kVA Transformer Research Articles

Procedure for Improving the Energy, Environmental and Economic Sustainability of Transformation Houses

A procedure for improving the energy, economic and environmental sustainability of the transformation houses in low-voltage distribution networks is described in this paper. This procedure is based on the reduction of the transformer consumption, copper and core losses. Likewise, the procedure distinguishes between transformation houses with old and new transformers. The reduction of core losses, replacing transformers with others of lower power or that are more efficient, achieves significant improvements in energy and environmental aspects. The reduction of copper losses, and applying reactive compensation techniques, such as harmonic filtering and load balancing, applied in old and new transformation houses, have a greater impact on cost savings, especially when there are capacitive consumptions, as the Circular 3/2020 of the National Markets and Competition Commission of Spain determines. The procedure has been applied to an industrial transformation house, which has an old 1600 kVA transformer, resulting in significant economic savings and CO2 reductions of more than 60%, after replacing the current transformer with a more efficient one.

Influence of the HTS Winding Tape on Limiting the Transient Currents in Superconducting Transformers

The article presents an extended computer model of a HTS (high temperature superconducting) 21 MVA 70/10.5 kV transformer with severalfold compound windings, based on a verified PSpice model of 10 kVA transformer with single windings. Two superconducting tapes: SCS12050 (with a copper stabiliser layer) and SF12050 (without a stabiliser) were used in the windings. The circuit model of the transformer developed in the PSpice environment considers Rhyner’s power law and the Jiles–Atherton description of the magnetic hysteresis loop. Two types of transient states were analysed: switching on a superconducting transformer to the network and an emergency short-circuit of the secondary winding. For the first five unidirectional current pulses generated when connecting an unloaded transformer to the network, the values of the pulse duration (γ angle), the temperature increase in the primary winding as well as the mean and effective values of the switch-on current were calculated. The waveforms of currents, voltages, changes in resistance and temperature during the operation short-circuit were compared for the windings with both types of HTS 2G (high temperature superconductor second generation) tapes. The conducted analysis allowed us to determine the influence of electrical and thermal parameters of the tapes in question on the effective limitation of current in transient states and the possibility of their use in the construction of superconducting transformer windings.

Detection and Classification of Lamination Faults in a 15 kVA Three-Phase Transformer Core Using SVM, KNN and DT Algorithms

This paper deals with the detection and classification of two types of lamination faults (i.e., edge burr and lamination insulation faults) in a three-phase transformer core. Previous experimental results are exploited, which are obtained by employing a 15 kVA transformer under healthy and faulty conditions. Different test conditions are considered such as the flux density, number of the affected laminations and fault location. Indeed, the current signals are used where four features (Average, Fundamental, THD and STD) are extracted. Elaborating A total of 328 samples, these features are utilized as input vectors to train and test classification models based on SVM, KNN and DT algorithms. Based on the selected features, the results confirm that the transformer current can be used for the detection of lamination faults. An accuracy rate of more than 84% is obtained using three different classifiers. Such findings provide a promising step toward fault detection and classification in electrical transformers, helping to prevent the system and avoid other related issues such as the increase of power loss and temperature.

Further Improvements in Topological Transformer Model Covering Core Saturation

This paper is devoted to improvements of the low-frequency topological model of a three-legged stacked-core transformer. It is shown that <i>B-H</i> hysteresis loops employed in the transformer model and &#x03C8;&#x2013; <i>i</i> curves measured at transformer terminals are quite different in shape. A distinction is made between transformer modeling at moderate and deep saturations, separated conditionally by the level of technical saturation (near 2 Tesla) typical for grain-oriented steels. In the former case, in addition to the magnetic coupling of different phase windings through the core, an important part is played by air gaps at core joints. It is found that the effective gap length depends on the instantaneous magnetic flux and this dependence is proposed to implement by variable inductances. It is shown that regardless of the core saturation depth, an important role in the transformer modeling belongs to the distribution of the zero-sequence path between all the phases. In addition to accurate replications of the special purpose saturation test, the modeled results are in a close agreement with positive- and zero sequence data measured on a 50 kVA transformer, as well as with the measured inrush currents.

