transformer

Open Access Article

1 - Hierarchical Weighted Framework for Emotional Distress Detection using Personalized Affective Cues
Nagesh Jadhav

10.52547/jist.16499.10.38.89

Emotional distress detection has become a hot topic of research in recent years due to concerns related to mental health and complex nature distress identification. One of the challenging tasks is to use non-invasive technology to understand and detect emotional distres More

Emotional distress detection has become a hot topic of research in recent years due to concerns related to mental health and complex nature distress identification. One of the challenging tasks is to use non-invasive technology to understand and detect emotional distress in humans. Personalized affective cues provide a non-invasive approach considering visual, vocal, and verbal cues to recognize the affective state. In this paper, we are proposing a multimodal hierarchical weighted framework to recognize emotional distress. We are utilizing negative emotions to detect the unapparent behavior of the person. To capture facial cues, we have employed hybrid models consisting of a transfer learned residual network and CNN models. Extracted facial cue features are processed and fused at decision using a weighted approach. For audio cues, we employed two different models exploiting the LSTM and CNN capabilities fusing the results at the decision level. For textual cues, we used a BERT transformer to learn extracted features. We have proposed a novel decision level adaptive hierarchical weighted algorithm to fuse the results of the different modalities. The proposed algorithm has been used to detect the emotional distress of a person. Hence, we have proposed a novel algorithm for the detection of emotional distress based on visual, verbal, and vocal cues. Experiments on multiple datasets like FER2013, JAFFE, CK+, RAVDESS, TESS, ISEAR, Emotion Stimulus dataset, and Daily-Dialog dataset demonstrates the effectiveness and usability of the proposed architecture. Experiments on the enterface'05 dataset for distress detection has demonstrated significant results. Manuscript profile

Open Access Article

2 - Deep Transformer-based Representation for Text Chunking
Parsa Kavehzadeh Mohammad Mahdi Abdollah Pour Saeedeh Momtazi

10.61186/jist.19894.11.43.176

Text chunking is one of the basic tasks in natural language processing. Most proposed models in recent years were employed on chunking and other sequence labeling tasks simultaneously and they were mostly based on Recurrent Neural Networks (RNN) and Conditional Random F More

Text chunking is one of the basic tasks in natural language processing. Most proposed models in recent years were employed on chunking and other sequence labeling tasks simultaneously and they were mostly based on Recurrent Neural Networks (RNN) and Conditional Random Field (CRF). In this article, we use state-of-the-art transformer-based models in combination with CRF, Long Short-Term Memory (LSTM)-CRF as well as a simple dense layer to study the impact of different pre-trained models on the overall performance in text chunking. To this aim, we evaluate BERT, RoBERTa, Funnel Transformer, XLM, XLM-RoBERTa, BART, and GPT2 as candidates of contextualized models. Our experiments exhibit that all transformer-based models except GPT2 achieved close and high scores on text chunking. Due to the unique unidirectional architecture of GPT2, it shows a relatively poor performance on text chunking in comparison to other bidirectional transformer-based architectures. Our experiments also revealed that adding a LSTM layer to transformer-based models does not significantly improve the results since LSTM does not add additional features to assist the model to achieve more information from the input compared to the deep contextualized models. Manuscript profile

Open Access Article

3 - A Novel Wavelet Based Method for Improvement of Power Transformer Differential Relay against Magnetizing Inrush Current and CT Saturation
A. Rahmati M. Sanaye-Pasand

Differential protective relay serves as the main protection of transformers against faults in the windings for many years. Unremitting tries for more smart of this protection relay have been done by different creative manufactures and up to now different methods and inv More

Differential protective relay serves as the main protection of transformers against faults in the windings for many years. Unremitting tries for more smart of this protection relay have been done by different creative manufactures and up to now different methods and inventions have been proposed for better operational of the differential relay. However, a differential protection for differential currents would be handicapped by difficulties due to several natural phenomena which are the cause of false differential currents and misoperate of the relay. Some of these phenomena, such as the inrush current and saturation of instrument current transformers, are the main concern in designing an efficient differential protection algorithm. This paper at first, proposes a new algorithm based on the Wavelet Transform (WT) to identify internal fault from magnetizing inrush in three phase power transformers. The internal faults can be accurately discriminated from inrush current less than a quarter a cycle after the disturbance. At following with definition of an index which it is extracted from the high frequencies by WT, the restrain current in bias-current characteristic of differential relay has been improved. Obtained results demonstrate that the proposed algorithm can provide the desired response and can be used as a very fast and accurate method. Manuscript profile

