Modélisation dynamique des décharges sur les surfaces d'isolateurs pollués sous différentes formes de tension: élaboration d'un critère analytique de propagation

This work presents a self-consistent discharge model allowing to predict the behaviour of polluted insulators under different voltage waves (DC, AC and impulse). This model is based on an electroenergetic considerations and uses the physical characteristics of the arc and an equivalent electric circuit. A new analytical propagation criterion of the discharge is firstly established. Then, an autonomous dynamic model describing the temporal evolution of the discharge is developed. It enables to determine the critical parameters of the discharge such as the current evolution, the corresponding charge, the potential gradient in the channel, the arc length and its resistance, the flashover voltage and the time lag to flashover. The insulator geometry, the current constriction on the arc foot, the arc radius variation and the instantaneous velocity of the discharge are taken into account. The simulated results given by the model are in a good accordance with the experimental ones. The proposed model is also discussed with regards to those reported by other investigators.Ce travail présente un modèle de décharge permettant de prédire le comportement d'un isolateur pollué soumis à différents types de tensions. Ce modèle est basé sur des considérations énergétiques et utilise les caractéristiques physiques de l'arc ainsi qu'un circuit électrique équivalent. Un nouveau critère analytique de propagation de la décharge faisant intervenir l'impédance équivalente d'un circuit électrique simulant un isolateur pollué sur lequel une décharge s'est produite, est présenté. Pour tenir compte de l'évolution du phénomène de propagation de la décharge dans le temps, un modèle dynamique autonome est développé. Ce modèle permet de calculer la tension de contournement des isolateurs et de décrire la dynamique de l'arc en tenant compte du changement de la résistance de l'arc, du profil de l'isolateur, de la constriction des lignes de courant au pied de la décharge, de la variation du rayon de l'arc, de la vitesse instantanée de propagation de la décharge et du type d'onde de tension appliquée (continue, biexponentielle ou alternative). Les caractéristiques obtenues à partir du modèle sont conformes aux observations et mesures effectuées en laboratoire

Predictive dynamic model of the leakage current and flashover voltage of discontinuously polluted insulators under ac voltage: experimental validation

International audienceThis paper is aimed at the determination of the leakage current and the flashover voltage of discontinuously polluted insulators submitted to ac voltages, using a predictive dynamic model based on an equivalent electrical network. This model is an extension of the one we developed for uniformly polluted insulators. The influence of the width and conductivity of polluted layers is investigated. The simulated results are validated experimentally on a plane insulator model using electrolytic solutions of different conductivities

Self-consistent multi-arcs dynamic model for high voltage polluted insulators

International audienceThis paper presents a self-consistent multi-arcs dynamic model for high voltage polluted insulator under impulse voltage. This model is an improvement of that one developed for single arc; it is based on an electrical equivalent circuit consisting of a series of different partial arcs and residual layer resistance. It takes into account the configuration of insulator, applied voltage polarity and the instantaneous changes of discharges parameters. The proposed model enables to compute the flashover voltage and leakage current and to show the influence of dry bands on the voltage distribution along the surface and furthermore on the electrical performance of polluted insulator. It is validated using a simple plane model in the case of uniform and non-uniform polluted bands. The computed flashover voltage and leakage current are found in good agreement with those measured experimentally

A new proposal model for flashover of polluted insulators

Plein texte sur le site de l'éditeur : http://www.iop.org/EJ/abstract/0022-3727/30/5/022International audienceIn this paper, the principal pollution flashover models are reviewed and then an impedance criterion for are propagation is proposed. This criterion differentiates the case in which the are elongates until total flashover occurs from the case in which the are stops before it reaches the end of the insulator. It is shown that the Hampton criterion is not a sufficient condition for initiation of the are. Indeed, the latter can expand, under certain conditions, even if the Hampton criterion is not satisfied. An analytical model allowing one to determine the critical voltage that insulators can withstand is also established. This is based on an energetic balance, an equivalent electrical circuit and the physical characteristics of the are. The critical voltage, the critical current and the critical are length for polluted insulators are calculated using the elaborated model. The results so obtained are found to be in accordance with the experimental ones represented by known empirical relations

Influence of dry bands on polluted insulator performance

International audienceThis paper is aimed at the study of the influence of dry bands and the pollution distribution on insulator performance under impulse voltage. For that purpose, numerical simulation of electrical field and potential distribution along high voltage insulator model with different configurations of pollution layer is performed. Simulation results have showed that the increase of dry bands may improve the potential grading. The flashover voltage and critical leakage current for uniform, non uniform, continuous and discontinuous distributions of pollution deposits on insulator are also computed using a multi-arcs dynamic model. The computed results are found in a good accordance with the experimental ones

Review of predictive surface discharge modeling over a solid insulator based on the equivalent electrical circuit

This paper presents the application of the equivalent electrical circuit for the predictive modeling of the dynamic of surface discharge and flashover of solid insulators. Both of dry insulator and polluted insulator models and application are presented. The results show that this model is useful for a better understanding of the flashover mechanism and the design of the insulation level for high voltage electrical equipment