Distribution Transformer Loss Research Articles

Separation of core losses in distribution transformers using experimental methods

The separation of eddy current and hysteresis losses in transformer cores is obtained using the two-temperatures and the two-frequency methods. Loss calculations for six ratings using the voltage test waveform ratio are included to compare and analyze results. A brief description of the test methodologies, that are easy to apply, is given. An example of the application of the methodologies, the obtained measurements and obtained results are included. In some cases, the results show that eddy current losses for the analyzed ratings are greater than 60% of no-load losses. Results include the impact of no-load losses in total owning cost of transformers.

Harmonic Impact on Distribution Transformer No-Load Loss

The losses in European Union distribution transformers are estimated at about 33 TW ·h/year, whereas reactive power and harmonic losses add a further 5 TW ·h/year. The reduction of distribution transformer no-load loss is particularly important as the ratio of no-load to load losses is nearly three. In this paper, the no-load operation of wound-core transformers under sinusoidal and distorted supply-voltage conditions is investigated. For that purpose, a 2-D nonlinear transient finite-element analysis taking into account hysteresis has been developed. The hysteresis model is based on a modified Jiles-Atherton representation, and the proposed analysis is compared to experimental data.

A Preliminary Assessment of the Impact of Ambient Temperature Rise on Distribution Transformer Loss of Life

Although there are still uncertainties regarding the extent to which climate change may be occurring, some approximations and reasonable assumptions can be made relating to daily high and low temperatures. Further, urbanization may impact ambient temperature. These temperature models may be used with standardized methods to estimate the loss of life of oil-immersed power distribution transformers. In this way, the impact of increased ambient temperatures on distribution transformer loss of life may be preliminarily assessed. Results of standardized engineering studies for illustrative cases are shown in this paper.

Transformers of reduced losses and evaluation of their repair

The purpose of this work is to determine the optimum reduction of iron and copper losses in distribution transformers. Design and life-cost calculations for transformers 20 kV/400 V of a nominal power 50–1000 kVA were performed, for estimating the final transformer price for different amounts of loss reduction, in order to find out the minimum annual operational cost of these transformers. For estimating the annual cost, the final transformer price and the power and energy cost due to the transformer losses have been used. In this way, the optimal losses (iron + copper) have been found out for the minimum annual cost. The impact of a damaged tranformer's age on the economic decision for its repair has been investigated as well.

Closure on "reducing losses in distribution transformers"

The authors reply to the comments made separately by X. Dong (see ibid., vol.18, no.4, p.1593, 2003) and S.V. Kulkarni (see ibid., vol.18, no.4, p1593-4, 2003) on their original paper (see ibid., vol.18, p.821-6, 2003). For Dong they offer remarks regarding economical analysis of their application and the formulas of stray losses for distribution transformers. For Kulkarni they answer each of his five questions regarding the losses.

Discussion of "Reducing losses in distribution transformers"

The author comments on the paper by J.C. Olivares et al. (see ibid., vol.18, p.821-6, 2003) suggesting that the authors investigate the economic analysis of the application of magnetic shielding, and that they obtain formulas considering magnetic shielding relating to stray loss and load loss.

Discussion of "Reducing losses in distribution transformers

The author comments on the paper by J.C. Olivares et al. (see ibid., vol.18, p.821-6, 2003) asking for clarification on five points relating to the losses.

Reducing losses in distribution transformers

This paper examines three methods of reducing distribution transformer losses. The first method analyzes the effects of using aluminum electromagnetic shields in a distribution transformer. The goal of placing electromagnetic shields in the distribution-transformer tank walls is to reduce the stray losses. A 500 kVA shell-type transformer was used in the experiments. The overall results presented indicate that stray losses can be considerably reduced when electromagnetic shielding is applied in the transformer tank. In the experiment, the tank walls were lined with aluminum foil. The possibility of reducing the dielectric losses was shown through experiments in the second method. The third method of this work analyzes the behavior of wound-cores losses in distribution transformers, as a function of joint configuration design parameters. The joint configuration used in this paper is called step-lap joint.