Redesign The Electricity System of PT Barata Indonesia To Reduce Annual Power Loss

PT Barata is one of Indonesia’s leading turbine component manufacturers, requiring a large amount of electricity for production. Along with the increase in production and factory expansion, the need for electricity continues to increase so that it continues to add power to reach 3780 KVA. One of the weaknesses of the electric power system at PT Barata is using six (6) 20kV/400 V, 630 kVA transformer units. This system produces a no-load or core loss of 8150 Watts. In one year, the power loss reached 71.394 kWh at the cost of IDR 118,514,040.00. Power loss is permanent and lasts all the time during the use of the Transformer. This article aims to redesign the electrical system at PT Barata using a single 4000 kVA transformer. The redesign of the electric power system at PT Barata was carried out by 1. Observing and measuring the electric power system at PT Barata, 2. calculating the resulting losses, 3. conducting studies and designs, 4 comparing the ratio of the total power loss of the electric power system currently with a new design, 5. Propose a redesign to management for implementation. Calculation and analysis of the new design with a 4000 kVA transformer obtained a core loss of 4450 Watt at the cost of Rp. 64,905.030.00, resulting in a savings of IDR. 53,965,980.00 per year. The new design will save 45% in operating costs compared to the previous six transformer units.

Analysis of 11kV/ 430 V 500 kVA Transformer Dissolved Gas using Pre-processing Techniques through Duval’s Triangle

Objectives: Analysis of dissolved gas in transformer oil is very important because the fluctuations in the oil will change the process of content of dissolved gases which will show effect on many factors such as oil temperature and external environment. Hence, it is important to propose a preprocessing technique through Duval’s triangle which is important step in the machine learning process for predictive maintenance of transformer. Methods: The dissolved gas content for 500 kVA transformer oil based on the training and testing data for fault free condition taken for the period of 5 years (2013-17) and faulty condition taken for 3 years (2018-2021), has been evaluated using Duval’s triangle method to express gas concentrations of CH4, C2H2 and C2 H4 in ppm as percentages of their total. High pass filter, scaling and windowing techniques are used for preprocessing the giant DGA data. Findings: The results show that unusual and undesirable intensity in the CH4, C2H2 and C2 H4 gasses is eliminated by using proposed high pass filter technique. More visible output signal by the way of reducing its dimensionality is obtained by applying proposed scaling and windowing techniques for the filtered DGA data. Novelty: Most of the researchers have used limited samples of DGA data for condition monitoring due to which diagnosis of transformer faults is not accurate. To accurately diagnose transformer faults, large set of training and testing data is required. In this paper, the pre-processing of giant DGA data consisting of 960 samples of fault free training with data size of 480000 x 55 and 500 samples of fault free testing with data size of 250000 x 55, faulty training and faulty testing with data size of 960000 x 55 is presented. The preprocessing method adopted will be used in real time application to provide suitable data to train the advanced deep neural network like LSTM through MATLAB interfacingwith graphical processor unit. This is required for condition monitoring and accurately predicting the faults in above mentioned transformer. Keywords: Dissolved Gas Analysis; Duval’s Triangle method; Predictive maintenance; Data Ensemble; Pre-processing; Scaling; Windowing

