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The paper develops a model created in Simscape – SIMULINK to study the monophase transformer behaviour. The equivalent circuit topology of a typical transformer needs to implement a procedure to determine the values for equivalent circuit elements based on performance criteria. The preliminary tests need in study of behaviour 's transformers are open-circuit and short-circuit tests. The paper implements a model realised with Simscape block offered by MATLAB library used for modelling the transformer 'behaviour described on laboratory tests. [ABSTRACT FROM AUTHOR]

Highlights • Establishing the three-phase equivalent mathematical model for CIPF. • Revealing the distinctive operational mechanism of the CIPF method in a mathematical sense. • Finding out the operational law. An improved control strategy is designed. Abstract This paper presents a controllable inductive power filtering (CIPF) system with the novel filtering mechanism. Due to the zero-impedance design of the power transformer, the harmonic magnetic flux between the secondary load winding and the customized filtering winding can be balanced each other. Hence, the contaminated area of harmonics is reduced. The addition of the active filter contributes to further improve the filtering performance with the task of harmonic isolation between the power grid and the load. First, the three-phase unified equivalent circuit model and the mathematical model are given out at the harmonic domain. Based on the deduced transfer matrix, the filtering evaluation criterion of CIPF system is established, and the filtering principle is revealed, as well. According to the special operational law, an improved virtual impedance control strategy is designed to prevent the potential harmonic amplification, and the relationship between the phase/magnitude of the virtual impedance and the filtering performance is discussed. Finally, the experimental results based on the laboratory scaled prototype show the validity of the CIPF system with improved virtual impedance control. [ABSTRACT FROM AUTHOR]

In this paper, we report on the experimental study of the direct current electrical conduction in a magnetic nanofluid based on transformer oil and iron oxide nanoparticles stabilized with oleic acid. We present the current–voltage characteristics of the pure transformer oil and the magnetic nanofluid with various particle volume fractions. From the Ohmic region, we calculate the electrical conductivity values and confirm the effect of increasing conductivity with increasing particle volume fraction. A few sources of space charge have been taken into account, among which the ion impurities play the key role. It was found that the current–voltage characteristics exhibit the inverse hysteresis-like behavior. Then, we focus on the magnetic field influence on the hysteresis behavior of a selected sample. The external magnetic field was applied in both, parallel and perpendicular configuration in regard to the electric field direction. It is shown that the magnetic field acting on the magnetic nanofluid in the perpendicular configuration results in the remarkable thinning of the current–voltage inverse hysteresis loop. [ABSTRACT FROM AUTHOR]

To represent transformer behaviour during a transient state which includes high frequencies, it is necessary to consider the resonances which occur inside the transformer. One strategy is to deduce the transformer model from the measurements of the transformer’s frequency response, another one is to construct the model based on a careful representation of the inside of the apparatus. In the paper a model is presented which is compatible with EMTP-type software programs based on a finite element method (FEM) calculations and the complex permeability approximation. The model can be classified as a Grey Box transformer model, according to the terminology of the CIGRE. The model’s frequency dependent parameters are derived from limited information about the transformer geometry. State space equations are used to input the model into an electromagnetic transient calculation software program. This approach requires specific mathematical treatments to avoid stability issues during simulations. The model is validated for lightning impulse studies using the field test measurements of over-voltages that had occurred at the external transformer’s terminals. [ABSTRACT FROM AUTHOR]

