Distribution Transformer Loss Research Articles

The Reduction Method of a Stray Load Loss of Distribution Transformer on the Bushing Flange Plate with STS

This paper deals with the stray load loss on the bushing flange plate of low voltage side for high efficiency of the distribution transformer. To reduce the magnetic flux concentration, three models are proposed as follows. First, the basic transformer model is designed which is consisted of the windings, the core, the case and the bushing. Second transformer model is designed to creating a slit at the area where the magnetic flux on the bushing flange plate is concentrated and then attaching the STS (Stainless steel). In the third model, the bushing flange plate around the bushing terminal is cut into a large square shape and STS is attached. As a result of the simulations, when the material of the case is only steel, the stray load loss is 10.56 W, while the case with STS slit is 1.49 W and the case with STS plate is 0.17 W. The stray load loss reduction rate was 85.9% and 98.4% compared with the steel plate model. It is also verified by the load test using the distribution transformer based on simulation data.

Cost-optimal as a tool for helping in designing distribution transformer using particle swarm optimization

PurposeThis paper aims to achieve an optimal design for distribution transformers considering cost and power losses. Particle swarm optimization (PSO) algorithm is used as an optimization tool for minimizing the objective functions of design procedure which are cost and electrical and iron losses.Design/methodology/approachIn this paper, distribution transformer losses are considered as operating costs. Also, transformer construction cost which depends on the amount of iron and copper in the structure is assumed as its initial cost. In addition, some other important constraints such as appropriate ranges of transformer efficiency, voltage regulation, temperature rise, no-load current, and winding fill factor are investigated in the design procedure. The PSO algorithm is applied to find optimum amount of needed copper and iron for a typical distribution transformer. Moreover, transformer impedance considered as a constraint to achieve an acceptable voltage regulation in the design process.FindingsIt is shown that the proposed design procedure provides a simple and effective approach to estimate the flux and current densities for minimizing the active part cost and active power losses which means reduction in amount of transformer total owning cost (TOC).Originality/valueThe methodology advances a proposal for reducing distribution transformers costs using PSO algorithm. The approach considers the aforementioned constraints and TOC to minimize the active part cost and maximize the efficiency. It is demonstrated that a designed transformer will not be optimum when the transformer losses over years are not considered in design procedure. Finally, the results prove the effectiveness of the proposed procedure in designing cost-effective distribution transformers from its initial cost until its whole life.

Distribution Transformer's Loss of Life Considering Residential Prosumers Owning Solar Shingles, High-Power Fast Chargers and Second-Generation Battery Energy Storage

In this study, the effect of the electric vehicle high-power fast chargers in the residential sector on the aging of distribution transformers is probabilistically quantified. This work takes into consideration the presence of the traditional rooftop solar photovoltaic panels and the most recent technology namely rooftop solar shingles used in residential prosumers (power producers and consumers). Moreover, the effectiveness of the second-generation residential home and community battery energy storage, installed in the residential prosumers and in the electric utilities’ premises, in preserving the distribution transformer's lifetime is discussed and conclusions are drawn.

A Simulation Scheme for Unordered Power Charging Of Electric Vehicles On Distribution Power Network

With the lack of support for new energy electric vehicles (EV) and the continuous introduction of new policies, EV are entering a period of rapid development. However, the large number of unordered access distribution network of EV users in the period will have a great impact on the power distribution network. EV will further aggravate the load peak valley of the grid during peak periods. It may lead to a series of problems such as overload of distribution network line, voltage drop, increase of distribution network loss and overload of distribution transformer. This paper makes an in-depth analysis of the influence of unordered access charging on power distribution network from theoretical and practical perspectives. For example, Network load, voltage, line loss, etc. Based on the analysis results, a smart charging station based on variable distribution is proposed. It is the best solution to solve the current problem by intelligent orderly control method.

HTS Transformer Windings Design Using Distributive Ratios for Minimization of Short Circuit Forces

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 components of short-circuit electromagnetic forces in an HTS transformer are significantly reduced. Two- and three-dimensional (2D and 3D) finite element method (FEM) simulations are employed to verify the analytical method results.