Design and fabrication of a portable automatic coil winding machine

Purpose The difficulty in winding coil-based electrical and electronic devices manually lies in the fact that it takes so much time and effort to perform. Furthermore, it is difficult to achieve accuracy manually, as it is possible to lose count of the number of turns being wound. The purpose of this paper is to detail the design methods and calculations used to achieve a cost-effective, significantly accurate and more efficient method of winding coils. Design/methodology/approach A program flowchart was designed as a guideline for writing the program. An AT89C52 microcontroller was used to control the movement of the two direct current (DC) motors used in the construction of the machine. The circuit design obtained was then simulated using Proteus to test the functionality of the components together. Findings An electromechanical automatic coil winding machine for the coiling of simple, small-sized, coil-based electrical devices was successfully designed and fabricated. The machine was tested by winding a 1 kVA transformer. Diagrams, calculations, results and observations obtained during the design and construction are detailed in this paper. Originality/value This machine solves the problem of tediousness in coil winding, stably and precisely winding 60 turns/min at a 24 V supply and providing a keypad input method. Although portable automatic coil winding machines have been rendered previously, most have applied the use of stepper motors. The application of brushed DC motors alongside an AT89C52 microcontroller is a variation to the pool of renditions, offering better controllability and a sustained output.

Numerical Study of Cooling by Ferrofluids in an Electrical Transformer Using an Axisymmetric Model

The benefit of transformer oil seeded with magnetic nanoparticles (forming a transformer oil-based ferrofluid) is numerically studied in an axisymmetric model of 40 kVA transformer. The maximum temperature in the system is decreased by 2.2 °C when using ferrofluid instead of transformer oil. This effect is mainly due to the magnetic body force, which modifies the convective flow in the system and enhances heat transfer. The leakage magnetic field is highly localized and limits the effect of thermomagnetic convection. Varying the geometry of the primary coil assembly allows to increase this effect and to decrease the maximum temperature.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ТРИФАЗНОГО ТРАНСФОРМАТОРА З УРАХУВАННЯМ АСИМЕТРІЇ МАГНІТОПРОВОДУ

The paper analyses the aspects of modelling the operation of a three-phase core-type transformer. The features of the magnetic system construction of the transformer, which generate asymmetry, are disclosed. The fundamentals and methods for modelling a transformer in dynamic modes are considered. The main purpose of the paper is to research the influence of taking into account the asymmetry of the transformer magnetic core on its dynamic model. The paper proposes the mathematical model of a three-phase planar core-type transformer, which takes into account the asymmetry of the magnetic core. The mathematical model is based on the model of a generalized electric machine in the ABC axes, which is widely recognized and characterized by a high level of adequacy. A refined model, which takes into account the power losses in the magnetic core, has used. As is well known, such a model is characterized by higher accuracy and adequacy in the calculation of transient processes. For the proposed mathematical model, a comparative analysis of the calculated curves of transient processes for a 63 kVA transformer with a voltage of 6 / 0.4 kV is made. To disclose the effect of taking into account the magnetic core asymmetry of the transformer in the mathematical model, the current differences were calculated in pu for the modes of switching on at full power and three-phase short circuit. These modes are the most common and indicative in the analysis of the operability and stability of transformers. It was found that the most significant difference, which is obtained by taking into account the magnetic system asymmetry of the transformer, is 5…6% when it is switched on at full load. Thus, the relatively simple transformations and updating of the mathematical model of the transformer allow significantly increase its adequacy. The proposed mathematical model can be more effectively used when the non-typical design of three-phase transformers or reactors with significant asymmetry of the magnetic core is considered.

Review of methodologies used for detection of magnetising inrush and fault conditions in power transformer

Reliable and dedicated protection of the transformer is the main requirement in the power system due to the supervision of a highly expensive equipment transformer. Non-linear characteristics of the transformer give mysterious behaviour for the period of inrush and Current transformer saturation conditions. As a stagnant and electro-magnetic device, a transformer is mainly affected by self-inrush. The saturation of the core itself is a very critical situation that becomes a hindrance for fault discrimination. This article involves the elaboration of the effect of inrush on transformer operation, past research practices for the discrimination of inrush with the faulty condition, and a definite method to recognise inrush and fault condition of the transformer. More than 50 reputed journal articles, various book chapters, and books with research thesis thoroughly studied to review the inrush and fault discrimination conditions. A comparative analysis is prepared to suggest the identification of transformer abnormalities. Moreover, a total harmonics distortion (THD)-based solution proposed for discrimination of the inrush condition from fault and other abnormal conditions using the short time Fourier transform technique. Hardware setup for 2 kVA transformer developed in the laboratory to study different inrush phenomena and altered fault conditions. Simulation and hardware results show various effects of inrush and fault with individual harmonic and THD-based analysis. The collection of real-time data is further used based on laboratory hardware setup to enhance real-time protection schemes for power transformers.

