Transformer Connections Research Articles

Kutafuta Maisha: Connections Between Agency and Structure in Makonde Migratory Labour from Mozambique to Tanzania (ca. 1907-1964)

The drive for making colonial territories “profitable” through various means, such as commodity extraction, got entangled with complex events that stood well beyond the intervening capacity of colonial administrators, and labour migration was no exception. This article analyses Makonde migration from Northern Mozambique toward sisal plantations in neighbouring British Tanganyika during the twentieth century and argues that the interweaving of written and oral sources renders two contrasting pictures: one of an orderly planned commodity sector mediated by industrial pundits and sustained by a rhetoric of colonial “development”; and another of spontaneous, haphazard yet rational life decisions undertaken by migrant men and women. We challenge the conventional take on African labour migration by discussing a much more complex picture that shows how the colonial labour migration system had to address the migrants’ needs and how migrants successfully subverted coercive structures for their benefit, and by doing so, Makonde migrants established their own transformative connections with global phenomena that outreached their participation in commodity production chains

Breathing together: Needed relationships and complex selfobjects

ABSTRACT In this paper the author extends his metatheory of needed relationships to posit a more complex form of selfobject connection than has been previously theorized. He argues that there are degrees of selfobject connectedness and that for the fullest, most transformative connection to be actualized certain conditions in the patient’s experience of the analyst need to be met. The co-creation of such conditions amounts to a new needed relationship—a transformational intersubjective medium—uniquely co-created and unpredictably emergent within each analytic dyad, which somehow comes to address a traumatic relational breach in the original parent-child field and restores an ethic of care, lawfulness, competence and love that was the patient’s original birthright. This amounts to a fully relational self psychology, but a more forward edge relationality than that of mainstream Relational theory, which, at least historically, has placed more emphasis on repetition and enactment than on what the author calls the needed relationship.

Three-Level Secure Smart Protection for Ring Grid-Connected Distributed Generation

The penetration increase in distributed generators (DGs) into smart grids (SGs) will lead to new challenges, especially in protection systems. In the case of ring grids, the behavior of the short-circuit current is affected by DGs, and the medium voltage (MV) transformer connections significantly influence the changes; therefore, the protection strategies must be adapted for these scenarios. This study provides a comprehensive protection system for the MV distribution system (DS), including reconfigurable smart ring grids. The proposed protection methods contain three protection algorithms. The first protection algorithm relies on communication among all protective devices (PDs) in the grid, whereas the second protection method uses communication among PDs along the same line. Then, a third algorithm built on the local data of each PD is suggested as a backup to prevent communication issues and offer more reliable protection. MATLABTM SIMULINK simulations and experimental results on a scalable hardware grid were also employed to validate the protection algorithms.

Transformer Connections: Improving Segmentation in Blurred Near‐Infrared Blood Vessel Image in Different Depth

AbstractHigh‐fidelity segmentation of blood vessels plays a pivotal role in numerous biomedical applications, such as injection assistance, cancer detection, various surgeries, and vein authentication. Near‐infrared (NIR) transillumination imaging is an effective and safe method to visualize the subcutaneous blood vessel network. However, such images are severely blurred because of the light scattering in body tissues. Inspired by the Vision Transformer model, this paper proposes a novel deep learning network known as transformer connection (TRC)‐Unet to capture global blurred and local clear correlations while using multi‐layer attention. Our method mainly consists of two blocks, thereby aiming to remap skip connection information flow and fuse different domain features. Specifically, the TRC extracts global blurred information from multiple layers and suppresses scattering to increase the clarity of vessel features. Transformer feature fusion eliminates the domain gap between the highly semantic feature maps of the convolutional neural network backbone and the adaptive self‐attention maps of TRCs. Benefiting from the long‐range dependencies of transformers, we achieved competitive results in relation to various competing methods on different data sets, including retinal vessel segmentation, simulated blur image segmentation, and real NIR blood vessel image segmentation. Moreover, our method remarkably improved the segmentation results of simulated blur image data sets and a real NIR vessel image data set. The quantitative results of ablation studies and visualizations are also reported to demonstrate the superiority of the TRC‐Unet design. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Adaptive convergence enhancement strategies for Newton–Raphson power flow solutions in distribution networks

AbstractThis study introduces a series of strategies to enhance convergence in the Newton–Raphson power flow method for unbalanced distribution networks. The proposed approach incorporates graph theory, Kron reduction, and current injection techniques. The network components, including transmission conductors, power transformers, power conductors, shunt capacitors/reactors, and demand loads, were merged into the bus impedance matrix. Using two identification processes (based on mismatches for bus voltages and bus power injections) and optimal multipliers (μ), the proposed approach estimates the initial bus voltages by approximating the converged solutions. To verify the effectiveness of the proposed approach, the authors performed a comparative analysis of five IEEE test feeders in various scenarios. The results confirmed the effectiveness of the proposed approach, particularly for unbalanced distribution systems with diverse transformer connections.