The transformer thermal loss of life: Part 1 ‐ improved deterministic approach for thermal and ageing models

AbstractDue to computers' widespread, models used in Power Engineering reached an unthinkable complexity and precision. However, the nature of the problem has changed: we rarely use fully the precision of nowadays models, because parameters and operating conditions are submitted to uncertainty. Apart from a limiting range of rated values, realistic operating conditions are not completely known, which is as evident as long the device is alife. In this context, the estimation of the distribution transformer loss of life is a pertinent problem that we propose to solve by developing and illustrating a new appropriate methodology. Because of the subject extent, we considered three successive aspects: first, an improved deterministic approach for thermal and ageing models; second, a probabilistic extension considering functional variability and model structural uncertainty and the third one, an application to the power derating problem in case of harmonic distortion load. This paper corresponds to the first aspect.

Reducing Losses in Distribution Transformers

This paper examines three methods of reducing distribution transformer losses. The first method analyzes the effects of using aluminum electromagnetic shields in a distribution transformer. The goal of placing electromagnetic shields in the distribution-transformer tank walls is to reduce the stray losses. A 500 kVA shell-type transformer was used in the experiments. The overall results presented indicate that stray losses can be considerably reduced when electromagnetic shielding is applied in the transformer tank. In the experiment, the tank walls were lined with aluminum foil. The possibility of reducing the dielectric losses was shown through experiments in the second method. The third method analyzes the behavior of wound-cores losses in distribution transformers as a function of joint configuration design parameters. The joint configuration used in this paper is called step-lap joint.

A novel iron loss reduction technique for distribution transformers based on a combined genetic algorithm - neural network approach

The paper presents an effective method to reduce the iron losses of wound core distribution transformers based on a combined neural network/genetic algorithm approach. The originality of the work presented is that it tackles the iron loss reduction problem during the transformer production phase, while previous works concentrated on the design phase. More specifically, neural networks effectively use measurements taken at the first stages of core construction in order to predict the iron losses of the assembled transformers, while genetic algorithms are used to improve the grouping process of the individual cores by reducing iron losses of assembled transformers. The proposed method has been tested on a transformer manufacturing industry. The results demonstrate the feasibility and practicality of this approach. Significant reduction of transformer iron losses is observed in comparison to the current practice leading to important economic savings for the transformer manufacturer.

Effective use of magnetic materials in transformer manufacturing

This paper has a twofold objective: (a) optimizing the production process of individual cores using Taguchi methods, and (b) reducing the iron losses of assembled transformers, using neural networks. More specifically, we demonstrate the ability of the Taguchi technique accurately to characterize and successfully to optimize the transformer core production process with the minimum of experiments. Moreover, neural networks have been applied to predict iron losses of wound core distribution transformers at the early stages of core construction. The intelligent iron loss model is on-line applied in order to optimally combine the individual cores so that the iron losses of assembled transformers is reduced.

Distribution transformer loss of life evaluation: a novel approach based on daily load profiles

This work presents a methodology for distribution transformer rating selection and management. Measured or estimated daily load profiles are used to determine the transformer's loss of life. Loss of life values are obtained for a number of transformers and are stored together with the corresponding load profiles in a database of patterns. The expected loss of life for a transformer not included in the database is obtained by comparing the transformer's actual load profile to the ones stored in the database.

Prediction of iron losses of wound core distribution transformers based on artificial neural networks

This paper presents an artificial neural network (ANN) approach to predicting and classifying distribution transformer specific iron losses, i.e., losses per weight unit. The ANN is trained to learn the relationship of several parameters affecting iron losses. For this reason, the ANN learning and testing sets are formed using actual industrial measurements, obtained from previous completed transformer constructions. Data comprise grain oriented steel electrical characteristics, cores constructional parameters, quality control measurements of cores production line and transformers assembly line measurements. It is shown that an average absolute error of 2.32% has been achieved in the prediction of individual core specific iron losses and an error of 2.2% in case of transformer specific losses. This is compared with average errors of 5.7% and 4.0% in prediction of specific iron losses of individual core and transformer, respectively, obtained by the current practice applying the typical loss curve to the same data.