Seismic retrofit of 3000 kVA power transformer using friction dampers and prestressed tendons

This study proposes a seismic retrofit system for large power transformers with 3000 kVA capacity. The seismic protection system is developed by combining rotational friction dampers and the pre-stressed tendons with high damping rubber pads at the base. The proposed system enhances the seismic performance of the transformer by limiting the lateral and vertical deflection during earthquakes. The numerical model of the retrofit system is developed and compared with the sub-assemblage test of the damper. The seismic performance of the 3000 kVA transformer retrofitted with the proposed retrofit system is evaluated by performing full-scale shaking table test, and the results are compared with those obtained by the analytical model. The experimental and numerical results demonstrate that the seismic retrofit system is effective in reducing the deflection and acceleration of the transformer when subjected to severe ground motions.

PENGARUH PEMBEBANAN TERHADAP NILAI RESISTANSI PENTANAHAN TRANSFORMATOR 250 KVA PADA GARDU BA 0005 PT. PLN (PERSERO) UP3 BENGKULU ULP TELUK SEGARA

A distribution transformer as an electromagnetic device that converts and transfers electrical energy to the primary and secondary electrical distribution networks, is directly related to the ever changing load center. As a result of high loading and unbalance will cause an increase in neutral induced currents, of course, to anticipate changes in load that cause neutral phase currents in distribution transformers required grounding resistance values or low grounding in the neutral phase.The resistance value or grounding resistance according to the General Electrical Installation Requirements (PUIL) 2000 and SPLN3-1978 Regarding PLN Low Voltage Network Grounding and Installation Grounding does not exceed 5 ? or a maximum of 5 ?. The calculation results obtained the value of the grounding resistance in the neutral phase and the transformer body 250 KVA BA 0005 Distribution Substation, namely 4.11 ?. From these results it is necessary to have a comparative study of the resistance value from the calculation results with the value of the direct measurement results in the neutral phase grounding system and the 250 KVA transformer body BA 0005 Distribution Substation. From the results of direct measurements between 14.00 to 15.00 WIB with 50 percent loading on The transformer has the largest value of resistance in the neutral phase of 8.1 ? and on the transformer body of 8.3 ?. Keywords: 250 KVA Transformer, Grounding Resistance, Neutral Phase, Body Transformer

An Advanced Wideband Model and a Novel Multitype Insulation Monitoring Strategy for VSC-Connected Transformers Based on Common-Mode Impedance Response

The insulation monitoring technique for converter transformers has been explored using characteristic harmonics in the voltage source converter (VSC) system by the authors. The previous work enables the monitoring of aged groundwall insulation but cannot cover other insulation components. In order to explore the possibility of multitype insulation aging monitoring, in this article, we first derive an advanced model considering unevenly distributed circuit parameters along transformer windings and their frequency-dependent feature. Model improvements provide an accurate tool to describe multitype insulation in a wide frequency range. Based on the advanced model, a novel wideband common-mode (CM) impedance-response-based monitoring strategy for the VSC-connected transformer is proposed to achieve the evaluation of the aging in different insulation components. An illustrative case is studied on a 15 kVA transformer driven by an industrial inverter. Offline and online experiments are conducted to prove the effectiveness of the advanced model and the proposed strategy. Compared with the existing methods, the CM impedance-response-based strategy enables the online monitoring of multitype insulation components in an effective and noninvasive manner. In addition, the aging severities can be estimated reliably, even at incipient stages.