This work has two main contributions; First, the development of a general, exact and standardized Step Voltage Regulator model considering all possible configurations and second, the proposal of a 4-Node Test System for testing and evaluation of three-phase Step Voltage Regulator connections. Although the 4-Node Test Feeder for testing three phase transformer configurations is already available in the literature, there is not such model for the inclusion, testing and validation of Step Voltage Regulators in a test feeder. With the work presented in this paper, a new test system will be available to evaluate and benchmark programs or algorithms that attempt to include different configurations of Step Voltage Regulators. The formulation is stated for all three phase Step Voltage Regulators; i.e. wye, close-delta and open-delta connections, both type A and B regulators, in raise or lower positions. Then, all these models are included in a 4-Node Test Feeder to obtain several power flow solutions. All obtained results will be available for power flow software developers on-line. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive state-space dynamic model of a future power distribution system for plug-and-play interface of distributed renewable energy resources and distributed energy storage devices. The system, called the future renewable electric energy delivery and management (FREEDM) system, comprises of multiple solid-state transformers (SSTs), and load, generation, and storage connected to each SST in a distributed network. The system allows for high penetration of renewable generation with energy storage at the distribution level. A physics-based 70th-order state-space average model is first developed considering the physical and controller properties of a single-SST FREEDM system along with its distribution components. This fundamental model is then extended to build a multi-SST FREEDM system for feasibility and dynamics behavior analysis of the entire system, which is essential to ensure system power balance. The full average model with multiple SSTs has been incorporated in an IEEE 34 bus distribution testbed for a scaled analysis of the system. [ABSTRACT FROM AUTHOR]

This study presents a probabilistic response analysis of seismically isolated electrical transformers with emphasis on comparing the performance of equipment that are non-isolated to equipment that are isolated only in the horizontal direction or are isolated by a three-dimensional isolation system. The performance is assessed by calculating the probability of failure as function of the seismic intensity with due consideration of: (a) horizontal and vertical ground seismic motions, (b) displacement capacity of the seismic isolation system, (c) limit states of electrical bushings, (d) details of construction of the isolation system, (e) weight of the isolated transformer, and (f) bushing geometry and configuration. Calculations of the probability of failure within the lifetime of isolated and non-isolated transformers at selected locations are also performed. The results of this study demonstrate that seismic isolation systems can improve the seismic performance for a wide range of parameters and that systems which isolate in both the horizontal and vertical directions can be further effective. The seismic assessment methodology presented can be used for: (a) deciding on the need to use seismic isolation and selecting the properties of the isolation system for transformers depending on the design limits, location, and configuration of transformer and (b) calculating the mean annual frequency of functional failure and the corresponding probability of failure over the lifetime of the equipment. The results may also be used to assess the seismic performance of electric transmission networks under scenarios of component failures. [ABSTRACT FROM AUTHOR]

Ultrasonic method of detecting PD is based on the fact that the electrical energy of the PD transforms in a mechanical energy, an ultrasonic acoustic wave that spreads through the transformer to the tank wall. These mechanical waves are detected with piezzo-electric sensors and transformed into electrical signals which are processed with a special instrument called Acoustic Emission System (AES). Since not only defects inside the transformer can produce acoustic waves, during analysis there is a problem distinguishing the actual origin of the detected acoustic waves. Therefore, additional sensors can be added to the system which monitor some parameters of the transformer such as temperature of the tank, load, OLTC operations, fan and pump operations, PD level during laboratory testing (in accordance with [1]) etc. These parameters can simplify analysis using a time correlation between detected hits (hit is a designation for event when sensor detects an acoustic wave) and in-service parameters of the transformer. Another problem with location of the source in 3D system is the lack of knowledge of the zero time of the hit. Using a high frequency current transformer (Rogowski coil) and the fact that the electric signal has a high propagation velocity, zero time can be added to the system providing higher accuracy. [ABSTRACT FROM AUTHOR]

Harmonics produced by residential loads have become an increasing concern in recent years due to the extensive adoption of power-electronic-based home appliances. This paper presents analysis on extensive field data collected from various locations of residential distribution systems in North America. The degree of cancellation of harmonic currents from different sources is determined. A comparative study on the harmonic characteristics of residential, commercial, and industrial feeders is also conducted. The results show that the harmonic current distortion levels of residential feeders are much higher than those of the industrial and commercial feeders. The third harmonic is the most pronounced component and the low-order harmonic currents from different homes tend to add to each other, i.e., the harmonic cancellation effect is much less than those claimed in the literature. [ABSTRACT FROM PUBLISHER]