Open Access Article

4 - Determination of a New Model for Investigating Ultra-Saturation Phenomenon during the Enegization of the Loaded Three-Phase Power Transformer and Its Effect on Differential Protection
B. Noshad M. Razaz S. Gh. Seifossadat

One of the mal-operation of the power transformer differential protection that may occur during the energization of a loaded power transformer is the ultra-saturation phenomenon. In this paper, a new model to study the ultra-saturation phenomenon during the energizaton More

One of the mal-operation of the power transformer differential protection that may occur during the energization of a loaded power transformer is the ultra-saturation phenomenon. In this paper, a new model to study the ultra-saturation phenomenon during the energizaton of a loaded three-phase power transformer is presented and its effect on the differential protection of the power transformer is considered. For modeling of the ultra-saturation phenomenon, the nonlinear characteristic of the transformer core and the saturation effect of current transformers are considered. It is assumed that the load of the power transformer is a resistive and an inductive load. The mal-operation of the differential protection depends on a variety of factors the most important parameters of which are inception angle and residual flux. In this paper the parameters mentioned will study in different cases. In this paper, simulation is done by MATLAB program. Manuscript profile

Open Access Article

5 - 3D Finite Element Analysis of MV Three-Phase Transformer Mechanical Forces Effected by Inrush Current Based on a Novel Winding Structure
A. Nasiri A. Ranjbar F. Faghihi S. Soleymani

Transient mechanical force in transformer induced critical mechanical stress on windings and transformers in radial and axial directions. In this paper, impact of force’s within transient inrush current duration on MV three phase transformer with propose novelty windin More

Transient mechanical force in transformer induced critical mechanical stress on windings and transformers in radial and axial directions. In this paper, impact of force’s within transient inrush current duration on MV three phase transformer with propose novelty winding configuration (S-P-S) to considered. In order to forces analysis, a 3-D model of three phase transformer developed by use Ansoft Maxwell V15.0. Magnetic vector potential, Magnetic flux density and electro-mechanical force’s of SPS-type and conventional-type of configuration windings and transformer calculated from a 3D finite element model. Based on the comparison and result analysis, proposed an optimal configuration for transformer winding in order to trade-off and minimization of electromechanical force’s in the transient inrush current state. Manuscript profile

Open Access Article

6 - Winding Losses Calculation in Multi-Winding Traction Transformer Using a Semi-Numerical Method
D. Azizian G. Gharehpetian

Nowadays, multi-winding transformers are widely used in power systems, especially in traction networks and steel producing companies. The multi-winding transformers have special geometry. They encounter with serious problems and difficulties in design procedure in compa More

Nowadays, multi-winding transformers are widely used in power systems, especially in traction networks and steel producing companies. The multi-winding transformers have special geometry. They encounter with serious problems and difficulties in design procedure in comparison with conventional two-winding transformers. Considering the importance of windings losses (and the generated heat), the current research firstly focuses on thermal calculations in this type of transformers, also introduces a semi-numerical technique for electromagnetic analysis of split-winding traction system transformer. Combining finite element and analytical methods, the windings losses distribution due to eddy currents is calculated and the modeling results are validated using the experimental results. As shown, the introduced semi-numerical method is a powerful technique for electromagnetic modeling and winding losses calculations in split-winding transformers. Also, the winding losses of the split-winding transformer are discussed and compared to the conventional two-winding transformer results. Finally, the relation between the winding losses and frequency is studied in this paper. Manuscript profile

Open Access Article

7 - Lifetime Estimation of Distribution Transformers in Present of Harmonic Loads: Case Study of Ilam Distribution Transformers
A. Moradkhani M. H. Parhizgari D. Bagheri

One of the main components of distribution systems is transformer, and their failure will cause irreparable damage in power systems and distribution companies. These failures are to increase the losses of the transformers due to the increase of harmonics, especially the More

One of the main components of distribution systems is transformer, and their failure will cause irreparable damage in power systems and distribution companies. These failures are to increase the losses of the transformers due to the increase of harmonics, especially the current harmonics. These losses increase the temperature of transformers and reduced the lifetime of distribution transformers. In this paper evaluated losses and lifetime in the presence of harmonic loads in Ilam distribution transformers. Technical and practical assessments of the presence of harmonic loads and their effect on the lifetime of transformers have been investigated. According to the obtained results the useful lifetime of some transformers from 30 years to 17 years are decreased. Manuscript profile