Evaluating critical characteristics of vegetable oil as a biodegradable insulating oil for transformer

Abstract In transformer, fuel based mineral oil is used as insulation and coolant over many years. The ecological issue related with the current liquid insulation system is the throwing away of used oil samples after drawn out service. The paper investigates the critical properties of biodegradable oil such as olive and palm oil according to international standards. After that, a small laboratory setup of 1 kVA transformer was designed for the load test with insulating fluids with olive oil and palm oil were tested. Likewise, an attempt has been made for the technical feasibility of mixing proportion was also investigated. Then, the experimental results were compared with mineral oil. Experimental analysis shows that vegetable oil’s electrical and fire resistance properties are better than the conventionally present used mineral oil. Yet, the viscosity of vegetable oil is much higher than mineral oil. Added to that, vegetable oils are exhibiting the higher amount of higher molecular fatty acids. From the load test, it is found that transformer with nature ester palm oil has a higher efficiency that of olive oil, but it is found lower efficiency than mineral oil.

Evolutions of microstructure and magnetic properties of heatproof domain-refined silicon steel during annealing and its application

Heatproof domain-refined grain-oriented (DRGO) silicon steel is an ideal material for the manufacture of S15-type ultra-high efficiency transformer with three-dimensional wound-core (TDWC). In this paper, the microstructure, grain orientation, and magnetic performance of 23ZDMH80 heatproof silicon steel during stress-relief annealing were investigated by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) techniques. Based on heatproof DRGO steel, the Epstein-SST (single sheet tester) conversion factor and equivalent magnetic path length were calculated, and then an ultra-high energy efficiency transformer was developed. Results show that, the average size of micrograins in notched region increased from 42.3 μm to 68.2 μm after annealing at 850 ℃ for 0–8 h. The orientations of micrograins grown on large-size Goss grain included not only the non-〈0 0 1〉 orientations, such as {210} 〈−241〉, {215} < 1–20>, and {1 1 0} < 1–12}, which were harmful to the magnetic properties, but also the favorable {1 0 0} 〈0 0 1〉 and Goss. Correspondingly, the core loss of 5 pairs of Epstein specimens first decreased then increased slowly (the growth rates below 1.2%) during annealing. The Epstein-SST conversion factor δP for 23ZDMH80 heatproof steel was 8.6% (higher than 5.0% the value recommended by IEC standard), and the equivalent magnetic path length was 0.489 m. Finally, the developed 10 kV/400 kVA transformer with TDWC presented ultra low no-load loss of 289 W, load loss of 3072 W, and noise of 35.4 dB, it means significant advantage of energy conservation and environmental protection.

Master Installation Design And Transformer Need Analysis in Faculty of Engineering Udayana University Denpasar

Faculty of Engineering, Udayana University, PB. Sudirman Denpasar has 5 building units (buildings A, B, C, D, AF). Currently the AF building is undergoing renovation and is planned to be on 4 floors. The entire building will be equipped with the installation of 2 elevator units. The construction of the two new buildings and the installation of the 2 elevator units caused new problems of electricity shortages, changes in safety settings, unbalanced loads, and changes in the size of the main cable and the needs of the transformer and its capacity. The AF building and building A are supplied from sources on the transformer which are joined with other faculties, while Buildings B, C, D and E are fed by one transformer No. 124303818 with a capacity of 160 kVA. The plan to build an Alumni Building does not yet have electricity.&#x0D; Based on the analysis of the design, the total amount of power needed in all buildings in the Sudirman Denpasar Faculty of Engineering is the result of the AF Building planning = 134,280 watts, the Alumni Building planning results (building area and building functions are considered equal = 134,280 watts), so the total needs power to the two buildings = 271 560 Watt with a load deviation of 65%, then 0.65 x 271 560 W = 176 514 Watt. Then the total power requirement of the entire building is 259,340 watts. The measurement result of Cos ? 0.92, then P (kVA) = 281,891,3043 Ampere = 281,8913 kVA. So that the transformer needs that must be prepared by the Faculty of Engineering to meet the power requirements at the Faculty of Engineering, Udayana University Denpasar with 80% transformer efficiency is a 350 kVA transformer with a placement position around the Faculty of Engineering area

