Yazar "Karhan, Mustafa" seçeneğine göre listele

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    A new approach to the analysis of water treeing using feature extraction of vented type water tree images
    (Springer, 2021) Karhan, Mustafa; Çakır, Musa Faruk; Uğur, Mukden
    In this study, vented type water trees were initiated and grown in laboratory environment. A smart test platform was used to accelerate the initiation and growth of vented type water trees. 6 kV/4 kHz voltage was applied to the specimens to initiate and grow water trees. Mel-frequency cepstral coefficients of the vented type water tree images are obtained after 2 h and 10 h of aging respectively. The insignificant regions in the vented type water tree images were removed by using morphological filtering method before MFCC feature extraction. Finally, the statistical values of these features were analyzed. Scatter plots of the standard deviations and mean values of the cepstral coefficients were plotted. As expected, it has been observed that the points in the scatter plot are clustered in a certain area. MFCC is a popular and frequently used feature extraction method in speech recognition, however there are some studies which employs MFCC as a successful feature extraction method in image processing applications. This study provides a new approach to the analysis of vented water treeing using image processing techniques. The other new approach is using MFCC as a feature extraction method in microscopic water tree images.
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    Analysis of electric field and potential distribution of experimental setup for initiating and growing vented type water trees using finite element method
    (Editura Bibliotheca-Bibliotheca Publ House, 2020) Karhan, Mustafa; Çakır, Musa Faruk; Uğur, Mukden
    Water treeing phenomenon has an important and effective role in the service life of polymeric insulators used in the transmission and distribution of electricity. Water trees can be described as permanently localized degradations or damages that can occur in the presence of electric field and humidity. XLPE is widely used as a polymeric insulator material in medium and high voltage cable applications. An experimental setup was prepared to initiate and grow water trees artificially in a laboratory environment and the tests were performed in accordance with the actual values. The electrical and dielectric values of the test material were used for a detailed analysis with high accuracy. The magnitude of the electric field, which was defined by varying the distance between the water needles formed in the XLPE material and the aluminium plate electrode, has been analyzed for various conditions. After laboratory experiments, electric field and potential distribution were simulated and analyzed by FEM (Finite Element Method) using FEMM (Finite Element Method Magnetics) software package. Experiments revealed clearly, that even small changes in the shape of water needle can dramatically affect the electric field and hence the lifetime of the insulator. By using FEMM, both of these parameters (electric field and potential distribution) can be calculated rapidly with high accuracy. HVDC power cables play a significant role in electric power transmission, hence by using the previously described experimental setup, electric field and potential distribution were simulated and analyzed under DC voltage.
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    Investigation of the effects of additives on the electrical and magnetic properties of polyester resin
    (Istanbul University Cerrahpaşa, 2022) Nişancı, Salih; İpekoglu, Mehmet; Nişancı, Muhammet Hilmi; Karhan, Mustafa; Uğur, Mukden
    Polymers are widely used as insulation materials in the electrical industry because their existing electrical and mechanical properties can be altered by adding different types of additives. Successful prediction of the service life of the insulators used in the electrical industry is important for the reliability of the system. For this purpose, insulating materials are subjected to tests according to various standards. In this study, unlike the literature, a polymeric insulator was produced by adding 3 wt.% zinc oxide (ZnO), magnetite (Fe 3O 4), and nickel (Ni) into the polyester. The produced samples were subjected to the inclined plane test in accordance with ASTM (American Society for Testing and Materials) D-2303 standards. In order to analyze the electric and magnetic field distributions formed on the samples during the inclined plane test, first, the current flowing on the samples during the test was measured. Following this, analyses were carried out by creating a simulation model of the samples. Studies found in the literature mainly focus on two-dimensional investigation of the electrical field distribution. This study concentrates on the three-dimensional examination of the electrical field also considering the magnetic field distribution. Results of this study showed that prior numerical analysis gives insight into information about the real-life behavior of the samples.