Design Of Power Transformers Research Articles

Electromagnetic–Structural Finite Element Analysis of Copper and Aluminum Windings in Power Transformers under Short-Circuit Conditions

Electromagnetic forces can lead to the structural failure of power transformers due to extreme loading conditions, vibration, and/or fatigue. Therefore, studying the nature and the magnitude of these forces is a key task in the design and failure analysis of such important equipment. Keeping this issue in mind, this work aims at conducting a numerical analysis in order to evaluate the mechanical stresses and displacements of windings in power transformers due to the action of electromagnetic forces. With this purpose, a finite element model is developed considering electromagnetic and mechanical effects assuming short-circuit conditions. The study compares the cases employing copper and aluminum windings with header tap, in different temperatures. The model developed in this work is verified against analytical solutions. The numerical calculations allow for performing a detailed analysis in terms of the distribution of both displacements and stresses along the windings, which is of great relevance for identifying critical structural points and avoiding structural failure. Overall, the obtained results demonstrate that the finite element model is a useful tool for the structural design of power transformers that allow for investigating and optimizing key aspects before manufacturing.

Design and testing of an arc resistant power transformer with a reinforced turret

This paper presents the design and testing of a full-scale 510-kV, 415-MVA HVDC converter transformer prototype designed to withstand the resulting pressure of a 20 MJ low-impedance fault in oil occurring inside a bushing turret, which is one of the major causes of transformer fires. In addition, there is currently few studies and recommendation regarding this failure mode, which is the main motivation for initiating this study. In total, two full-scale units were designed and built: First consisting of a reinforced turret and a transformer tank designed for arc resistance using nonlinear static finite-element analysis with design pressures retrieved from explicit dynamic simulations, and a second reference unit, with a conventional turret design. Both units were then experimentally tested with a methodology based on injecting pressurized air into the water-filled units, with test equipment dimensioned and calibrated to achieve a linear injection of energy equivalent to a 23 MJ arc in oil in 100 ms. The reinforced turret and transformer tank was able to contain the arc energy and performed as predicted by the nonlinear static and explicit dynamic simulations. The energy levels used in tests are, to our knowledge, the highest reported for a low-impedance fault occurring inside a turret, demonstrating the feasibility of designing a transformer to safely withstand mentioned faults without rupturing. The suggested reinforced turret is a robust and maintenance free solution offering passive protection against internal arcing, without the need of additional relive devices. It will significantly reduce the risk of fires, improve overall safety of the substation, and has the potential to be optimized for different arc energy levels and voltage class for turrets, cable boxes and chimneys.

Optimization of Core Loss for Power Transformer Using Taguchi Method

This article focuses on the optimization of process parameters such as core area, core material and voltage for the design of power transformer. It employs Taguchi orthogonal array technique for designing the experiments and its analysis. Utility transformers are usually specified with the losses associated at design stage. The area of the core cross-section applied voltage, as well as the core material all has impact core loss deterioration. The impact of such variables influencing core loss is investigated by executing the model. A small proportion of core as well as the coil assembly experiments is simulated using the Taguchi approach with the orthogonal array. In this study, the core as well as the coil assembly of an 8MVA, 33/11KV, 3 Phase Transformer is modelled in ANSYS MAXWELL software. MINITAB software is used to assess the program's anticipated core loss in order to discover the optimal arrangement for three control variables.

Problems during the Design and Testing of Instrument, Special and Power Transformers: The Outlook

In 1831, Michael Faraday discovered the phenomenon of electromagnetic induction, which allowed for the construction of previously unknown electrical devices and significantly impacted economic and social development [...]

Research on Magnetic Characteristics and Short-Circuit Force of 3D Wound Core Transformer

The problem of eddy current loss in power transformers directly affects the technical economy of the transformer, which is a problem that cannot be ignored in the design and calculation of power transformers. Studying how to reduce the eddy current losses caused by leakage magnetic fields is a difficult point in transformer design. The load loss of low-voltage foil copper windings in a 10 kV/400 kVA 3D wound core transformer is calculated, and the three-dimensional finite element models of the transformer are established by Using Magnet software and COMSOL Multiphysics software, and the calculation results are compared. At the same time, the short-circuit force of foil windings is shown in the simulation. The results show that the three-dimensional finite element models are correct.

Power Transformer Characterization and Design Optimization Environment

Power Transformers are essential part of all AC Power Grids. This work proposes a characterization and design optimization environment for Power Transformers to increase efficiency while decreasing core volume. It utilizes a Finite-Element State-Space models in conjunction with Artificial Neural Networks and Particle Swarm Optimization. A case study of a 42 MVA, 118/13.8kV distribution power transformer was conducted, and transformer performance characteristics were compared to test data for verification. Next, the optimization environment was used to decrease the transformer volume and improve its efficiency. In addition, the Taguchi orthogonal arrays method was used to reduce computational costs.

