Review Article
Abugalia A
Abstract
Different protective devices types based on previous literature are discussed. Special attention is focused on metaloxidesurge arresters, their non-linear characteristics, models, factors affects on protective characteristics, effect andbehavior in working conditions. The paper presents the analysis of the influence of non-linear characteristic of protectivemetal-oxide arrester on the overvoltage shape appeared on the protected transformer. The characteristic of the arresteris approximated by power type function. As an example the overhead transmission line connected to transformerthrough a busbar is considered. The line is characterized by their surge impedance and travel time and the transformerby its surge impedance. The transformer is protected by protective device such as metal-oxide arrester connected inparallel with it. The system of equations describing the overvoltage transmission line, transformer and the protectivedevice modeled by non-linear v-i characteristic, based on digital step-by-step solution is written. The computer modelingsoftware is used to solve the equations and compute overvoltage’s waveshape at transformer. The (v-i), (v-t), and (i-t)characteristics obtained as the result of these computations are presented.