Contribution à l’étude de la coordination des isolements des postes de transformation haute tension basée sur l’emploi de parafoudres ZnO

Abstract

Insulation coordination is defined as the selection of the dielectric strength of equipment in relation to the voltages which can appear on the system for which the equipment is intended and taking into account the service environment and the characteristics of the available protective devices. In an insulation coordination study, the voltage levels of power system equipment are determined in order to ensure the protection of equipment against overvoltages. In this thesis, an insulation coordination study is performed for lightning overvoltages in 400 kV substations in Algeria High Voltage Electricity System. Several approaches have been proposed to study the overvoltages caused by lightning strokes that impact a line connected to a substation. Regarding the random nature of the lightning phenomenon, the procedure must be statistical and generally the Monte Carlo method is used as the solution for this type of studies. In the first part, a statistical method based on Monte Carlo technique for evaluating lightning performance of a complete air insulation substation (AIS) using the capability of simulation tools is presented. This technique has been coded in MATLAB and linked to EMTP/ATP program to perform the network simulations. The simulations are carried out considering several protection scenarios. It is corroborated that the installation of ZnO arresters at line input and in the vicinity of the autotransformer gives an acceptable mean time between failures (MTBF) at different points in the substation and then provides an adequate protection. Although the studies presented in the second part were aimed at estimating substation equipment MTBF, the procedure can also be used to select surge arresters or substation BILs, once the desired MTBF is fixed and arrester locations have been selected, the surge arrester ratings can be selected by following the detailed procedure; only those surge arresters with which the MTBF exceeds the specified value should be considered. The parallel computing feature of MATLAB has permitted a more accurate prediction of the overvoltages at different points in the substation and significantly reduces the CPU run time of the overall solution process