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Abstract
The quaiity of a power supply is a factor depending not only on the deviation of voltage from its nominal standard but also on the number and type of disturbances that may affect the service.
One important source of disturbances in transmission and distribution systems is lightning which causes permanent or transient faults in overhead lines and distribution systems by direct or more frequently indirect strokes. Lightning may cause damage from sudden voltage increases (line surges), erratic system conditions, insulation failure, crossed power lines and other mishaps.
The reliability of electricity supply systems during thunderstorms is highly dependent on the method of protection against sustained outages.
Lightning is thus becoming a widely researched phenomenon. In order to limit its effects, many protective elements and techniques have been invented and developed to face the damage effect of lightning.
Lightning rods, ground wires, and lightning arresters are now widely used (specially. the latter two elements) in power systems.
There are also new protective elements come into being to help in damping the lightning surges. One of them, which is the main subject of this thesis, is the saturable resistor or shortly saturistor , which has very special nonlinear characteristics.
In this thesis the role of saturistor in surge protection will be extensively studied using MATLAB and MATLAB SIMULiNK. Models for selected arrester and for saturistor with their given characteristics will be developed. A general power system model containing transmission line, underground cable, and a combination of the selected arrester with both the saturistor and a series inductor will be considered.