Open Access Article

8 - A Model-Based Approach for Improving Power Transformer Differential Protection
Zahra Kazemi Mohammad Mohammadpour E. Farjah

In this paper, a new algorithm based on Kalman Filter (KF) is proposed for improving the reliability of power transformer differential protection. The three-phase currents of the transformer at the energization side are first estimated by KF. Three residual signals whic More

In this paper, a new algorithm based on Kalman Filter (KF) is proposed for improving the reliability of power transformer differential protection. The three-phase currents of the transformer at the energization side are first estimated by KF. Three residual signals which are the differences between the measured (by current transformers) and estimated (by KF) are defined and considered as the decision criteria to discriminate the fault and inrush conditions. During the transformer energization, the residual signals are almost zero. However, in fault conditions, the residual signals exceed a determined threshold value and a trip command will be subsequently issued. The performance of the proposed method is verified using simulations in MATLAB and PSCAD software. Manuscript profile

Open Access Article

9 - A Thermal Equivalent Circuit for Thermal Analysis of Power Transformers under Harmonic Loads
m. mikhak B. Rezaeealam m. jafarboland v. ebrahimian m. asgari

The majority of the power transformers failures are caused by the thermal stresses under abnormal operating conditions, such as harmonic loads. Therefore, it is of great interest to determine the temperature distribution inside the power transformers. In this paper, a n More

The majority of the power transformers failures are caused by the thermal stresses under abnormal operating conditions, such as harmonic loads. Therefore, it is of great interest to determine the temperature distribution inside the power transformers. In this paper, a new thermal equivalent circuit is presented by which the temperature in different regions of the transformer is estimated under harmonic loads. Also, the three-dimensional Finite Element (FE) Model of the power transformer is developed to calculate the power losses in each part of the transformer that are considered as the heat sources in the proposed equivalent circuit. The computed hotspot and average oil temperatures are compared with those obtained from IEEE Std C57.91 method, thereby the accuracy of the proposed method for calculating the temperature rise due to harmonic loads, is investigated. Finally, derating of the power transformer is discussed under harmonic loads. Manuscript profile

Open Access Article

10 - Evaluation of the Effect of Transformer Oil Parameters on the Transformer Health Index Using Curve Estimation Method
Morteza Saeid Hamed Zeinoddini-Meymand

Transformers are one of the most expensive and important equipment in power systems that are under the influence of electrical, thermal and chemical reactions The transformer health index is a standard that is used to evaluate the condition and determine the remaining l More

Transformers are one of the most expensive and important equipment in power systems that are under the influence of electrical, thermal and chemical reactions The transformer health index is a standard that is used to evaluate the condition and determine the remaining life of the transformer by using laboratory data and field inspections. The purpose of this article is to determine the relationships between electrical, physical, chemical parameters of oil, dissolved gases in oil and transformer health index. One of the advantages of using the regression method in the analysis of transformer data compared to other methods for determining the transformer health index is determining the influence of the parameters that have the greatest impact on each other. In this article, Curve Estimation Regression method is used and the results are drawn by drawing graphs by SPSS statistical software to analyze the parameters. To carry out the simulations, the laboratory data of some transformers have been considered. Manuscript profile

Open Access Article

11 - Integrated Modeling of Bidirectional Solid-State Transformers: Rectifier, DC to DC Converter and Inverter Stages
hamed molla-ahmadian morteza shafiei javid khorasani

: One of the new and growing equipment in modern power networks is solid state or power electronic transformer. These types of transformers are based on power semiconductor switches and high frequency transformers. Compared to traditional transformers, it has several ca More

