Study of the behaviour of a protection installation based on a varistor in electrical installation

The objective of this article is the study of the varistors based on zinc oxide (ZnO) as nonlinear elements used for the protection of an electric installation against the transitory phenomena which can brutally emerge in the course of time. The transport of electric power requires the use of the lines and the cables where the transitory phenomena are propagated. First, the authors established the equivalent model of the lines while based on the theory of the lines. Since the application requires the knowledge of the linear parameters of the line, they present a method for the calculation of these elements. Based on the model of the two blocks, they formulated the problem starting from the diagram of an electric installation. Using this model, they established the equations of propagation of this phenomenon. These equations are solved by a numerical calculation program written in FORTRAN 77, and which is based on a temporal approach using Laplace inverse transformation.