Flashover mechanism of polluted insulation

Hampton, B.F.

doi:10.1049/piee.1964.0155

Cited by 121 publications

(94 citation statements)

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“…Due to these dry bands, the current flow cannot cross the insulator surface, and consequently most of the applied voltage appears across these narrow dry bands. If the electric field along the dry bands exceeds its dielectric strength, an arc is initiated and may lead to flashover [15], [16], [17].…”

Section: List Of Tablesmentioning

confidence: 99%

“…Arc Residual resistance HV Neumarker [109] Hampton [15] stated that a necessary condition for arc development along the polluted layer is when the electric field in the arc becomes less than that of the pollution layer.…”

Section: 3) (24)mentioning

confidence: 99%

“…Based on Hampton's investigations -in the case of a cylindrical configuration with practically constant resistance per unit length -an arc will propagate if the voltage gradient (kV/m) along the cylinder (water column in Hampton tests), E ice , is higher than the voltage gradient in the arc column E arc [15]:…”

Section: Propagation Criterion and Arc Velocitymentioning

confidence: 99%

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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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Section: List Of Tablesmentioning

confidence: 99%

Section: 3) (24)mentioning

confidence: 99%

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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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“…Therefore» in order to initiate an arc on a polluted insulator surface, the voltage distribution should be highly non uniform. Generally, the formation of a dry band on a polluted insulator surface takes place in the following steps: [49] A polluted surface subjected to wetting condition is initially dry and the voltage distribution is linear as long as the resistance per length of the conductive layer is uniform.…”

Section: 3mentioning

confidence: 99%

Static modelling of AC flashover on contaminated insulators covered with ice using intelligent identificat ion methods =

Sabri¹

2009

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“…These constants may vary in accordance with the arc medium material and ambient conditions. A survey of the literature shows that the values of A and n, as measured or utilized by different investigators, vary over a wide range for different types of arc (see Table 2.3) [3,21,23,38,40,41,50,51,52,53]. These values depend not only on the arc medium but also on the electrolyte used to form the resistive layer.…”

Section: -5 Modeling Of Flashovermentioning

confidence: 99%

Modeling of AC arc inside wet snow =

Hemmatjou¹

2006

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Flashover mechanism of polluted insulation

Cited by 121 publications

References 0 publications

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

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

Static modelling of AC flashover on contaminated insulators covered with ice using intelligent identificat ion methods =

Modeling of AC arc inside wet snow =

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