LEE- Elektrik Mühendisliği-Doktora
Bu koleksiyon için kalıcı URI
Gözat
Konu "Electric power" ile LEE- Elektrik Mühendisliği-Doktora'a göz atma
Sayfa başına sonuç
Sıralama Seçenekleri
-
ÖgeDevelopment of a new reliable analytical technique for the determination of the leakage reactance in the power transformers(Graduate School, 2022-09-14) Dawood, Kamran ; Kırış Kömürgöz, Güven ; 504172005 ; Electrical EngineeringThe transformer plays a critical role in the distribution and transmission of electric power. Transformers are also one of the most essential pieces of equipment to reduce power losses during electricity transmission. To provide reliable energy to the power consumers, the transformer must be designed properly to operate in different conditions and all international standards must be also fulfilled during the designing and manufacturing of the power transformer. Leakage reactance is one of the most crucial characteristics to consider in the electromagnetic design of a transformer. The majority of failures of power, tap-winding and converter transformers are due to the short-circuit conditions in the windings. One of the main parameters during the design of transformers is leakage reactance and analysing this parameter in a cheaper and faster way is one of the main objectives of the transformer designers. When the short-circuit occurs, a higher current is generated in the windings of the transformer. The higher short-circuit current not only affects the working of the transformer but also affects the other parts of the transformer. Short-circuit current also affects the lifespan of the transformer. The short-circuit current in the transformers can also be easily evaluated by evaluating the leakage reactance and leakage inductance properly. Analytical techniques and experimental results are two main methods for calculating the leakage reactance. If the calculated leakage reactance of the transformer is higher than the actual leakage reactance and if the transformer is designed according to the calculated value, a transformer cannot withstand the short-circuit condition and can result in failure. On the other hand, if the calculated leakage reactance of the transformer is less than the actual leakage reactance, more material will be used for the manufacturing of the transformer, and the transformer will be heavier, more expensive and bigger. So, finding the accurate value of the leakage reactance is crucial for the manufacturer of transformers. Stability, efficiency and reliability of the transformer also mainly depend on the leakage reactance of the transformer. The manufacturing costs of the transformer can also be minimized by calculating the leakage reactance ideally. Therefore, a proper prediction of the leakage reactance in the power transformer is needed to implement an optimized design. The main aim of this research is to analyze and optimize the leakage reactance in the different types of transformers using a finite element method technique. Different analytical methods are presented in this thesis to evaluate the leakage reactance. The leakage reactance of the symmetric winding transformer and the asymmetric winding transformer is examined using a finite element method, analytical methods, and the experimental method. More than five different real cases are studied during the evaluation of the leakage reactance in the symmetric winding transformer and the asymmetric winding transformer. In this work, abnormalities in the analytical calculation of the leakage reactance in the asymmetric windings will be also identified. In order to take the winding height effect into the account, this work will also propose a correction to the analytical formulation for the calculation of the leakage reactance in the asymmetric. Tap winding transformers are one of the widely used techniques to achieve the different voltage levels on the single or both sides of the transformer. This thesis has also presented a finite element technique to examine the leakage impedance in the two-winding and three-winding tap transformers for three different voltage levels. This study presents first-time finite element models for the evaluation of the leakage impedance in the tap winding transformers and compares them with the experimental results, which will add great value to present research and help manufacturers to optimize the design of the tap winding transformers. Other important aspects such as core losses and magnetic flux density are also examined using the finite element method. Leakage reactance is also one of the most important parameters of the zigzag transformers. The accurate prediction of the leakage reactance also minimizes the cost of the zigzag transformer. Therefore, the prediction of leakage reactance in the zigzag transformer using analytical or numerical methods is an essential part of the early designing stages of the transformer. In this thesis, leakage reactance in the zigzag winding transformer is also determined using the finite element technique. The prototype zigzag transformer is also manufactured and tested to verify the accuracy of the finite element method for the evaluation of the leakage reactance. Converter transformers are widely used in the electric transport system and it is crucial equipment for a rectifier unit of the transport's tracking substations. Leakage reactance is one of the main criteria during the development of a converter transformer. In some of the converter transformers, windings and other parts of the transformer are so complex that analytical methods are impossible or very difficult to implement, and hence any other method is needed to calculate the different parameters of the transformer. In this thesis, to optimize the design of the electric transport system transformer, a finite element analysis is used to evaluate the leakage reactance. A prototype converter transformer of the electric transport system has been developed to obtain the experimental results. The results of the different analytical and finite element methods are also compared with the experimental results. Additionally, this thesis will also propose a new analytical method for the calculation of the leakage reactance for the symmetric winding transformer and asymmetric winding. As presented in the thesis, there are many analytical techniques for the determination of the leakage reactance in the different types of transformers. However, the majority of the analytical methods are applicable to the transformers with the same axial heights of the low voltage and high voltage winding (symmetric windings). To improve the accuracy in the analytic computation of the leakage reactance in the transformers, especially for the asymmetric; a new analytical method is proposed to calculate the leakage reactance in the asymmetric windings more appropriately. The analytical technique for the calculation of the leakage reactance is proposed with the help of the difference between experimental tests with previous analytical methods and finite element method results. The new proposed analytical method will reduce the time of the modelling and simulation of the transformer, provide a solution for the calculation of the leakage reactance in the two-winding transformers and does not require significant amounts of finite element programming and simulation time. Therefore, a proposed analytical method can give quick and easy results for leakage reactance. Results also prove preliminarily the efficiency, simplicity, feasibility and validity of the new analytical technique for the calculation of the leakage reactance and its ability to provide the transformer designers with a new reliable and simple method to calculate the leakage reactance accurately and to develop transformer properly.