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HTS transformer windings design using distributive ratios for minimization of short circuit forces
, Article Journal of Superconductivity and Novel Magnetism ; 2018 ; 15571939 (ISSN) ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Springer New York LLC
2018
Abstract
High-temperature superconducting (HTS) transformers have a promising feature in reduction of total weight, total size, and the losses of large-scale distribution transformers. However, the lower leakage reactance of HTS transformers results in a higher short-circuit fault currents and electromagnetic forces. Therefore, optimization of short-circuit electromagnetic forces is one of the crucial aspects in the design of HTS transformers. In this paper, a novel analytical method is proposed for determination of optimum distributive ratios resulting in minimization of these forces for asymmetrical multi-segment windings of an HTS transformer. Employing these distributive ratios, radial and axial...
Multi-segment winding application for axial short circuit force reduction under tap changer operation in HTS transformers
, Article Journal of Superconductivity and Novel Magnetism ; Volume 32, Issue 10 , 2019 , Pages 3171-3182 ; 15571939 (ISSN) ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Springer New York LLC
2019
Abstract
High-temperature superconducting (HTS) transformers have remarkable appealing advantages over conventional ones. But higher brittleness of HTS windings with respect to copper windings makes HTS transformers more vulnerable in short circuit and inrush current situations. During tap changer operation, appreciable asymmetry and non-uniform distribution of ampere-turn along the windings causes high axial component of short circuit forces and makes the situation more severe. In this paper, multi-segment winding method is employed for reduction of axial short circuit forces. An analytical method is presented for calculation of axial component of short circuit forces under tap changer operation....
HTS transformer windings design using distributive ratios for minimization of short circuit forces
, Article Journal of Superconductivity and Novel Magnetism ; Volume 32, Issue 2 , 2019 , Pages 151-158 ; 15571939 (ISSN) ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Springer New York LLC
2019
Abstract
High-temperature superconducting (HTS) transformers have a promising feature in reduction of total weight, total size, and the losses of large-scale distribution transformers. However, the lower leakage reactance of HTS transformers results in a higher short-circuit fault currents and electromagnetic forces. Therefore, optimization of short-circuit electromagnetic forces is one of the crucial aspects in the design of HTS transformers. In this paper, a novel analytical method is proposed for determination of optimum distributive ratios resulting in minimization of these forces for asymmetrical multi-segment windings of an HTS transformer. Employing these distributive ratios, radial and axial...
Short Circuit Force Evaluation in 3D Core Distribution Transformers
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
The work starts with comparison of 3D-wound core transformers against the conventional transformers using the published research results. The past works on transformer short circuit force calculation are reviewed. An algorithm is developed to design 3D-wound core distribution transformers. To determine the maximum short circuit forces, currents in different type of short circuits have been calculated. The worst case in different core configurations and different type of winding connections is determined. Different analytical methods are investigated for transformer short circuit force calculation. Two-dimensional and three-dimensioal finite element methods (using Comsol software) employed to...
Optimal Multicriteria Design of HTS Transformer and Construction of a Laboratory Scale Sample
, Ph.D. Dissertation Sharif University of Technology ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Co-Supervisor) ; Hekmati, Arsalan (Co-Supervisor)
Abstract
Employing high-temperature superconducting (HTS) tapes, instead of copper or aluminum wires for winding in a superconducting transformer, results in a series of significant advantages; such as: smaller volume, lighter weight, higher efficieny, greatly extended overload capability, better voltage regulation, lower life cycle cost, fault current limiting capability, lower environmental pollution and lower risk potential against fire hazards.In this thesis, optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers has been performed. Then, multilayered flux diverters have been proposed for reduction of weight and losses. The impact of...
Design of a SF6 Load Breaker Switch for Compact Distribution Substation
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
Electrical energy customer and load growth on the one hand and the problems of allocation of land for the development of the power networks on the other hand, make the tendency to use less space in the electrical industries. One of the solutions used in power distribution networks, especially in crowded areas is compact substation which requires less space than ordinary substations and also the prefabricated types of this substation can be used in the distribution system. In a compact distribution substation, all components must be designed with a minimum size. Therefore, the insulation system of the compact substation should be designed based on these requirements.
In the distribution...
In the distribution...
A new multi-winding traction transformer equivalent circuit for short-circuit performance analysis
, Article International Transactions on Electrical Energy Systems ; Vol. 24, issue. 2 , 2014 , pp. 186-202 ; ISSN: 20507038 ; Vakilian, M ; Faiz, J ; Sharif University of Technology
Abstract
Current and force calculations in different short-circuit conditions are required for short-circuit performance analysis of a multi-winding traction transformer which is one of the most important requirements in its design process. This paper extends the available low-frequency three-winding star equivalent circuits to develop a novel equivalent circuit for the four-winding traction transformers. The leakage inductances of the traction transformer are determined and employed to calculate the parameters of this developed star model. It is shown that the star equivalent circuit is a valid and appropriate model to simulate the steady-state and dynamic performance of the traction transformer...
HTS transformers leakage flux and short circuit force mitigation through optimal design of auxiliary windings
, Article Cryogenics ; Volume 110 , September , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Mitigation and control of leakage fluxes and short circuit forces needs much more attention, for a high-temperature superconducting (HTS) transformer, than for a conventional one. Different methods such as the application of auxiliary windings, multi-segment winding, and flux diverter have been presented in the literatures for leakage magnetic field reduction in HTS transformers. In this paper, for the first time, optimal design of auxiliary windings has been performed for a 132/13.8 kV, 50 MVA three phase core type HTS transformer. Genetic algorithm (GA) has been used for the optimization process. Induced current in auxiliary windings which is inversely proportional to the leakage fluxes...
Optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers
, Article IEEE Transactions on Applied Superconductivity ; Volume 30, Issue 1 , January , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The appealing advantages of high-temperature superconducting (HTS) power transformers over conventional ones have attracted transformer manufacturing companies, power companies, research institutes, and universities worldwide to conduct research and development in this field. Unfortunately, HTS transformers are more vulnerable to mechanical stresses than conventional transformers. The results of the interaction between current carrying windings and leakage magnetic fluxes are the electromagnetic forces, which act on transformer windings. Under short circuit events, these forces are remarkable, and, therefore, catastrophic failure of transformer may arise. Flux-diverter applications have been...