Experimental study and analysis of corona discharge parameters on an ice surface

Farzaneh, M.; Fofana, I.

doi:10.1088/0022-3727/37/5/012

Cited by 43 publications

(49 citation statements)

References 25 publications

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“…In general, flashover occurs faster for higher conductivities than for lower ones. Indeed, an increased ice surface conductivity leads to a much faster streamer development [14]. …”

Section: Flashover Resultsmentioning

confidence: 99%

“…The conductivity of the ice surface can reach values as high as ten times those of freezing water conductivity, σ [15]. This increase in surface conductivity caused by the rejection of impurities from the solid part into the liquid portion of drops or droplets during the solidification/freezing process, and by pollution of the water and ice surface [14,15], means that voltage drops occur essentially across the air gaps [16]. If the electric field across air gaps is high enough, corona discharges are initiated.…”

Section: Effects Of Initial Air Gap Lengthmentioning

confidence: 99%

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Dynamics and modeling of AC arc on surface of ice

Tavakoli¹,

Farzaneh²,

Fofana³

et al. 2006

IEEE Trans. Dielect. Electr. Insul.

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A self-consistent dynamic model allowing the prediction of ac discharge activities leading to flashover on ice-covered insulator surface is presented. This model takes into account the effects of a number of parameters including insulator geometry and applied water conductivity. The instantaneous variations of major parameters are discussed in order to develop a sequential time-dependent simulation of the flashover. The temporal evolution of arc current and axial arc velocity are determined in a consistent manner. The critical flashover voltage characteristics, as a function of surface conductivity, insulator length, and insulator diameter, calculated by the model are quite satisfactory when compared to the experimental results from empirical models reported in the literature.

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“…In general, flashover occurs faster for higher conductivities than for lower ones. Indeed, an increased ice surface conductivity leads to a much faster streamer development [14]. …”

Section: Flashover Resultsmentioning

confidence: 99%

Section: Effects Of Initial Air Gap Lengthmentioning

confidence: 99%

Dynamics and modeling of AC arc on surface of ice

Tavakoli¹,

Farzaneh²,

Fofana³

et al. 2006

IEEE Trans. Dielect. Electr. Insul.

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“…Hence, the flashover process can generally be summarized as follows [19], [22], [23], [24]. Following ice accretion, several sections of the insulators, especially the areas near the electrodes, may become free of ice mainly due to sunshine or the heating effect of partial discharges as well as nonuniform distribution of applied voltage along the insulator.…”

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

confidence: 99%

“…Researchers do agree that ice surface flashover resulting from an interaction involving service voltage, wet and polluted ice surface, presence of air gaps at the ice surface, environmental conditions, and the geometry of the insulators is a complex phenomenon [6], [18], [19], [22], [23], [29], [67], [68]. In general, it is agreed that the presence of a water film on the surface of the ice is necessary for flashover to occur [19], [22].…”

Section: Flashover Mechanisms Of Ice-covered Insulatorsmentioning

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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“…A large number of experimental investigations and theoretical studies on the subject of ice accretion on outdoor insulators have been carried out in several laboratories [13][14][15][16][17]. A good survey of the related literature is found in [18].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic investigation of arc over an ice surface /

Nekahi¹

2011

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Ice accumulation on insulators of overhead transmission lines and substations has been recognized as a major problem which may cause insulator flashover and power outages. This phenomenon starts with corona discharge activity and continues with the formation of partial arcs which may result in flashover. Due to the complexity of the process, resulting from surface interaction of discharge with the water film on the ice surface, is not yet fully understood. As for any other type of discharge, the knowledge of some parameters such as temperature and concentration of different species is necessary in order to describe the mechanisms involved. Moreover, to develop mathematical models for discharge propagation, an estimation of discharge channel conductivity is necessary. The current flows through this conductive channel and supplies the energy needed to sustain the ionization activity inside the channel. The conductivity of discharge channel is directly related to its temperature, which illustrates the need for discharge temperature measurements. Up to now, for an arc over an ice surface the temperature has been assumed to have a constant value of 5,000 K, but without any experimental support.The existence of Local Thermodynamic Equilibrium (LTE) is another important aspect for proposing theories and models, but this has not yet been verified for flashover on icecovered insulators. The verification of LTE condition requires information about temperature and concentration of different species, electron density and ionization level.The objective of this research is to augment our knowledge of flashover on icecovered insulators by measuring and calculating several important discharge column parameters. Measurement of rotational and excitation temperatures, and electron density during arc propagation are the first steps. The effect of discharge current, voltage type and polarity on the variation of the mentioned arc parameters should be also studied.Based on these data, the LTE condition could be examined.Spectroscopic plasma diagnostic is a non-destructive test method used to achieve the stated objectives. The emitted light from an arc over an ice surface was transmitted to a spectrometer. The time-resolved recorded spectra of arc were used to study the nature and concentration of ionized species. The gas and electron temperatures and electron densities were also measured using Boltzmann and Stark broadening methods.Measured rotational temperatures were found to vary from 4,000 K to 6,500 K, while the current increased from 200 mA to 700 mA during the discharge propagation. It was observed that under similar experimental conditions, the arc current intensity of DC+ arcs were hotter than that of DC-. Moreover, arc temperatures under AC voltage were lower than those of DC+, and close to that of DC-. The excitation temperature was measured at about 9,000 K and does not vary significantly with discharge current. As current increases, electron densities increased as well. For currents ranging from 200 mA to 700 mA, ...

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Experimental study and analysis of corona discharge parameters on an ice surface

Cited by 43 publications

References 25 publications

Dynamics and modeling of AC arc on surface of ice

Dynamics and modeling of AC arc on surface of ice

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

Spectroscopic investigation of arc over an ice surface /

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