Comparison between AC and DC flashover performance and discharge process of ice-covered insulators under the conditions of low air pressure and pollution

Shu, Lichun; Shang, Yunlong; Jiang, Xingliang; Hu, Qin; Yuan, Qing; Hu, Jianlin; Zhang, Zhijun; Zhang, S.; Li, Ting

doi:10.1049/iet-gtd.2011.0300

Cited by 19 publications

(8 citation statements)

References 14 publications

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“…The results showed that when the water film appears, the air gap at the high-voltage end bears most of the voltage drop, exceeding 50%. At this time, the local arc is always first generated in the air gap at the high-voltage end, which is consistent with the observation of ice-covered insulators flashover test [13,19,20]. Moreover, when the local arc appears, the water film conductivity will further affect the residual ice resistance, and consequently, impact the flashover performance of ice-covered insulators [21].…”

Section: Effect Of Water Film Conductivity On Electric Field Of Icecosupporting

confidence: 83%

Three‐dimensional electric field simulation and flashover path analysis of ice‐covered suspension insulators

et al. 2020

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Flashover of ice-covered insulators seriously affects the safe operation of transmission lines. It is necessary to study the electric field distribution for flashover analysis of ice-covered insulators. The electric field of ice-covered insulators was mostly calculated by a two-dimensional (2D) axisymmetric model that cannot be well corresponded to actual icing situations. In this study, a 3D electric field simulation model of ice-covered suspension insulators under moderate icing condition with applied DC voltage was established. Two characteristic parameters, E av and E max were proposed to measure electric field distortion degree. Based on the simulation results, the effects of water film conductivity, icicle length, icicle deviation angle, and icicle distribution on E av and E max were studied. The results showed that icicles have a significant influence on the electric field distribution of insulators. E av increases with the increase of icicle length and decreases with the increase of icicle deviation angle. E max increases with the increase of the icicle length, icicle spacing and adjacent icicle length difference. When the icicle deviation angle is 45°, E max is the largest. Lastly, the possible flashover paths were analysed based on the simulation results, which would provide a theoretical basis for building a flashover model of ice-covered insulators.

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Section: Effect Of Water Film Conductivity On Electric Field Of Icecosupporting

confidence: 83%

Three‐dimensional electric field simulation and flashover path analysis of ice‐covered suspension insulators

et al. 2020

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“…Jiang et al [146] determined the relationship between the AC minimum flashover stress of an ice-covered insulator string including nine IEC standard suspension units and ISP as per the U-shaped curve method. A series of AC and DC flashover tests on porcelain, glass and composite insulators was carried out using melting regime method by Shu et al [145]. The relations between the flashover stress and ISP were extracted from AC and DC test results obtained from an insulator string of seven porcelain units.…”

Section: Flashover Results Presentation Using Icing Stress Product (Isp)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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“…Although many previous studies have focused on the effect of electric field on insulator icing process, most of them are based on a single case, the comparison of the traditional insulator and (super-)hydrophobic insulator is relatively few [22][23][24]. The influence rule of electric field on the ice-coating process of insulators with different dielectric surfaces needs to be further studied.…”

Section: Introductionmentioning

confidence: 99%

Influence of electric field on the ice‐coating process of insulators with a different dielectric surface

Yang

Jiang

Huang

et al. 2020

IET Science, Measurement & Technology

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Comparison between AC and DC flashover performance and discharge process of ice-covered insulators under the conditions of low air pressure and pollution

Cited by 19 publications

References 14 publications

Three‐dimensional electric field simulation and flashover path analysis of ice‐covered suspension insulators

Three‐dimensional electric field simulation and flashover path analysis of ice‐covered suspension insulators

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

Influence of electric field on the ice‐coating process of insulators with a different dielectric surface

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