Thermal modeling of disc-type winding for ventilated dry-type transformers (original) (raw)
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Temperature distribution in foil winding for ventilated dry-type power transformers
Electric Power Systems Research, 2010
Predicting temperatures of transformers is important in order to prevent the deterioration of electrical insulation since the life of the transformers corresponds with that of the insulation. Reports of thermal behavior of ventilated dry-type transformers are rare in the literature. In particular, foil winding has received little attention despite their wide usage in practice. In this study, a thermal model for foil winding was proposed and temperature distributions were determined by the finite element method (FEM). In order to cope with the non-uniformity of the heat fluxes in the foil winding due to induced currents, different convection coefficients and varying air temperature along the vertical height of the foil winding were suggested and applied to the thermal model. The thermal model was solved by coupling it with the electromagnetic model to calculate the non-uniform power losses. The model was applied to a ventilated dry-type power transformer rated at 2000 kVA. Experimental temperatures were measured with thermocouples, and used to verify the finite element results. They showed reasonable agreement and will provide a useful tool for transformer engineers.
Winding Hottest-Spot Temperature Analysis in Dry-Type Transformer Using Numerical Simulation
Energies, 2018
A thermal analysis of a 5 kVA dry-type transformer under linear and non-linear loads conditions is studied in this paper. The main goal here is to calculate the hottest-spot transformer temperature under free convection through the resolution of the heat conduction equation in three dimensions (3D) using COMSOL Multiphysics®. The proposed technique was validated through experimental data obtained in laboratory. The temperature inside the cores was measured under the influence of free convection. The radiation emission was also measured through a thermal camera. The heat transfer coefficient for both conditions was obtained from empirical correlations. The hottest-spot temperatures were determined from the analysis in the commercial software which was used for the numerical simulations of the transformer heating and cooling under some loading conditions. The temperature residuals, that is, the experimental temperature values subtracted by the numerical temperature values, were below ...
Temperature Distribution in The Disc-Type Coil of Transformer Winding
Second International Conference …, 2001
In this study a series of numerical experiments are conducted so as to develop a new thermal model for oilimmersed transformer windings. A line of eight-disc-coil has been modelled as a series of heat producing sources in a vertical channel. The heat transfer equations for the model in hand were solved by a semi numerical-analytical method to obtain temperature distribution. Also, the results obtained are verified by ANSYS packet program. And the results obtained are in good enough agreement with open literature.
Dry-Type Power Transformers Thermal Analysis with Finite Element Method
The transformer temperature is one of the main variables of interest in its manufacture and operation, since it interferes in the useful life of the transformer. In this sense, the present work proposes a thermal simulation for the temperature estimate of a dry-type transformer. Initially a thermal analysis was performed from experimental measurements of temperatures of a dry-type power transformer of 500kVA for different conditions of load. Posteriorly, a thermal simulation was proposed using finite element theory. Thus, the heat diffusion equation was used, with the following boundary conditions: convection and radiation equations; characteristics of the materials used; the measurement data and the dimensions of the transformer. FEMM 2D software was used for the proposed simulation. Finally, in order to validate the proposed analyzes, experimental measurements were compared with the values obtained in the thermal simulation. The results of the thermal simulation showed agreement with the experimentally measured values.
Different Approach to Thermal Modeling of Transformers-a comparison of methods
2011
This paper presents a thermal models to simulate a thermal behaviour of different type of transformers. Heat disipated is always problem in transformers, esspecialy in large power transformers. Coupled physical and mathematical models would assist in the development of a system that was both accurate and simple to implement. Material proporties, the geometry of the model, heat transfer coefficients for each surfaces are introduced as the input values. For the accurate results of the temperature distributions, the exact values of heat transfer coefficients are required. However this can be managed by solving the flow field equation by using any means, i.e. numerical methods, analytical methods. The performances of the models are compared to the analytically determined performance of transformer or to the experimentally determined performance of transformer and the results obtained are in a good enough agreement with open literature. The thermal models based on finite element analysis...
A New Thermal Modeling of Dry Type Transformers and Estimating Temperature Rise
2013
A power transformer is a static piece of apparatus with two or more windings, which by electromagnetic induction transforms a system of alternating voltage and current into another system of voltage and current, usually of different values and at the same frequency for transmitting electrical power. Temperature rise is one of the most crucial parameters that affect the transformer lifetime. Temperature rise in a transformer depends on variety of parameters such as ambient temperature, output current and type of the core. Considering these parameters, temperature rise estimation is still complicated procedure. In this paper, we present a new model based on temperature rise. This method avoids the complication associated to accurate estimation and is in very good agreement with
Thermal Modelling of Electrical Insulation System in Power Transformers
Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment, 2018
Temperature is one of the limiting factors in the application of power transformers. According to IEC 60076-7 standard, a temperature increase of 6 C doubles the insulation ageing rate, reducing the expected lifetime of the device. Power losses of the transformer behave as a heating source, and the insulating liquids act as a coolant circulating through the windings and dissipating heat. For these reasons, thermal modelling becomes an important fact of transformer design, and both manufacturers and utilities consider it. Different techniques for thermal modelling have been developed and used for determining the hot-spot temperature, which is the highest temperature in the winding, and it is related with the degradation rate of the solid insulation. First models were developed as a first estimation for modelling the hot-spot temperature and the top-oil temperature. These models were based on thermal-electric analogy and are known as dynamic models. Other two different kinds of models are widely used for thermal modelling, known as Computational Fluid Dynamics (CFD) and Thermal Hydraulic Network Models (THNMs). These two techniques determine the temperature and velocity fields in the winding and in the insulating fluid. In this chapter, the different techniques for transformer thermal modelling will be introduced and described.
Thermal modeling of electrical utility transformer
2009 International Conference on Power Systems, 2009
Heat dissipation is always a problem in large power transformers. Increased market competency demands for accurate determination of the thermal profile across the transformer. This paper presents a thermal model to simulate the thermal behavior of the electrical utility transformers. The thermal model is arrived at using the principle of thermal electrical analogy and the fact that the losses in the transformer are distributed rather than lumped. In this paper, the model is implemented for single phase transformer and the same model can be extended to three phase transformer. Simulation results are presented.
Power Transformer Winding Thermal Analysis Considering Load Conditions and Type of Oil
Power transformer outages have a considerable economic impact on the operation of an electrical network. In order to draw maximum power from transformers and, at the same time, avoid thermal mishaps, it is essential to carefully study its thermal behavior. Furthermore, an accurate computation of the hottest spot temperature (HST) helps in a realistic estimation of the reliability and remaining life of the transformer winding insulation. This paper presents steady state temperature distribution of a power transformer layer-type winding using conjugated heat transfer analysis, therefore energy and Navier-Stokes equations are solved using finite difference method. Meanwhile, the effects of load conditions and type of oil are investigated using the model. Oil in the transformer is assumed nearly incompressible and oil parameters such as thermal conductivity, special heat, viscosity, and density vary with temperature. Comparing the results with those obtained from finite integral transform checks the validity and accuracy of the proposed method.
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 ...