On the Feasibility of Monitoring Power Transformer's Winding Vibration and Temperature along with Moisture in Oil Using Optical Sensors.

Despite major progress in the design of power transformers, the Achilles' heel remains the insulation system, which is affected by various parameters including moisture, heat, and vibrations. These important machines require extreme reliability to guarantee electricity distribution to end users. In this contribution, a fiber optic sensor (FOS), consisting of a Fabry-Perot cavity made up of two identical fiber Bragg gratings (FBGs), is proposed, to monitor the temperature and vibration of power transformer windings. A phase shifted gratings recoated sensor, with multilayers of polyimide films, is used to monitor the moisture content in oil. The feasibility is investigated using an experimental laboratory transformer model, especially fabricated for this application. The moisture contents are well correlated with those measured by a Karl Fisher titrator, while the values of temperature compare well with those recorded from thermocouples. It is also shown that the sensors can be used to concurrently detect vibration, as assessed by sensitivity to the loading current. The possibility of dynamically measuring humidity, vibrations, and temperatures right next to the winding, appears to be a new insight that was previously unavailable. This approach, with its triple ability, can help to reduce the required number of sensors and therefore simplify the wiring layout.

Effect of ferromagnetic paste on insulating properties of transformer oil

THE PURPOSE. Consider the problem of using a special ferromagnetic paste, which fills the air gaps in the magnetic circuit of an oil power transformer, in order to reduce its losses, by reducing eddy currents in the magnetic circuit. Conduct experiments to determine the dynamics of change of high-voltage breakdown of transformer oil, after adding ferromagnetic paste to it.METHODS. To solve this problem, several samples of ferromagnetic paste have been developed, differing from each other using different binding material for ferromagnetic powder. The samples were placed in containers for several days filled with transformer oil. With the help of electrical installation AIM-90, measurements of high-voltage breakdown of transformer oil of each sample were carried out. Thanks to this method, it was possible to determine how the ferromagnetic paste affects the insulating properties of the transformer oil. RESULTS. For clarity, the results of all samples were plotted. Based on the graph, it became clear that in some samples of transformer oil a significant amount of mechanical impurities formed from ferromagnetic paste appeared, which extremely negatively affected the insulating properties of the oil. There were also samples in which the properties of the oil practically did not change. CONCLUSION. As conclusions, there was a certain vision of which ferromagnetic paste can be used in the design of an oil power transformer, it was also possible to understand which samples of ferromagnetic pastes extremely negatively affect the insulating properties of the transformer oil.

A Case Study for 50 kVA Toroidal Core Partially Superconducting Transformer

We report some numerical results obtained for 50kVA single phase partially superconducting toroidal and core power transformers. Transformers are calculated using the Comsol Multiphysics software with ac/dc and heat transfer modules. They are modeled in such a way that their primary parts (medium voltage) consist of copper windings and secondary parts (low voltage) are formed by superconducting MgB2 windings which are immersed into the liquid helium. Magnetic flux density profile on the iron core, primary and secondary currents, transformer power, and AC losses in superconducting windings are explored for one full cycle of AC voltage. Short-term temperature investigation for quenching showed that AC losses act as a heat source. We think that these numerical results are very important in terms of industrial-scale superconducting transformer applications because there are very few studies on MgB2 transformers. Our results will enable the design of toroidal-type power transformers that may be operable in practice. According to the numerical simulation results, it seems that a compact low cost superconducting MgB2 toroidal transformer can be realized with advances in cryostat systems and reducing AC losses. We suggest that the present study will contribute to the literature according to both the models applied and the results obtained.

"Power Transformer Design Optimization and Productivity Evaluation Using Artificial Intelligence Techniques"

Transformers need to be designed in a way that satisfies not only all international requirements and customer expectations but also that they are effective, economically practical, and satisfy all international criteria. The design of a transformer should ultimately achieve this goal. It is anticipated that the costs of active components, development, and ownership will decrease as the application of AI approaches becomes more widespread. This is expected to occur while maintaining compliance with international standards and constraints. Using the AI technologies that are currently being utilized in Indian manufacturing will not be sufficient to solve TDO issues. The current research is focusing on developing artificial intelligence-based solutions that have the potential to be used to improve the design of distribution transformers. By utilizing this design for the transformer, both the total ownership costs and the expenses associated with its manufacture would be cut in half (TOC). It was demonstrated that when attempting to solve TDO problems using techniques such as GA, PSO, and TLBO, PSO and GA found higher objective feature values than GA. When it comes to percentages, TLBO performs significantly better than both PSO and GA. As a result of the implementation of NSGA II, the TOPSIS technology made it possible for DM to select any solution from among the non-dominated solutions

