Contribution to the study and analysis of the metal ‎oxide surge arresters failure

Abstract

The first part of this thesis is aimed to improve the distribution of the potential and the electric field along a 220 kV ‎polymeric surge arrester by optimizing the design of the grading ring. A combined method based on 3D-FEM and ‎Taguchi design is opted in order to obtain the objective function. The optimal design of grading ring is achieved by ‎minimizing the electric field along the active column of varistors using a reduced number of simulations based on the ‎Taguchi design and a bat algorithm. By the use of an optimal design of the single ring, the electric field is reduced by ‎‎42% in the top of the 220 kV metal oxide surge arrester. Then, it was proposed to install an additional ring at the top of ‎the metal oxide surge arrester in order to obtain a better distribution of the potential and the electric field along the ‎active column. This proposed additional ring has a large geometric dimension compared to the first ring. Simulation ‎results show that using an optimal design of double rings, the potential distribution can be made as uniform as possible ‎and the electric field is reduced by 53% to avoid damage of varistors. ‎ The second part of the thesis concerns the electro-thermal modeling of metal oxide surge arresters which allows the ‎temperature variation of the studied ZnO surge arrester. For this purpose, an electro-thermal model formed of heat ‎source, capacitances, and resistances was derived. The equivalent circuit of this model has been implemented in the ‎ATP / EMTP software in order to simulate the internal temperatures of the varistors and the external temperatures of ‎the surge arrester housing, and satisfactory results have been obtained. The suitable evaluation of the temperature ‎would allow us to monitor the condition of the surge arrester as well as to avoid its failure.‎