In this paper, a new adaptive single-phase reclosing method for high-voltage transmission lines is proposed. This method employs local voltage magnitude and angle of the faulted phase. It is shown in this paper that the proposed method is able to quickly identify the fault type and the arc extinction if the fault is transient. This method is effective for various system configurations, including ideally and partially transposed transmission lines, untransposed lines, as well as transmission lines with or without a shunt reactor. Superior performance of the proposed method has been verified using 550 case studies simulated in PSCAD and Matlab and a real case related to a 765-kV transmission line. [ABSTRACT FROM PUBLISHER]

Interline Dynamic Voltage Restorer (IDVR) comprises of several Dynamic Voltage Restorers (DVRs) connected to different distribution feeders in the power system sharing common energy storage. One of the DVR provides for voltage sag compensation appearing in that feeder, while the other DVRs restore the energy in the common dc-link thus dynamically maintaining the voltage of DC link capacitor constant by importing power from the other feeders. Restoration of the DC link energy plays an important role in the capability of the individual DVR in the IDVR to mitigate deep sags with long durations. In this paper the restoration of the DC link energy of the IDVR is achieved by the utilizing the phase shifting transformers (PST) which assist the respective DVR during its power control mode. A controlled switching action is provided to choose the appropriate connection of PST to the feeders depending upon the voltage sag condition. The proposed novel concept is examined in a test power system with IDVR. [ABSTRACT FROM AUTHOR]

The quality of original data is crucial to the performance of diagnosis model. To improve the performance of transformer diagnosis model based on Dissolved Gas Analysis (DGA), a new diagnosis scheme suitable for time-series dissolved gas data is proposed in this paper. After the analysis of traditional transformer diagnosis architecture, a fault data extraction step is added to the architecture to improve the quality of original fault data. The fault data extraction step is mainly composed of two parts, invalid data correction and determination of possible initial fault time based on fault early warning. Finally, the numerical results validate that the accuracy and sensitivity of DGA based fault diagnosis for the transformer are improved by extracting fault feature of time-series data. [ABSTRACT FROM AUTHOR]

An algorithm and a technique are developed for finding the maximum values of the target current components in a MOS transistor with an n-type built-in channel depending on the submicron and nanoscale topological norms for a frequency transformer in the presence of intensive noise at its input. The spectral making components of the intermediate frequency are evaluated and analyzed for the given amplitudes of the generator, signal, and handicap. The behavior of the n-MOS transistors designed according to the GPDK045 and GPDK0990 technological norms is investigated. [ABSTRACT FROM AUTHOR]

This paper presents verification of frequency-response analysis (FRA) and vibroacoustic-method (VM) test methods complementarity for the assessment of the mechanical condition of a transformer's active part. Experiments performed on real power transformers under field conditions are discussed. The presented results cover three cases of faults which would be difficult to detect or correctly interpret with the application of a single method only. The first case shows the interfering influence of radiators on VM results. In the second case, a loosened winding with unchanged geometry, which cannot be detected by the FRA method, is discussed. The third presented case shows the results of an experiment based on introducing faults into the active part followed by FRA and VM tests. These faults were loosening of the core and loosening of winding with its slight stretching. The first fault could only be detected, as expected by VM results analysis, while the second one was confirmed by both methods; however, FRA assessment quality depends on the method of test data comparison. [ABSTRACT FROM PUBLISHER]

A novel optimization-enabled electromagnetic transient simulation approach is proposed for calculating the resistor setting of a multistage impulse generator for insulation impulse testing of high-voltage transformers. This approach enables test engineers to overcome most of the major challenges attributed to the use of conventional trial-and-error methods for determining resistor settings, including the excessive time consumption and the potential damage to the test transformer due to a greater number of trial tests. The proposed method uses the frequency response of the test transformer to synthesize a circuit model for it. The test setup, including the test transformer and the impulse generator, is simulated using an electromagnetic-transients-type simulator. A genetic-algorithm-based approach is used to optimize the setting of the impulse generator. Optimized resistor values are then used in impulse testing of a three-phase power transformer. Different cases of impulse generator resistor arrangements are studied in this paper and simulated waveforms are compared with those obtained from measurements. [ABSTRACT FROM AUTHOR]