Eco-Friendly Ester Fluid for Power Transformers versus Mineral Oil: Design Considerations

Mineral oil has long been used as an adequate coolant and dielectric medium in power transformer design. However, it is flammable and environmentally risky as it may be leaked or spilled. Therefore, ester fluids, which have been increasingly used in the last two decades, look promising as an ideal dielectric option. This research aims to better understand how using ester fluid insulation in power transformers impacts their physical and electrical dimensions, including their load-losses, impedance, masses, and equipment dimensions. Three case studies were carried out in a Portuguese electrical equipment manufacturer’s facility, with varying electrical parameters and physical properties of the mineral oil and ester-filled power transformers. The main results enhanced the known good electrical behavior of ester fluids, namely creating a lower electric field around winding wedges, yet the use of ester fluids led to higher load-losses, larger masses, additional radiators and, consequently, higher manufacturing costs. Nevertheless, the contribution of ester-filled power transformers to the improved environmental safety (reducing spillage and fire risks), among other advantages, makes ester fluids a truly eco-friendly option for power transformer design.

Simulation of reactance of built-in reactor in power transformer with field-circuit coupling method

Using low-voltage winding series built-in reactor in power transformer was one of the effective methods to improve the impedance of transformer. It was useful and benefit for the impedance selection and design of power transformer by researching on the simulation calculation of leakage reactance under the normal operation and short-circuit fault condition of transformer with built-in reactor. In this paper, a finite element model was established based on the structural parameters of an actual power transformer with built-in reactor. The leakage magnetic field and leakage inductance parameters of the teansformer with built-in reactor under the normal operation and short-circuit condition were calculated respectively using “Magnetic-Circuit” coupling method, and the changes of leakage reactance were compared.The results show that, when the transformer was short-circuit, the short circuit current will passing through built-in reactor, which would cause the core framesaturated, and the leakage reactance of the built-in reactor would be reduced. The research results shown that the problem of leakage reactance reduction of built-in reactor should be considered in the design of short-circuit resistance of transformer, which was of great significance to guide the short-circuit design of power transformer.

Dielectric Design of Ester-Filled Power Transformers: AC Stress Analysis

In the last 20 years the use of ester fluids as an alternative to mineral oil for transformer insulation has been an active field of research and development. These liquids have a much lower environmental impact than mineral oils, besides reducing the transformer’s fire risk. Although the use of natural and synthetic esters is nowadays frequent for certain applications, as for distribution transformers in highly populated areas, railway transformers or off-shore windmill transformers, the experience on large and medium sized units is still reduced. One of the critical aspects that must be assessed to use esters as dielectric fluids for large size transformers is the dielectric design of the equipment. The permittivity of esters and ester-impregnated cellulose are different from those of mineral-oil-cellulose systems, what has an impact on the electric field distribution in the transformer. Additionally, in some cases, the dielectric strength of ester fluids differs from that of mineral oil. This paper presents a study about the dielectric design of ester-based power transformers. The insulation system of a 400/138 kV, 280 MVA transformer was modelled using a finite element tool and a comparison of the field distribution under 50 Hz AC power voltage of both insulation systems is provided.

Application of Energy Saving Technology in Power Transformer Design

Application of Energy Saving Technology in Power Transformer Design

Analysis and Design of a Special Type Power Transformer Used in Solar Power Plants

Analysis and Design of a Special Type Power Transformer Used in Solar Power Plants

A VR-Enabled Chatbot Supporting Design and Manufacturing of Large and Complex Power Transformers

Virtual reality (VR) immersive technology allows users to experience enhanced reality using human–computer interfaces (HCI). Many systems have implemented VR with improved HCI to provide strategic market advantages for industry and engineering applications. An intelligent chatbot is a conversational system capable of natural language communication allowing users to ask questions and receive answers online to enhance customer services. This research develops and implements a system framework for a VR-enabled large industrial power transformer mass-customization chatbot. The research collected 1272 frequently asked questions (FAQs) from a power transformer manufacturers’ knowledge base that is used for question matching and answer retrieval. More than 1.2 million Wikipedia engineering pages were used to train a word-embedding model for natural language understanding of question intent. The complex engineering questions and answers are integrated with an immersive VR computer human interface. The system enables users to ask questions and receive explicit and detailed answers combined with 3D immersive images of industrial sized power transformer assemblies. The user interfaces can be projected into the VR headwear or computer screen and manipulated with a controller. The unique immersive VR consultation chatbot system is to support real-time design consultation for the design and manufacturing of complex power transformers.