Analysis of the Effect of an Installation of a Single Tuned Passive Filter on Harmonics and Distribution Transformers

<span>Non-linear loads on power systems cause harmonics and losses in distribution transformers. Results of the measurements on the two distribution transformers showed several phase transformer test-driven development (TDD) values above the standard SPLN D5.004-1: 2012. The values were 5.58% in the phase transformer, T 1 and 5.48% and 6.10% in S and T phases of the second transformer, respectively. In the calculations, the transformer losses due to harmonic currents were 1.64 kW in the phase transformer T 1, and 1.64 kW and 1.82 kW in the S and T phases of transformer 2, respectively. Designing a single-tuned passive filter based on the characteristics of the current, voltage, power, and power factor in the phase transformer with a value above the TDD standard can reduce the harmonics and losses. A filter with different specifications in each filtered phase transformer was obtained. The filter reduced the TDD value on the phase transformer T 1 to 3.55% and to 3.88% and 3.43% on the on phase T and S phases of transformer 2. Moreover, it reduced the losses to 0.73 kW on phase transformer T 1, and 1.02 kW and 0.92 kW on the S and T phases of transformer 2. </span>

Optimal Planning Method of On-load Capacity Regulating Distribution Transformers in Urban Distribution Networks after Electric Energy Replacement Considering Uncertainties

Electric energy replacement is the umbrella term for the use of electric energy to replace oil (e.g., electric automobiles), coal (e.g., electric heating), and gas (e.g., electric cooking appliances), which increases the electrical load peak, causing greater valley/peak differences. On-load capacity regulating distribution transformers have been used to deal with loads with great valley/peak differences, so reasonably replacing conventional distribution transformers with on-load capacity regulating distribution transformers can effectively cope with load changes after electric energy replacement and reduce the no-load losses of distribution transformers. Before planning for on-load capacity regulating distribution transformers, the nodal effective load considering uncertainties within the life cycle after electric energy replacement was obtained by a Monte Carlo method. Then, according to the loss relation between on-load capacity regulating distribution transformers and conventional distribution transformers, three characteristic indexes of annual continuous apparent power curve and replacement criteria for on-load capacity regulating distribution transformers were put forward in this paper, and a set of distribution transformer replaceable points was obtained. Next, based on cost benefit analysis, a planning model of on-load capacity regulating distribution transformers which consists of investment profitability index within the life cycle, investment cost recouping index and capacity regulating cost index was put forward. The branch and bound method was used to solve the planning model within replaceable point set to obtain upgrading and reconstruction scheme of distribution transformers under a certain investment. Finally, planning analysis of on-load capacity regulating distribution transformers was carried out for electric energy replacement points in one urban distribution network under three scenes: certain load, uncertain load and nodal effective load considering uncertainties. Results showed that the planning method of on-load capacity regulating distribution transformers proposed in this paper was very feasible and is of great guiding significance to distribution transformer planning after electric energy replacement and the popularization of on-load capacity regulating distribution transformers.

Effects of voltage harmonic on losses and temperature rise in distribution transformers

The effects of harmonic pollution in the power system on distribution transformer losses and temperature rise have become an increasing concern. The pollution can be in the form of current and/or voltage harmonics present in the supply networks. Since the impact of voltage harmonics has hardly been investigated, this study examines the effects of distorted voltage excitation on oil-filled distribution transformers. Short-circuit and open-circuit tests were conducted on two distribution transformers. The results revealed significant increase in both losses and temperature. An equation is developed to quantify the power loss. This study also derives an equation to evaluate the resistance corresponding to the eddy-current loss.

Determination of Capitalization Values for No Load Loss and Load Loss in Distribution Transformers

A large number of distribution transformers are being currently used in the electricity distribution network in Sri Lanka. When purchasing them, it is not sufficient to evaluate only the initial price of the transformer. There are no load losses as well as load losses in the transformer during its life span, which is about 35 years. Therefore, a transformer purchaser has to evaluate the total lifetime cost of the transformer, which includes its purchase price, and the cost of losses that can occur during the life of the transformer. Traditionally, this evaluation has been done based on the Total Owning Cost (TOC). This paper discusses setting up of a methodology to calculate capitalization values for losses in distribution transformers used in Sri Lanka, using IEEE loss evaluation guide. Capitalization values for distribution transformers depend on capacity and energy costs, economic considerations and on their load profiles. In this research, capitalization values are calculated for three different load profiles of the transformers installed in rural, semi-urban and urban areas of Sri Lanka. In future, any utility can purchase distribution transformers by calculating capitalization values using the methodology presented in this study which is based on a set of economic and other parameters suitable for different applications, i.e. rural electrification, loss reduction in urban cities, augmentation of distribution transformers, etc.

