Magneto-Thermo-Structural Analysis of Power Transformers under Inrush and Short Circuit Conditions (original) (raw)
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This work presents a study regarding the contribution of inrush current to the occurrence of mechanical fatigue in windings of a power transformer and, consequently, the impact of that phenomenon on the equipment's lifetime. In order to perform the study, electromagnetic transient simulations were used to determine the inrush current in a three-phase transformer model. Then, three-dimensional simulations, based on the finite element method, were performed to determine the electromechanical stresses in the equipment windings, under the effect of the inrush current. Next, the methods of critical plans and Palmgren-Miner were applied to perform the fatigue study. From the results, the impact of inrush current on the integrity of the transformer's windings was determined, as well as, to estimate the reduction of lifespan of the equipment due to inrush occurrence. The number of inrushes needed for the total reduction of lifespan of the equipment due to mechanical fatigue was also determined. The results can be used in the transformers design stage, with the purpose of assisting the evaluation of mechanical withstand of equipment, which can minimise the possibility of failure and increase its lifespan.
Analysis of Structural Behavior of Transformer's Winding Under Inrush Current Conditions
IEEE Transactions on Industry Applications, 2018
The objective of this paper is to investigate the behavior of electromagnetic forces during the occurrence of faults inside transformers as result of transients in the electrical systems. The methodology is based on modeling of a single-phase 50 MVA transformer subjected to inrush currents through Finite Element Method (FEM). In this perspective, the values of inrush currents, obtained by the Alternative Transient Program (ATP) software, are used to estimate the magnetic field density dispersion in the transformer and to find the values of forces in axial and radial directions. These forces components are distributed along the energized windings for observing the loads behavior in high-voltage windings. This paper will thus present investigations of electromagnetic forces, structural deformation, stresses, and safety factor on transformer's winding when subjected to inrush current.
International Journal of Emerging Electric Power Systems, 2008
The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification.Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost ...
Power transformer under short-circuit fault conditions: A multiphysics approach
Transformers Magazine, 2020
Transformers' windings experience mechanical loads from electromagnetic forces due to the currents they carry. During normal operation, the resulting stresses and strains have minor influence, therefore they do not represent the significant risk to the devices' integrity. However, transformers can suffer from high sudden short-circuit currents that are several times higher than those during the normal operation. These short-circuit currents are a significant threat, not only from an electrical but also from the structural integrity point of view. In this paper, coupled electromagnetic and structural mechanics simulations are carried out to evaluate short-circuit fault risks in a comprehensive and accurate way.
Modeling of Magnetizing Inrush and Internal Faults for Three-phase Transformers
Indonesian Journal of Electrical Engineering and Computer Science, 2016
Among the most noticeable root causes of improper performance in power transformers, internal short circuit faults can be noted and if not quickly be identified and addressed in the accepted time interval, irrecoverable damages such as interruption or even collapse of the network connected to the power transformer would happen. In this contribution, three-phase transformer behaviors under magnetizing inrush, internal short circuit condition and their current values determination have been surveyed using electromagnetic coupling model approach and structural finite element method. Utilizing the definition of transformer in the form of multi-coil and their electromagnetic and electric couple, a three dimensional geometric model of transformer is developed which includes nonlinear characteristics of the transformer, different states of normal and under internal short circuit occurrence and the moment of magnetizing inrush creation are investigated. The comparison between obtained resul...
International Journal of Applied Electromagnetics and Mechanics, 2016
The main objective of this paper is to assist in the investigation of electromagnetic forces, structural deformation, stresses, and Safety factor when energizing unloaded transformers. The methodology is based on modeling of a single-phase 50 MVA transformer subjected to inrush currents through finite element method (FEM). In this perspective, the conditions of inrush currents are used to estimate the magnetic field density dispersion in the transformer and to find the values of forces in axial and radial directions. These components are distributed along the energized windings for observing the loads in highvoltage windings. Thus, this article will contributes with the investigations of a structural Analysis on transformers when subjected to inrush current.
Performance Evaluation of a Transformer Using Finite Element Method
Master of Engineering Thesis GTU India, 2013
Transformers are most essential and consequential elements in electricity transmission and distribution. Therefore, in order to have a transformer working at optimum level, many researches and tests have been being performed. The goal of these tests and researches is reducing the amount of losses and extends lifetime of a transformer. During the conversion of the electricity in a transformer, some losses occur. These losses occur at windings and core of the transformer and they turn into heat. Transformers are widely used in almost all industrial application and is must for any basic industrial setup. As every machine, when running under normal condition is subjected to different kind of faults, the solution of which has to be carried out in advance to achieve best possible efficiency before actual use of the transformer. In the initial step, we go through the numerous papers which has worked on different parameters of transformer using FEM analysis. And the results of the same will be used in determining modelling of a transformer in the software using Finite Element approach. This method helps to develop accurate models of the machine under both healthy and faulty conditions. It also accurately calculates magnetic fields and related transformer design parameters for different types of transformers with completed geometry, which increases possibilities of improving the design during the planning stage (Before actual use of transformer). Using this method, analysis of Internal Insulation Design Improvements, Accurate Prediction and Minimization of No Load Loss, Internal Stresses at high frequency and faults like leakage reactance, internal winding stress etc. will be carried out. The analysis with the fault condition listed above will be simulated in FEM based software and the result will be compared with that of the transformer under healthy condition, which helps a great in knowing the worst possible condition under which transformer can be used. The design of the transformer carried out by the above method will be helpful to the industry in the sense that maximum possible efficiency and accurate calculation of magnetic field and stresses on windings can be achieved under worst possible conditions.
Electromagnetic Forces in Power Transformers under short circuit conditions
Zenodo (CERN European Organization for Nuclear Research), 2022
Power transformers are among the most expensive and key apparatuses in an electric power system. It is important thus, that they are properly protected and well-maintained. Transformers experience different stresses while in operation. The effect of electromagnetic force on transformer windings is worsened by electrical, mechanical, and thermal issues. Damage from the increase in electromagnetic force includes winding displacement, bending, and tearing. Therefore, it is essential to predict electromagnetic force when designing transformers. This paper investigated the causes and process of damage to transformer windings due to electromagnetic forces when these windings are short-circuited and recommended mitigation measures for the safer and more reliable operation of power transformers under such conditions.
IEEE Transactions on Magnetics, 2000
Although short-circuit current is frequently considered the major design fundamental for power transformers, experience with transformer failures shows that inrush currents that occur when transformers are energized can also cause serious damage. To investigate the resultant forces due to energizing power transformer windings, we modeled a three-phase, three-legged 66/11 kV, 40 MVA power transformer in two and three dimensions. We calculated electromechanical forces for short-circuit cases and also for inrush current through the windings, using the finite-element method. The results show that the forces exerted on the windings due to inrush current in many regions are larger than those due to short-circuit currents. Since the inrush current appears more frequently with a much longer duration compared to a short-current event, its harmful effects are worse than those of the short-circuit case.