Physical modeling of unsteady electromagnetic processes in power transformer under sharp load fluctuations

Purpose. To develop and experimentally confirm the method of physical modeling of non-stationary electromagnetic processes in a powerful power transformer operating under variable loads by combining similarity criteria and equivalence coefficients. Methodology. Theoretical provisions of mathematical and computer modeling, theoretical electrical engineering were used in the research, as well as the theory of experiment with the application of equivalence coefficients. Findings. Methods of experimental research were developed, which include the formation and registration of a set of external and internal parameters of physical models, prototypes and real equipment. Criteria for similarity of nonstationary electromagnetic processes excited by sharply changing scattering fields in special purpose power transformers are obtained. . Originality. The theory and practice of physical modeling, as well as the similarity theory applied to unsteady electromagnetic processes in powerful transformer equipment for special purposes were further developed. A set of distinctive features of test conditions and their registration were formed. Practical value. Application of physical modeling of unsteady electromagnetic processes at the design and manufacture stages of power transformers for power supply systems of electric arc furnaces, rolling mill drives, etc., as well as during the refinement of general-purpose power transformers.

Development of model of transient modes taking into account mutual inductance of scattering fields for implementation of digital twin of transformer

Development of the refined mathematical models of power transformers (digital twins), which make it possible to calculate arbitrary modes of operation of these devices with high accuracy and increased speed is an urgent task. Currently, such problems are solved using simulation packages such as MatLab Simulink. One of the disadvantages of the existing simulation models of the transformer is the assumption that own leakage inductance of the windings is used. This assumption is not always acceptable. Thus, the purpose of this article is to develop models of transformers using matrices of mutual inductance of the scattering field. The finite element method is used to calculate the magnetic field in a 2D formulation, implemented by means of the EMLib library, as well as simulation methods with the MatLab Simulink package are applied. The authors have estimated the features and basic assumptions while developing refined mathematical models of power transformers of various designs (two- and three-winding). It makes possible to ensure the required accuracy when simulating transient and emergency modes of transformer operation. Field models have been developed to determine the own and mutual scattering inductance matrices. Simulation models of transformers of various designs with the use of winding leakage inductance matrices have been developed. The results of simulation of dynamic processes in a transformer in various modes are presented. Comparison of the results of the operation of models with matrices of mutual inductances and without them is carried out. The results of the research can be used during the design of power transformers in design companies and in production environment. It is also possible to use the developed models during operation of power transformers for the analysis of static and dynamic modes of operation of sections of electrical networks.

Fast Hybrid Approach for Calculation of Losses in Outer Packages of Transformer Core Due to Perpendicular Stray Flux

Stray flux in a transformer enters the outer packages of a core perpendicularly and induces significant eddy currents that cause ohmic losses. Local thermal conditions near the core are affected by these losses that are dissipated as heat and can cause local overheating in the oil near the outer packages. Stray losses in the outer packages should be considered during the power transformer design process, and it is, therefore, important to model them properly. This type of loss can be solved using 3-D FEM; however, that approach is time-consuming, which makes it impractical for the loss calculation in real time. Another approach is 2-D modeling, which is faster, but it is limited to axisymmetric and planar geometries only. Due to its complex geometry, a transformer cannot be modeled using a single 2-D model. Instead, each quantity of interest, such as a magnetic field or eddy currents, can be obtained from a suitable model. These models include certain simplifications, which should not affect the accuracy of the results. In this article, a hybrid approach that utilizes various 2-D models for the calculation of stray losses in the outer packages is proposed. The advantage of the proposed methodology is in obtaining the same level of accuracy while considerably reducing the calculation time when comparing to the 3-D FEM approach. The estimation of the temperature rise of the outer packages, based on the calculated losses, will be a part of further research.

Vibration characteristics and vibration isolation design of oil-immersed power transformer

Transformer vibration and noise has become a prominent problem in power grid construction and operation. Firstly, on the basis of expounding the vibration mechanism of iron core and winding, the transmission path of vibration and noise of transformer is analyzed. Secondly, it is pointed out that it is not cost-effective to control transformer vibration and noise only from the selection of core and winding materials, manufacturing process and structural optimization. It is necessary to start from the transmission path of transformer sound and vibration, and adopt auxiliary vibration reduction and noise reduction measures such as vibration isolation of the body to reduce the transmission of vibration of the body to the oil tank wall, foundation and adjacent structures. Then, the design method of oil immersed power transformer body vibration isolation is discussed, and the relevant parameters such as frequency ratio, damping ratio and the arrangement of vibration isolation support are proposed. The reasonable vibration isolation design of transformer body can achieve remarkable vibration isolation effect and the vibration isolation efficiency can reach more than 96%. Finally, the vertical design stiffness of 81 kinds of oil immersed power transformer vibration isolation layers with 4 voltage levels of 10 kV, 35 kV, 110 kV and 220 kV are calculated. Taking a typical 110 kV transformer as an example, the corresponding vibration isolation design scheme is proposed. The research provides a good reference for the vibration isolation design of transformer body in the future.