Browsing by Author "Najafi, Atabak"

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Comparison of Derating in Transformerunder Non-Linear Load and Imbalanced Supply Voltage Based on Tsfem
(Konya Technical University, 2020) Najafi, Atabak
Distribution transformers which are widely used in industry and distribution centers are themost affected by voltage imbalance and harmonic loads. These situations have a negative impact onefficiency , core loss and winding loss of distribution transformers, In this article, derating as well as lossesincrease of transformer under non-linear loads and imbalanced supply voltage conditions are examined .harmonic loss factor (HFL) and K-factor have been used to perform the transformer derating. In this study,3D time-step finite element method(TSFEM) used to observe the magnetic flux density formed in thewindings and core of the distribution transformer. According to the results obtained, it is seen that theIEEE standard is insufficient for the derating of the transformer under high harmonic current (THDI) andunbalanced conditions and Time Stepping Finite Element Method is a more suitable method.
An Economic and Technical Review for the Utilization of Hvdc in Turkey and in the World
(Konya Technical University, 2021) Acaroğlu, Hakan; Najafi, Atabak; Kara, Ömer; Yürük, Burcu
In recent years, it is seen that High Voltage Direct Current (HVDC) transmission line systems have come to the fore in the field of energy efficiency in the world. Therefore, it is predicted that analyzing the technological and economic advantages of HVDC transmission line systems will make an important contribution to energy efficiency policies. In this regard, this study aims to examine the technological and economic advantages of HVDC transmission systems through the historical development with applications in Turkey and in the world. In addition to this, it is expected that the evaluation of the effects of energy efficiency on the economy will bring a different perspective to the energy and economic literature. Therefore, it is thought that energy and economic policies for the spread of HVDC transmission line systems worldwide will be essential. The asymmetric distribution of natural energy sources in the world causes energy supply security problems in the countries such as Turkey in terms of high foreign dependence on energy. For this reason, it is necessary to meet the increasing energy demand and increase the existing capacity day by day. Besides, it is important to develop policies for efficient use of energy.HVDC technology is extremely important for a developing country like Turkey. Moreover, it is known that this energy transmission technology has become widespread in developed countries. Thereby, a technical comparison is done for investment costs of the transmission system in Germany. As a result, other than bringing economic benefits with the energy transmission of Turkey through HVDC, it has important potential for making energy transmission possible with her neighbors and European Union countries.