The variable frequency power factor (PF) (VFPF), frequency response of stray losses (FRSL), and dynamic dc winding resistance tests are reviewed in this paper. These electrical field tests provide new and significant diagnostic detail and thereby enable a more comprehensive assessment of the condition of a transformer. These tools are not radically different from three standard electrical tests that have been in use for decades in the industry. In fact, the test setup, connections, and test implementation requirements from a tester's perspective are identical to those for the PF, leakage reactance, and dc winding resistance tests, respectively. The subject electrical field tests have progressed from these traditional tests, gaining their unique assessment capabilities by simply expanding the related standard test's measurement(s) in the frequency or time domain. VFPF, FRSL, and dynamic dc winding resistance tests do not displace these older diagnostic tools but rather supplement them, bringing considerable and, in the case of the VFPF test, disproportionately more value. [ABSTRACT FROM AUTHOR]

An accurate transformer model is an important tool for use in the study of power transformers. However, a manufacturer's proprietary restrictions will generally make access to the detailed design specifications of a transformer difficult. Therefore, in order to construct a physically representative transformer model, it is often necessary to estimate the model parameters. One approach is to fit the model to data obtained from tests, such as frequency-response analysis. However, during the process of fitting a model to a data set, it is critical that the estimated parameters appropriately represent the transformer under test. An estimator that is not constrained can converge on a parameter set which may satisfy the objective function but is not physically representative of the transformer. It is therefore important to constrain the model parameters. The aim of this paper is to formulate a methodology to obtain initial estimates and constraints for several fundamental transformer parameters. To demonstrate applicability, the initial parameter estimates and constraints are applied to a range of distribution transformers of varying age and manufacture, ranging in size from 200 kVA to 18 MVA. [ABSTRACT FROM AUTHOR]

An elaborate method to analyze the high-frequency behavior of transformer windings by means of the multiconductor transmission line (MTL) method is presented. A procedure for the evaluation of per-unit length parameters for transformer windings (TWs) is enumerated, which is not available in existing literature on the subject. A full-length detailed solution of the MTL method for TW is also demonstrated. A comparison of this method with the conventional circuit approach is illustrated wherever necessary. The analysis of two types of commonly used interleaved windings is performed in this paper. It is also inferred from experimental results that a conventional low-voltage impulse test is insufficient to make a distinction between the two windings. As far as interwinding oscillations at high-frequency excitations are concerned, it also proved by the MTL analysis that one type is better than the other. [ABSTRACT FROM AUTHOR]

Remote monitoring has been implemented in many areas. This paper introduces its specific application to a three-phase 10-kVA energy-efficient switchable distribution transformer. A designed embedded system and embedded Ethernet have been implemented to achieve a compact remote condition monitoring for the transformer. The embedded system performs acquisition of voltages, currents, and temperatures, controls the switching devices that connect the tappings of the transformer, and processes acquired data. Client and server applications were developed through the use of embedded Ethernet to enable remote monitoring through a local area network (LAN). Some protocols were developed as parts of software development of the whole system. Experimentation was done by applying the remote monitoring system to the transformer connected to three-phase variable supply voltage and load. Results of the experimentation by using a LAN available in the school revealed that the system can handle remote monitoring and control tasks for the transformer. [ABSTRACT FROM PUBLISHER]

To equivalently and effectively test the shielding effect of a heavy current transformer (HCT) with shielding coils in a laboratory, an eccentric bus-bar testing method has been used to simultaneously simulate the effect of primary bus bar and adjacent bus bar since 1970s. However, there has not yet been an effective way to determine the crucial parameters, particularly the eccentric distance, which means the distance from the center of an eccentric bus bar to the center of an HCT. This paper presents several analytical formulas to determine the eccentric distance and relevant parameters in the testing method, which may overcome the difficulty at present. The formulas are derived out from a magnetic circuit model and further verified by a finite-element method. Numerical results show that these formulas are effective and easy to use in the testing of an HCT. Most importantly, the source of an equivalent relative error has been also investigated in detail. Furthermore, if the eccentric current, which should be equal to the original primary current, is still too high to be reproduced in a laboratory, auxiliary and compensating windings could be adopted to reduce it. [ABSTRACT FROM PUBLISHER]

