الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Insulation system in high voltage power equipment plays a significant role for the reliability of the electric power system. As a result, it is necessary to assess its performance to prevent any sudden interruption in the power system. High voltage transmission lines are commonly referred to as the backbone of electrical power systems due to their spatial distribution and large power capacity. Outdoor insulators are the most effective component of the electric power transmission and distribution systems subjected to various defects under operating and environmental conditions. They are to be installed in the overhead transmission lines to serve two important tasks: first, to isolate the electricity represented in conductor from the grounded tower structure and second, to be as mechanical support for the conductor. In order to perform their functions successfully, they should have good electrical, mechanical and thermal properties. Failure of a single insulator can lead to an outage of the power network. As a result, it is necessary to check their condition regularly to achieve a maximum possible reliability for the system, to prevent any sudden interruption in the power system, to decrease the power loss and to evaluate the maintenance priorities needed to insulators. Defective discs of ceramic insulators essentially contain partial discharge (PD) activities; i.e., the presence of PD activities may characterize the insulator’s poor condition.
Partial Discharge detection and measurement is considered the most significant phenomena to be subjected in the performance assessment of insulation diagnostics. Partial discharge is a localized discharge event that does not bridge the distance between two conducting electrodes inside an electrical insulating material under electric field stress. PD in solid dielectrics could occur due to the presence of a cavity or a crack within the insulating material which could be formed during manufacturing, installing or/and operating conditions. So, defects in high voltage insulators could cause partial discharge which can lead to causing deterioration of the insulation system and consequently a complete failure may be occurred.
The detection of radio frequency (RF) waves emitted from the PD activities is an emerging technique to monitor the insulator’s condition during its operation. In this thesis, various artificial defects are introduced to the insulator discs and the corresponding RF signatures are captured using a high frequency sensor under the normal operating voltage. Signal processing techniques are introduced to the captured RF signatures for further analysis. An Artificial Neural Network (ANN) is used for training of an intelligent classifier that is used for identifying the type of the insulator defect.
Also, this thesis introduces a theoretical modeling and simulation of PD resulting from internal cavities with variable sizes within rubber solid dielectric material. For that purpose, COMSOL Multiphysics program is used as a finite element analysis (FEA) tool which is interfaced with MATLAB software. Furthermore, a comparison study is introduced between simulated and measured results based on the charge magnitude value.
In addition to that, statistical analysis tools are performed on the RF signatures obtained from the tested insulators in order to ensure the normality and homogeneity of the tested samples. Furthermore, quality control charts are introduced to show that the obtained data are under control or not, and to be used as a classification tool for defective insulators.