Losses in Power Distribution Transformers

The paper presents the estimation of power losses in distribution transformer of Provincial Electricity Authority (PEA) distribution system at Muang district of Suphanburi province in Thailand. Data of 416 power distribution transformers composed of transformer (kVA), load current, no load loss and full load loss which were used for calculating energy losses. It was found that the total energy loss of all transformers is approximately 1,756,380 kWh/year.

English

English

Estimation of Distribution Transformer Losses in Feeder Circuit

Losses of distribution transformers (DT) in a distribution system (DS) depend on mainly load. Actual measurement of these losses is in substation (SS) feeder circuit is not easy due to many inconveniences like difficulty in installation of meters, unfavourable locations and conditions. But as the DT losses are sizeable they need to be considered for overall loss calculations. In this paper, an approach is developed to estimate the DT losses in a feeder circuit. Losses of individual DTs are calculated and summed up to give the losses due to DT circuit. A sample case of a large power system is considered. The losses are calculated by the said approach. The overall DT circuit losses are 8.57% of the total import.

A Control Device for Distribution Transformer Neutral Current and Loss

This paper develops a control device for distribution transformer neutral current and loss caused by unbalanced loads. Due to multi-objective optimization, its control strategy is designed, considering the reliable operation of distribution transformers and its performance. This device can gather power quality parameters, calculate the optimal regulation and control capacitor switching, which consists of power quality acquisition unit, central processing unit (CPU), capacitor control cabinet and power supply. After simulation and experiment, the result shows device can achieve target by dynamic adjustment.

Parallel distribution transformer loss reductions: A proposed method and experimental validation

Transformers in electrical distribution systems for buildings and industries are set up to ensure the continuity of supply. Modern distribution transformers are reaching increasingly higher levels of energy efficiency but contribute to between 16% and 40% of the energy losses associated with electrical distribution systems. This paper examines and proposes a method to reduce losses in transformation systems and thus to reduce the associated emission of greenhouse gases (GHGs). This paper proposes a method of system optimization for transformers in parallel, called Parallel Losses Optimization (PLO), and is applicable to existing or future facilities and is adaptable to any type of transformer system. The method has been validated in 12 real facilities of different power and efficiency levels. Reductions in the losses of the studied transformers were up to 41% with respect to the initial losses. This demonstrates the beneficial operation of the PLO method proposed in this paper in a wide range of existing transformers or for future installations. The research has obtained patent pending status P201101267 in Spain.

A novel neutral current control scheme for three-phase four-wire distribution transformers

The neutral current can significantly harm the operation of a system, increase the losses of distribution transformers, and reduce the energy efficiency of a system. These negative effects of the neutral current highlight the importance and necessity of investigating neutral current control strategies. In this paper, we propose a novel scheme for controlling the neutral current caused by a linear unbalanced load in three-phase four-wire distribution transformers. The scheme, which is based on the static var compensator (SVC) technology, aims to: (i) control the neutral current, and (ii) reduce distribution transformer losses. It takes into account the effects of unbalanced fundamental currents and the SVC's compensating capability. Combining optimisation theory with a sequential quadratic programming method, we derive the optimal solution for the current control scenario we studied in this work. Simulation results show that our neutral current control scheme can significantly reduce the neutral current and distribution transformer losses. We also present some interesting observations on the SVC's capability and its significant impact on the neutral current and energy efficiency of a system. We hope that our work will encourage future research on SVC-based neutral current control approaches. © Institution of Engineers Australia, 2013.