In recent years, more and more transformers are designed with low induction levels and improved core designs. That leads to a change in the contribution hierarchy of the sound sources in transformers. According to the IEC Power transformer standard, the decision as to whether it is significant to perform load current sound measurements is made on a single equation which depends only on the rated power. In this paper we shall suggest, through test examples, that this equation can be misleading and a modified methodology which is based on measurements of noise at both "no-load" and "load" states, is necessary. [ABSTRACT FROM AUTHOR]

Loopback tests for a differential mixed-signal device under test (DUT) have rarely been attempted since any imbalance introduced by design-for-test (DfT) circuitry on differential signaling delivers an imperfect sinusoidal wave to the DUT input or output, thereby degrading the DUT performance. In addition, this methodology inherently suffers from fault masking. These problems trigger low test accuracy and serious yield loss. This paper presents a novel methodology for the efficient prediction of individual DUT dynamic performance parameters with a radio-frequency (RF) transformer in loopback mode to overcome the imbalance of DfT circuitry and the fault masking. Cascaded RF transformers with different multiplicative weights are selected in three combinations by a multiplexer to create three separate loopback responses. These responses are used to characterize the DUT dynamic performance. Hardware measurement results show that this approach can be effectively used to predict the specifications of a DUT. [ABSTRACT FROM AUTHOR]

An augmented short-circuit test is described for the determination of equivalent-circuit parameters of single-phase transformers with large series-branch impedances. This test may be conducted at rated currents with the transformer connected to a reduced voltage supply. Thus harmonics in current and voltage waves are negligible. This test is therefore free from harmonics associated errors. Based on test results, phasor equations are found which give formulae for the equivalent-circuit parameters with series-branch impedance split into low- and high-voltage components. [ABSTRACT FROM AUTHOR]

A significant amount of lightning impulse breakdown and withstand testing has been accomplished in mineral oil to understand this important electrical characteristic for transformer insulation system design. To be considered as viable insulating fluids for high voltage equipment, alternative dielectric liquids should have similar lightning impulse characteristics as compared to mineral oil to provide the clearances necessary for common dielectric design. This paper reviews the testing for establishing the lightning impulse breakdown characteristics of natural ester fluids relative to mineral oil test results. The key variables of the testing included: various oil gap and solid insulation creep distances, electrode configurations, electrical stress characteristics, and solid insulation surfaces. The fluid gaps ranged from 3 mm to 55 mm. The electrode configurations included quasi-uniform in oil gaps, with some attached to pressboard, and nonhomogeneous contacts in oil gaps combined with a phenolic interface. The range in gap distance was selected to reflect the range commonly used in liquid insulated transformer core/coil designs. The electrical stresses used included 1.2 x 50 μs lightning impulses of both positive and negative polarity. The solid insulation materials consisted of high density pressboard, Kraft paper and a high density phenolic composite. it is concluded that the impulse breakdown voltage of the natural ester fluid is similar to mineral oil for the oil gaps and electrode configurations tested. [ABSTRACT FROM AUTHOR]

The results of the developed work for the implementation of the induced voltage test to be applied to single phase distribution transformers in the Researches and Electroenergetic Tests Center (CIPEL) of Cuba, are presented, The test outline was obtained starting from the employment of a motor - generator group, with an external voltage regulator and using a frequency converter to obtain the necessary frequency for this type of test. [ABSTRACT FROM AUTHOR]

Focuses on a study on a risk-based probabilistic method to assess transformer loading capacity, taking into account the probabilistic nature of time-varying loads and ambient temperature. Ways to obtain the probabilistic distribution of hottest spot temperature; Development of a risk assessment model for transformer overloading; Transformer reference risk levels.