Modeling of iron-loss components of grain-oriented silicon steel for accurate calculation of core losses of power and distribution transformers

Accurate estimation of iron-loss components of grain oriented silicon steel plays an important role in accurately predicting the core loss performance of power and distribution transformers. Existing practice among design engineers is to approximate the material iron loss performance by a simple curve-fit, like a polynomial, This paper presents the development of an improved analytical model which consists of terms that explicitly represent loss components contributing to the total iron loss of the transformer core material. These are expressed in terms of the operating flux density, frequency, and lamination thickness. Not only is the developed model simple and practical, but it also provides transformer design engineers with accurate understanding of the behavior of each loss component. The results presented here demonstrate the excellent accuracy resulted from using the model in calculating the transformer core loss performance at the design stage.

Calculation of spatial loss distribution in stacked power and distribution transformer cores

This paper describes an analytical solution to use a generic 2D finite difference method to accurately calculate the quasi 3D spatial distribution, components, and total core losses in transformer cores. The solution takes into account: (1) magnetic anisotropy and nonlinearity of the core material; (2) all components of iron losses of the core material, including losses in directions other than the rolling direction; and (3) joint model and localized losses due to the distorted flux distribution in the joint regions (due to core gaps) across the core-stack. The results are used to: (1) calculate very accurately the total core losses of a transformer at the design stage every time, for all core materials, at all operating inductions, for all core geometries, for both 50 Hz and 60 Hz; (2) understand the contribution of cross losses, harmonics, and joints to the total losses of a core; (3) evaluate the impact of various joint attributes, such as, type of joint, number of steps, number of laminations per step, size of gaps, and lamination thickness on the total performance of the core; and (4) improve the core loss performance of transformers by optimizing core design and core material parameters. This paper presents the analysis as applied to 3-phase, 3-limb cores. The paper also presents the results of the extensive experimental/test verification performed on a number of model cores in the lab as well as on a large number of actual commercial transformer cores with excellent agreements. The results have been used to calculate core losses of stacked power and distribution transformers with consistent accuracy.

Case study of radial overhead feeder performance at 12.5 and 34.5 kV

The electric performance and the economics of four supply options for a specific 12.5 kV radial distribution feeder were examined. Options included upgrading to 34.5 kV and/or sectionalizing. Feeder losses, voltage regulation, and system voltage dips due to feeder faults were analyzed. It was found that distribution transformer losses were a significant component in the total feeder loss and an important factor in the loss comparison of the two voltage levels. In this case, sectionalizing the existing feeder at 12.5 kV was the preferred option based upon cost, system voltage dip performance, and ease of back feed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Cost of Load Losses in Distribution Transformers by the Method of Average Loading

Cost of Load Losses in Distribution Transformers by the Method of Average Loading

Cost of Load Losses in Distribution Transformers by the Method of Average Loading

The cost of load losses for distribution transformers may be solved by using the average loading on the transformer. The main calculation is the division of the system-wide average load on distribution transformers by the connected MVA of distribution transformers. This method provides for simple calculations with a minimal amount of data.

Distribution Transformer Winding Losses Due to Nonsinusoidal Currents

Increased transformer winding losses are an important consideration in determining the overall impact of harmonic currents in a power system. Frequently, losses due to harmonic currents are assumed to vary with the square of frequency. The purpose of this paper is to compare winding loss calculations from a finite element method with measured losses in single phase distribution transformers and to test the principle of superposition of harmonic losses due to nonsinusoidal currents. The results confirm both the finite element method and the principle of superposition. Furthermore, it is shown that, due primarily to inaccuracy in measuring 60 Hz eddy current losses, application of the commonly accepted frequency squared rule can yield overly pessimistic loss predictions for typical power system harmonic frequencies.