Contribution à l’étude des performances des parafoudres à base d’oxyde de zinc soumis à des contraintes transitoires rapides dans les systèmes électriques

Abstract

The aim of the work exposed in this thesis relates to the modelling and the study of the protection performances of metal oxide surge arrester (ZnO) in a real network when fast front transient overvoltages are present. To carry out this objective, a new technique based on genetic algorithms for the identification of ZnO surge arrester models parameters is developed. It was tested on a modified version of the IE recommended model that we have proposed. The results obtained are very satisfactory and the proposed technique can be used for the automatic identification of the parameters of any ZnO arrester equivalent circuit. A more exact calculation of inductances on the structures of metal oxide surge arrester is developed. This calculation of inductances is based on analytical formulas. The formulas presented take into account all possible practical arrangements of the installations of surge arresters. This study was made to overcome the insufficiencies observed in preceding work where inductance was estimated by multiplying an inductance per unit length by the length of the lead wire or the height of the surge arrester. An example of application was implemented in the EMTP (Electromagnetic transients program) and satisfactory results were obtained. The study enabled us to take into account the effect of the angle between the lead wire and the busbar. The effect of the inductance of surge arrester structures on the problem of the overvoltage protection was outlined. The analysis of the dynamic protection performances of ZnO surge arrester on an HV network was carried out. The proposed modified version of the IEEE recommended model was introduced. Its parameters were identified by using the technique developed in this thesis. The operational substation El-Hassi of Setif which is used as an example was represented by a three-phase complete diagram. Resulting overvoltages in several fundamental points were presented and discussed. The specialized software EMTP (Electromagnetic transients program) was used for this purpose.