publications

(6 citation statements)

References 69 publications

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“…When the white arc reaches its critical length [20], flashover occurs along the whole insulator [ 23]. In order to study the mechanism of arc propagation over an ice surface [24,25] and estimate the critical flashover voltage [26,27] different static and dynamic models were originally established under AC and DC voltages [20,[28][29][30][31]. Contrary to static models, which calculate the flashover voltage of ice-covered insulators, dynamic models can contribute to a better understanding of the discharge mechanisms involved in the time-dependent evolution of the flashover's main parameters.…”

Section: Introductionmentioning

confidence: 99%

Dynamic modeling of AC multiple ARCS of EHV post station insulators covered with ice

Taheri

Farzaneh

Fofana

2015

IEEE Trans. Dielect. Electr. Insul.

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The present contribution proposes a multi-arc dynamic model to predict the parameters of AC flashover propagating over EHV ice-cover insulators. The model considers the arc as time-dependent impedance consting of a resistance in series with an inductance. The residual ice layer is specified in terms of an equivalent resistance, where the equivalent surface conductivity is calculated by taking into account the water film flowing over the glass surface. The temporary arc length developing over an icecovered insulator is calculated through the arc velocity, determined using high-speed image recording techniques. The principal characteristics of flashover, including minimum flashover voltage, leakage current and arc velocity are investigated through the proposed multi-arc dynamic model. The proposed models were successfully validated in the laboratory using station post insulators -typically used in Hydro- Quebec 735 kV substations -under AC voltage based on the standard method presented in IEEE Std 1783. Good agreement was also observed between the flashover voltage calculated from the proposed multi-arc model and those obtained experimentally on ice-covered EHV insulators. The proposed model is helpful for properly designing and selecting the EHV insulators used in cold climate conditions.Index Terms -Multi-arc model, ice-covered insulator, maximum withstand voltage, air gap, flashover, electric arc.

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Section: Introductionmentioning

confidence: 99%

Dynamic modeling of AC multiple ARCS of EHV post station insulators covered with ice

Taheri

Farzaneh

Fofana

2015

IEEE Trans. Dielect. Electr. Insul.

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“…In 1970, they also proposed the creation of the ‘ASCC’ ( Association sportive, culturelle et cooperative ) and the ‘ASCA’ ( Association sportive, culturelle et artisanale ) 12 . According to several authors, ONCAV asked navétanes teams to restructure as ASCs and to choose new (Wolof) names (Ndiaye 1982: 26; Niang 1994–5: 35). Former members of the teams, however, explained in interviews that the ‘ASC’ idea was theirs.…”

Section: Control and Contest: The Navétanes Teams 1970s To 1980smentioning

confidence: 99%

“…Clubs also organized dance parties for which they sold tickets. Club leaders were ready to ‘sacrifice everything’ for the success of their team (Ndiaye 1982: 27–8). Supporters were motivated simply by ‘affection for the neighbourhood’, a former club member remembered 14 .…”

Section: Control and Contest: The Navétanes Teams 1970s To 1980smentioning

confidence: 99%

URBAN FOOTBALL PERFORMANCES: PLAYING FOR THE NEIGHBOURHOOD IN SENEGAL, 1950s–2000s

Baller¹

2014

Africa

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In Senegal, neighbourhood football teams are more popular than teams in the national football league. The so-called navétanes teams were first created in the 1950s. Since the early 1970s, they have competed in local, regional and national neighbourhood championships. This article considers the history of these clubs and their championships by focusing on the city of Dakar and its fast-growing suburbs, Pikine and Guédiawaye. Research on the navétanes allows an exploration of the social and cultural history of the neighbourhoods from the actor-centred perspective of urban youth. The history of the navétanes reflects the complex interrelations between young people, the city and the state. The performative act of football – on and beyond the pitch, by players, fans and organizers – constitutes the neighbourhood as a social space in a context where the state fails to provide sufficient infrastructure and is often contested. The navétanes clubs and championships demonstrate how young people have experienced and imagined their neighbourhoods in different local-level ways, while at the same time interconnecting them with other social spaces, such as the ‘city’, the ‘nation’ and ‘the world’.

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“…In order to study the mechanism of arc propagation over an ice surface [27], [28] and estimate the critical flashover voltage [18], [22], [29], [30], different static and dynamic models were originally established under AC and DC voltages [26], [31], [32], [33]. Contrary to static models which calculate the critical flashover voltage of ice-covered insulators, dynamic models can contribute to a better understanding of the discharge mechanisms involved in the time dependent evolution of the main parameters of the flashover.…”

Section: Equipment (Cigele) and Canada Research Chair On Engineering mentioning

confidence: 99%

Two-arc dynamic modeling of AC and DC flashovers of EHV post station insulators covered with ice based on laboratory experiments /

Ledari¹

2014

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Ice and snow accretion on insulators has been recognized as a significant risk factor in the reliability of overhead transmission lines and substations. Accumulated ice on insulators can initiate corona discharge along ice-free zones, often called air gaps. In the presence of a highly conductive water film on the surface of the ice, while applied voltage is sufficiently high, corona discharge activity may be initiated and developed into partial arcs. Under certain conditions, these partial arcs may result in complete flashover.The general objective of this research is to study the flashover phenomenon on icecovered extra-high-voltage (EHV) post insulators. Hence, a two-arc dynamic model based on the existing mathematical models was proposed to predict the parameters of AC and DC flashovers. The model considers the arc as time-dependent impedance constituted of a resistance in series with an inductance. The residual ice layer is defined in terms of an equivalent resistance, where the equivalent surface conductivity is calculated by taking into account the water film flowing along the ice surface. The present contribution proposes a novel approach to determine the equivalent surface conductivity, based on fluid mechanics and the Navier-Stokes equations, as well as on a series of experiments carried out to measure the water film flow rate and conductivity.Moreover, the mechanisms of discharge initiation and arc development on the surface of the ice accumulated on the insulators were studied. Special attention was paid to evaluate the effect of the volume conductivity of the ice surface on the arc propagation velocity for different freezing water conductivities, using high-speed video camera techniques.The proposed models were successfully validated in laboratory using station post insulators -typically used in Hydro-Quebec 735 kV substations -under AC and DC voltages. The maximum AC and DC withstand voltages were experimentally determined based on IEEE Std 1783. Furthermore, the influence of the number and position of air gaps on the flashover performance of ice-covered insulators was investigated experimentally. Experimental results revealed that the air gap configuration affects the maximum withstand voltage significantly. The main characteristics of flashover, including minimum flashover voltage and leakage current, derived from the proposed two-arc dynamic model, respond properly to the variation of major parameters, namely, insulator length and freezing water conductivity.Finally, in order to interpret the performance of insulators under different air gap positions, the voltage and electric field distributions along the ice-covered insulator were simulated numerically during the melting period, using the Finite Element Method (FEM). Simulations results confirm that increasing the number of air gaps improves the maximum withstand voltage and uniformity of voltage distribution of EHV post insulators. Based on the results, the use of booster sheds and grading rings to improve the insulating performance of...

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Approche physique du développement de streamers positifs sur une surface de glace =

Cited by 6 publications

References 69 publications

Dynamic modeling of AC multiple ARCS of EHV post station insulators covered with ice

Dynamic modeling of AC multiple ARCS of EHV post station insulators covered with ice

URBAN FOOTBALL PERFORMANCES: PLAYING FOR THE NEIGHBOURHOOD IN SENEGAL, 1950s–2000s

Two-arc dynamic modeling of AC and DC flashovers of EHV post station insulators covered with ice based on laboratory experiments /

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