: One of the new and growing equipment in modern power networks is solid state or power electronic transformer. These types of transformers are based on power semiconductor switches and high frequency transformers. Compared to traditional transformers, it has several capabilities such as the ability to operate with input voltage variations in amplitude and frequency, automatic regulation of output voltage and input power factor correction. The investigated transformer has the ability to transfer power in both directions and has three stages, including the rectifier, the middle stage and the inverter stage. This transformer has a large number of semiconductor switches and its modeling, analysis, design and simulation is difficult and complex. In particular, real-time simulation of these transformers with conventional models is not possible. In these cases, the use of averaging theory seems to be the appropriate solution. In this paper, the averaging theory is applied to a solid-state transformer and its modeling is done in a simple and powerful way with the ability to study real-time, transient and steady states performance. The proposed modeling includes differential equations and equivalent circuits and offers an integrated transformer model with the ability to study the interaction between stages as a part of power system. The presented models are used in simulation of smart grids, DC microgrids and connection of distributed generation sources to the grid, as well as analysis and design of solid-state transformer behavior in areas such as renewable energies and electrical transportation. In addition to the proposed modeling, the closed-loop control structure has been implemented for all three stages. Transformer simulation is performed by implementing differential equations in SIMULINK/MATLAB software and verified the proposed model. Manuscript profile

Open Access Article

12 - Investigating the three-phase to five-phase time converter using a special transformer connection
Ali Bahadran Seyed Majid Keshavarz

The first five-phase induction motor drive systems were proposed in the late 1970s for variable speed drive applications. Since then, considerable research efforts have been devoted to identifying the development of commercially feasible multiphase propulsion systems. S More

The first five-phase induction motor drive systems were proposed in the late 1970s for variable speed drive applications. Since then, considerable research efforts have been devoted to identifying the development of commercially feasible multiphase propulsion systems. Since the three-phase supply is available from the network, it is necessary to remove a static phase conversion system to obtain a multi-phase supply from the existing three-phase supply. Therefore, this paper presents a new transformer connection scheme to convert a three-phase network power supply into a five-phase constant voltage and constant frequency supply. The proposed transformer connection gives a five-phase output and therefore, can be used in applications that require a five-phase power supply. Currently, the five-phase motor drive is commercially viable. The five-phase transmission system solution can be further explored as an efficient solution for bulk power transmission. The connection scheme is explained using simulation and experimental approach to prove the feasibility. The geometry of the manufactured transformer is explained in this article. Manuscript profile

Open Access Article

13 - Investigating the performance of electronic transformers on the environment
Maziar Demory Nejad Mehrdad Mohadpur

During the last 30 and 40 years, TS transformer substations have evolved a lot, from the classic assembly in open areas, partition walls and outdoors, to the existing model, in order to increase human safety and material reliability, as well as significant progress. Ass More

During the last 30 and 40 years, TS transformer substations have evolved a lot, from the classic assembly in open areas, partition walls and outdoors, to the existing model, in order to increase human safety and material reliability, as well as significant progress. Assembly and space reduction, new results such as metal enclosures, prefabricated buildings, compact transformer substations and finally installed substations are also revolutionary. Due to society's increasing concern about the environment, the industry as a whole is rethinking the design and materials that may mean pollution, trying to replace them as much as possible with environmentally friendly communities. The inevitable development of society cannot and should not destroy the future of the earth. The time for sustainable development has come. So our work here today is a help in that sense. Manuscript profile

Open Access Article

14 - Performance Improvement of High Voltage Transformer in Klystron Amplifier Power Supply by Magnetizing Current Balancing
Abolfazl Nasiri mohsen ganji seed mohamad Alavi

<p class="Abstract">In this research, the structure of a Full-bridge converter has been used to feed the klystron amplifier. Three Full-bridge transducer modules with high voltage transformers are used to supply the power of klystron (100 kW, 4 kV, 25 kV). The output of More

<p class="Abstract">In this research, the structure of a Full-bridge converter has been used to feed the klystron amplifier. Three Full-bridge transducer modules with high voltage transformers are used to supply the power of klystron (100 kW, 4 kV, 25 kV). The output of the transformers is rectifier in a star structure and after passing through a π filter, the circuit of the klystron lamp is supplied. The output of the power supply is 1 ms width and frequency of repetition is 50 Hz. The input voltage of the converter is 500 VDC, which is supplied by a three-phase feed. In this research, by balancing the magnetizing current of high frequency transformers, the maximum magnetization current of transformers decreases and decreases the maximum current of transistors. In addition, the core dimensions of the transformer decrease by reducing the maximum magnetization current. As a result, the dimensions, volume, and weight of the klystron drive circuit are reduced. Also, by using leakage inductance of high frequency transformer, series resonance circuit has been created and soft switching conditions have been provided. In this way, it improves the performance of the klystron driven circuit. Modulator performance has been simulated and approved using PSCAD software and resistive load.</p> Manuscript profile

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