الفهرس 
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Abstract
The transformer is a vital piece and a major component in any
electrical power system. So, there is a high priority to protect the
transformer against the harmful operating conditions and much attention is devoted to keeping it in optimum shape. When the transformer energized high peak, current is observed. The mentioned current called inrush current. This transient current can ‗‘inrush current‘‘ rise to six or eight times the rated current, and
transformer users are always apprehensive about its repeated switching. Some reference says that inrush current can reach up to 10 times of the normal rated current. It has high magnitude and harmonic rich.
Inrush current have undesirable effects on the power transformer due to asymmetry of core flux during energization. The undesirable effecting includes protection relay mis-operation, melting fuse and lifetime of transformer. Several techniques used to mitigate and reduce inrush current such as controlled switch and insertion resistor …etc.
This thesis presents the basic principles, fundamental theory of transformer inrush current and investigates some methods and techniques for mitigation
and controlling inrush current magnitude in high voltage substation
transformers. Number of factors effecting on the magnitude of inrush current on transformer are described in brief. The software package (MATLAB/SIMULINK) is used to carry out the work in this thesis as a simulation tool to estimate and mitigate the transformer inrush current in high voltage substation transformers. Different techniques to mitigate inrush current in transformer are applied and studied. The simulation results obtained using the different techniques are compared with each other.