Abstract
This paper presents the development of a new bi-arc dynamic numerical model for predicting AC critical flashover voltage (FOV) of ice-covered extra-high voltage (EHV) insulators. The proposed model is based on a generic calculation algorithm coupled with commercial finite element method software designed to solve the Obenaus/Rizk model. The proposed model allows one to implement the Nottingham and Mayr approaches and compare the results obtained as a function of the arcing distance, the freezing water conductivity, and the initial arc length. The validation of the model demonstrated high accuracy in predicting the FOV of ice-covered post-type insulators and its capability to simulate the interaction of the two partial arcs during the flashover process. In particular, the results showed that the Nottingham approach is sensibly more accurate than the Mayr one, especially in simulating the dynamic behavior of the partial arcs during the flashover process. Based on the encouraging results obtained, a multi-arc calculation algorithm was proposed using the bi-arc dynamic numerical model as a basis. The basic idea, which consists in dividing the multi-arc model in several bi-arc modules, was not implemented and validated but will serve as a promising concept for future work.
Highlights
Flashover of line and post insulators due to atmospheric ice accretion still constitutes a cause of failure of overhead electrical power transmission systems in cold climate regions
Several studies performed on this topic demonstrate that the flashover process is an extremely complex phenomenon, which depends on the interaction between the partial arcs established along the air gaps, the condition of the ice surface, the environmental conditions, and the arcing distance of the insulator [1,2,3,4,5,6,7,8,9,10,11]
Energies 2018, 11, 2792 applicability of the static and dynamic predictive models to insulators having an arcing distance lower than 1 m [12,13,14,15,16,17,18]. To avoid such a limitation, some authors have proposed an improvement of the original Wilkins formulation in order to determine the residual resistance when several partial arcs and, several arc roots are in contact with the ice surface [14,18]
Summary
Flashover of line and post insulators due to atmospheric ice accretion still constitutes a cause of failure of overhead electrical power transmission systems in cold climate regions. Energies 2018, 11, 2792 applicability of the static and dynamic predictive models to insulators having an arcing distance lower than 1 m [12,13,14,15,16,17,18] To avoid such a limitation, some authors have proposed an improvement of the original Wilkins formulation in order to determine the residual resistance when several partial arcs and, several arc roots are in contact with the ice surface [14,18]. The initial numerical model proposed was based on the Obenaus/Rizk single arc model, which was solved using the finite element method (FEM) to compute the E-field distribution between the arc root and the ground electrode, the leakage current as well as the residual resistance of the ice surface for a defined applied voltage The accuracy of this new predictive model was significantly improved for FOV results obtained with single arc mathematical models without previously associated geometrical limitations thanks to FEM. The proposed bi-arc dynamic numerical models proposed in this paper represent a great improvement over actual mathematical multi-arc models, which are confined to simple geometries without providing accurate and convivial numerical tools for outdoor insulator dimensioning
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