A Novel Neutral Current Control Scheme for Three-Phase Four-Wire Distribution Transformers

The neutral current can significantly harm the operation of a system, increase the losses of distribution transformers, and reduce the energy efficiency of a system. These negative effects of the neutral current highlight the importance and necessity of investigating neutral current control strategies. In this paper, we propose a novel scheme for controlling the neutral current caused by a linear unbalanced load in three-phase four-wire distribution transformers. The scheme, which is based on the static var compensator (SVC) technology, aims to: (i) control the neutral current, and (ii) reduce distribution transformer losses. It takes into account the effects of unbalanced fundamental currents and the SVC’s compensating capability. Combining optimisation theory with a sequential quadratic programming method, we derive the optimal solution for the current control scenario we studied in this work. Simulation results show that our neutral current control scheme can significantly reduce the neutral current and distribution transformer losses. We also present some interesting observations on the SVC’s capability and its significant impact on the neutral current and energy efficiency of a system. We hope that our work will encourage future research on SVC-based neutral current control approaches.

Effect of Modeling Non-Normality and Stochastic Dependence of Variables on Distribution Transformer Loss of Life Inference

This paper presents a method for transformer loss-of-life inference by integrating stochastic dependence between non-normal transformer load and ambient temperature into analysis. The non-normally distributed variables are transformed to a common domain (i.e., the rank domain) by applying the cumulative density function transformation. In this domain, special functions, copulas, are used for modeling stochastic dependence between the variables. Extensive research data have been used to obtain quantitative results for realistic test cases of distribution transformers serving various types of low-voltage consumers. The results indicate that the accuracy of loss-of-life inference is very sensitive to normality and independence assumptions which are generally adopted in previous studies. It is demonstrated that such assumptions may lead to misleading results compared to the actual conditions. Thus, the proposed method, which is based on no restrictive assumption, emerges as a more accurate solution for transformer loss-of-life inference.

Reduction of Power Grid Losses by Using Energy Efficient Distribution Transformers

The importance of distribution transformer no-load loss on the operation of modern electrical grids is often underestimated. Internationally, distribution transformer no-load loss constitutes nearly 25% of the transmission and distribution losses of electrical grids. The losses in European Union distribution transformers are estimated at about 33 TWh/year whereas, reactive power and harmonic losses add a further 5 TWh/year. In the Greek electrical grid the no-load losses of 140,000 distribution transformers are estimated at about 490 GWh/year. This paper has two goals the first one is to illustrate the significance of distribution transformer no-load loss in periods of high electric energy cost and the second goal is the presentation of a novel numerical methodology for wound core transformers no-load loss analysis, enabling to determine the economically and technically optimum transformer for every use.

Transformer Joints FE Analysis Using Pseudo-Source Technique

Distribution transformers losses are equal to almost 2% of the electricity generated worldwide and only in the European Union are estimated at about 33 TWh/year. Approximately 75% of the total losses are due to core losses as a result of the loading characteristics of distribution transformers. Design of the joints of magnetic cores has a profound impact on core losses and transformer efficiency. The paper introduces a finite element methodology for the analysis of transformer joints. The proposed technique consists in the application of certain boundary conditions for the excitation of the joints. The main advantages of the pseudo-source technique include minimization of the computational cost and ease of implementation. The technique is combined with a number of FE formulations and a vector hysteresis model. Two-dimensional as well as 3-D FE analysis is studied. Longitudinal and normal flux measurements were carried out for the validation of the proposed technique.

Environmental cost of distribution transformer losses

Improvements in energy efficiency of electrical equipment reduce the greenhouse gas (GHG) emissions and contribute to the protection of the environment. Moreover, as system investment and energy costs continue to increase, electric utilities are increasingly interested in installing energy-efficient transformers at their distribution networks. This paper analyzes the impact of the environmental cost of transformer losses on the economic evaluation of distribution transformers. This environmental cost is coming form the cost to buy GHG emission credits because of the GHG emissions associated with supplying transformer losses throughout the transformer lifetime. Application results on the Hellenic power system for 21 transformer offers under 9 different scenarios indicate that the environmental cost of transformer losses can reach on average 34% and 8% of transformer purchasing price for high loss and medium loss transformers, respectively. That is why it is important to incorporate the environmental cost of transformer losses into the economic evaluation of distribution transformers.