The Cold Fog Test

Chisholm, William A.; Ringler, K. G.; Erven, C.C.; Green, M. A.; Melo, O.T.; Tam, Y. T.; Nigol, O.; Kuffel, J.; Boyer, Alexandre; Pavasars, I.K.; Macedo, F. X.; Sabiston, J.K.; Caputo, R.B.

doi:10.1109/mper.1996.4311032

Cited by 47 publications

(32 citation statements)

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“…Chisholm et al [80] presented a cold-fog test method to reproduce a flashover on an insulator while considering surface contamination, ice and fog by rising temperature to 0 °C. The electrical performance of outdoor insulators, designed for a 115 kV, 230 kV and 500 kV substations, degrades severely under these conditions.…”

Section: Effect Of Applied Water Conductivitymentioning

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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Section: Effect Of Applied Water Conductivitymentioning

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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“…The maximum velocities reach about 100 m/s and 50 m/s for outer and inner arcs respectively, just before flashover [28]. The radius of both inner and outer arc is proportional to the square root of the leakage currents as given by equations (3-12) through (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Under AC conditions and for rectangular ice samples, the partial arc on ice surfaces extinguishes and reignites with the cyclical variation of the applied…”

Section: Arc Constants and Re-ignition Parameters On Ice Covered Surfacementioning

confidence: 99%

“…By recalling equations (3-4) through (3-6) and (3-12) through (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), the values for f e and r 0 can be substituted with respect to the applied freezing water conductivity and the leakage current, respectively. In order to calculate the critical current I c9 arc length x c and flashover voltage v c , the same analysis was made as that of Alston and Zoeledzioski [3] (Section 2.4.1.3), where the value of v c for a given arc length x can be obtained from equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) by equating the first derivative of voltage V with respect to I to zero:…”

Section: Arc Constants and Re-ignition Parameters On Ice Covered Surfacementioning

confidence: 99%

“…In order to calculate the critical current I c9 arc length x c and flashover voltage v c , the same analysis was made as that of Alston and Zoeledzioski [3] (Section 2.4.1.3), where the value of v c for a given arc length x can be obtained from equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) by equating the first derivative of voltage V with respect to I to zero:…”

Section: Arc Constants and Re-ignition Parameters On Ice Covered Surfacementioning

confidence: 99%

“…The critical arc length is also obtained from equation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) as:…”

Section: Arc Constants and Re-ignition Parameters On Ice Covered Surfacementioning

confidence: 99%

See 2 more Smart Citations

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

Sabri¹

2009

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Experimental study and mathematical modelling of flashover on extra‐high voltage insulators covered with ice

Farzaneh-Dehkordi

Zhang

Farzaneh

2004

Hydrological Processes

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Abstract:Using a test method developed at the high-voltage laboratory of the NSERC/Hydro-Quebec/UQAC Industrial Chair on Atmospheric Icing of Power Network Equipment (CIGELE), the relation between the minimum flashover voltage V MF and the insulator dry arcing distance for standard porcelain station post insulators, as typically used in Hydro-Quebec substations, was investigated under icing conditions. The experimental results show that, under wet-grown ice, known as the most dangerous type of ice for power transmission systems, the V MF increases nonlinearly with an increase in insulator length. Based on these results, an improved mathematical model for predicting the critical flashover voltage versus length of ice-covered insulators is presented. This model is helpful for understanding the flashover phenomenon on ice-covered insulators and presents a powerful tool for choosing the proper length of outdoor insulators in cold climate regions.

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The Cold Fog Test

Cited by 47 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 =

Experimental study and mathematical modelling of flashover on extra‐high voltage insulators covered with ice

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