Studi Analisis Dampak Overload Transformator Terhadap Kualitas Daya Di PT. PLN(Persero) Up3 Pondok Gede

The population of the population in big cities, special areas of the big cottage growth continues to increase according to the BPS in 2015 amounted to 2,733,240 and increased in 2019 3,013,851. With an increasing population, it will increase electricity demand in the region. The JS 190 Distribution Station provided a significant increase in transformer loading which achieved a 95.75% loading presentation of a 200 kVA transformer capacity. Therefore it is necessary to improve by looking at these conditions, one of which is by doing an uprating transformer or adding a power transformer with a larger capacity to 400 kVA. From the results of the increase obtained loading results decreased to 52.75% which means the reversal transformer is one method that can be used to overcome the overload.

Estimation of the eddy current losses in a dry-type 3000 KVA transformer with machine learning

This paper explores the design parameters of high-voltage coils of three-phase transformers and the effects of eddy current losses caused by energy conversion. The commercial software, ANSYS-Maxwell, was employed to conduct the simulation of electrical and magnetic fields. The design parameters of the high voltage coil include the leg distance of core, the height and the block thickness of primary windings, the height of primary coils, and the height of secondary windings. The specification of the three-phase transformer of this study are 3000 kVA with rated voltage of 6600 V and corresponding current of 151.5 A. Base on thirty cases of simulation, machine learning, artificial neural network, was utilized to predict the extra loss due to eddy current in the clamps and the windings. The prediction accuracies are 0.72 and 0.86 for primary and secondary windings, respectively.

Determination of maximum level of EV penetration with consideration of EV charging load and harmonic currents

In order to accommodate Electric Vehicles (EVs) charging demand which is expected to rise steeply in the coming years due to environmental concerns on global warming, it is important to determine the maximum EV penetration can be allowed without network upgrading and avoid overloading of Medium Voltage (MV) cables and distribution transformers in residential distribution power systems. Previous work on modelling and analysis of relationship between the temperature of MV cables and transformer with EV penetration level failed to consider the contribution of harmonic distortion in the demand. In this paper, a methodology is proposed to model the EV penetration and their effects on operational temperature of MV cables and transformers, with charging scenarios and harmonic currents taken into consideration. The method is simulated in a typical urban residential distribution system. The results show that EV penetration above 27.25 % with 6.6 kW EV chargers charging in uncontrolled domestic scenario will lead to 10 kV 400 mm2 three core cable overloading in the simulation with harmonic current taken into consideration. The result is 30.74 % if harmonic currents are ignored. The maximum allowable EV penetration of 35/10 kV 16 MVA and 10 kV 1250 kVA transformer is 50.22% and 26.19% respectively. If EVs charge in off-peak time, the cable and transformer can avoid overloading and the charging cost is lower.

Modifying the thermal performance of electrical distribution transformers using phase change materials (paraffin wax)

AbstractIn this paper, an electrical distribution transformer has been studied experimentally and a novel technique has been proposed to enhance its cooling performance by addition of paraffin wax to transformer oil using closed containers made of aluminum. These containers were immersed in the transformer oil. A 100 kVA transformer was used as a model for study because these transformers are widely used in the electricity distribution network in Iraq. As temperature rises, the phase change material (paraffin wax) absorbs heat and melts inside the containers at a constant temperature. This feature can be utilized to store heat for a period until the temperature for weather drops; then this heat is rejected, and the wax begins to solidify. In this experiment, five containers were used, each containing 2 kg of wax. The results showed a clear decrease in the temperature of the oil, which led to the enhancment of its thermal insulation and kept the oil from failure and the preserved the transformer from breakdown. The results showed that the reduction in temperature is approximately 7°C and the reduction increased upon increasing the amount of wax added.