Presents a study on the effects of electric vehicle (EV) charging on a substation transformer that supplies commercial, residential, industrial and EV load. How the study was conducted; Evaluation of the effect of net load in the substation transformer; Details on the conclusions reached.

Investigates the degradation processes observed in the insulation from aged transformers. Description of the analysis of accelerated aged insulation samples; Performance of short term accelerated ageing experiments; Techniques used to examine the condition of aged insulation samples; Details on studies carried out on other electrical properties and pressboard samples; Indication of the results.

Describes the application of two diagnostic techniques for the determination of insulation condition in aged transformers. Details on the techniques; Investigation of other electrical properties of the cellulose polymer; Methodology used in the analysis of each technique; Discussion on the variation of the results through different locations in a power transformer.

Investigates the impacts of different three-phase transformer connections and load models on unbalance in power systems. Model derivation of grounded-wye-to-delta transformer; Application to three-phase optimal powerflow; Simulation of the three-phase transformer and load models; Conclusions.

Focuses on the losses calculation in the tie plate of the power transformer using the finite element method. Numerical method; Application; Conclusion.

The performance of the T and the \pi equivalent models used to represent transformers are tested under ferroresonance. Comparisons between simulations and laboratory experiments show the superiority of the \pi equivalent circuit. [ABSTRACT FROM AUTHOR]

The article presents abstracts on electronics and electrical topics which include the use of intelligent algorithm in detecting distributed generation, the diagnosis of faults in power transformer through finite element method and frequency response analysis, and the design, modeling and simulation of H-tree clock distribution networks.

Focuses on a study about the design of a largely self-calibratable voltage transformer testing set (VTTS). Description of the circuit for VTTS; Procedure for setting up the VTTS; Burden imposed on standard voltage transformers (VT).

In this letter, the ranges of furan content in oil in power transformers are predicted using measurements of oil tests, such as breakdown voltage, acidity, water content, and dissolved gas analysis. Predictive models based on machine-learning techniques are trained and tested to estimate the furan level. A prediction accuracy of 90% is achieved when using k-nearest neighbors as the classification model with a wrapper method as the feature selection technique. [ABSTRACT FROM PUBLISHER]

This study was designed to examine methanol as a new aging marker of insulating paper. An analytical GC-MS method coupled to headspace injection was developed, followed by a validation. To further validate the possible applicability of methanol for different transformer conditions some laboratory studies were performed such as a stability and an aging test. Oil samples of power transformers of several Belgian nuclear and coal-fired power plants have been analyzed since mid 2009 and are followed-up periodically to correlate the results with the analysis of the furanic compounds which have been used since mid 1980s as oil soluble degradation products of the insulating winding paper. It seemed that while no 2FAL was present some considerable amount of MeOH was detected which revealed some paper degradation. A second real case study was started to further correlate MeOH and 2FAL results. From these laboratory and real case studies it seemed that MeOH is a very promising marker for paper degradation in power transformers. [ABSTRACT FROM AUTHOR]

Wavelet network based approach for identification of fault characteristics of dynamic insulation failure during impulse test has been proposed. The network identifies the fault characteristics using the significant features extracted from cross-correlation sequence of winding currents of no-fault as well as impulse faulted winding insulation. The required winding current waveforms to extract significant features for identification of various fault characteristics are acquired by emulating different dynamic insulation failures in the analog model of 33 kV winding of 3 MVA transformer using developed analog fault simulator. The results show that the wavelet network using cross-correlation features has successfully identified the dynamic insulation failure characteristics, viz. fault type, condition and location of occurrence of failure along the length of the winding with acceptable accuracy. The efficacy of extracted features and developed wavelet network for fault characteristics identification is also compared with artificial neural network classifier. The concept of emulation of dynamic insulation failure, cross-correlation based feature extraction and wavelet based fault characteristics identification methods are explained. [ABSTRACT FROM AUTHOR]