Comparison, Simulation and Analytical Investigation of Voltages, Currents and Powers Waveforms of the at Sixteen Different Combination Step-Down Three Phase Transformer Connections

This article investigates different currents, voltages, phase differences and powers of sixteen different connections step-down three phase connections transformers fed sinusoidally for analytical and simulation conditions. In this paper, analytical modeling and equations for step-down three phase transformer based on current point signal and voltage polarity are presented. A discussion based on their theoretical use is then presented in the simulation along with calculations regarding their power performances. Results obtained from simulations and analytical situations of sources, transformer primary, transformer secondaries and loads currents (A), voltages (V), powers (W), between sources and transformer primary, between transformer primary and transformer secondaries and between transformer secondaries and loads phase differences were also obtained. These models are also validated by simulation results of currents, voltages, phase differences and powers waveforms for each analytical case. PSpice program is used for this simulation.

Transformative Peer Connections: Early Experiences From the ASCO Palliative Care Community of Practice.

The integration of palliative care into routine oncology practice is the standard of care by most leading cancer organizations. Palliative medicine helps to deliver higher quality of care at a lower cost. However, there are barriers to implementing palliative oncology at many institutions for myriad reasons. In this article, we discuss an innovative strategy that ASCO implemented called the Communities of Practice (CoP). We share our experiences as the Palliative Care CoP and how our group seeks to develop processes and structures to collectively promote systemic change and enhance palliative care delivery for people with cancer. Our Palliative Care CoP engages with senior leaders, administrators, and those in power to achieve a shared vision of delivering holistic health care for people with serious illness. We continue to evolve to meet our members' growing needs by addressing eight main domains: (1) increasing palliative care education and resources; (2) creating opportunities for global palliative care research; (3) providing peer mentorship and community building; (4) engaging with patient advocates; (5) supporting and developing interdisciplinary teams; (6) assisting with professional development and identity formation, especially for trainees and early career faculty; (7) extending our outreach through social media; and (8) enhancing the clinical practice of palliative oncology. The ASCO CoP has been a vital forum to realize ASCO's mission of conquering cancer and advancing the Art and Science of Cancer Care: From Comfort to Cure.

Introducing costumatics: Costume’s transformative connection between actor and character

Introducing costumatics: Costume’s transformative connection between actor and character

Multi-modular bridge-type FCL for enhancing FRT capability of VSC-HVDC connected offshore wind plants during AC faults

This paper presents a novel concept Multi-Modular Bridge-Type Fault Current Limiter (MMBFCL) for enhancing the fault ride-through (FRT) capability in Voltage Source Converter (VSC)-based High-Voltage Direct-Current (HVDC) systems. The MMBFCL can be directly connected to HVDC system in ac grid side without series connection of semiconductor switches and series injection transformers. Also, the limiting resistor of each module is determined based on binary arrangements to provide a multi-step insertion resistor BFCL to limit the fault current and enhance the FRT capability under different voltage sag levels. The principle operation and control system of the MMBFCL is described. Then, the performance of the MMBFCL for enhancing the FRT is validated through time domain simulations by PSCAD/EMTDC software in a HVDC integrated wind farm system. Also, the performance of the MMBFCL is compared with the single-modular BFCL (SMBFCL). Simulation results reveal that the MMBFCL compensate the voltage sag for each voltage sag levels without any over voltage at the HVDC terminal. Also, it has superior performance than SMBFCL.

Field Programmable Gate Array-Based Smart Switch to Avoid Inrush Current in PV Installations.

This paper introduces an FPGA-based implementation of a smart switch designed to avoid inrush currents occurring during the connection of single-phase transformers utilized in grid-connected photovoltaic (PV) systems. The magnitude of inrush currents is notably impacted by the residual flux within the transformer core and the precise moment of energization relative to the wave cycle. Alternative methods frequently hinge on intricate procedures to estimate residual flux. This challenge is adeptly circumvented by the innovative smart control system proposed herein, rendering it a cost-effective solution for grid-connected PV systems. The proposed solution for mitigating inrush current remains effective, even in the face of challenges with current and voltage sensors. This resilience arises from the system's ability to learn and adapt by leveraging information acquired from the network.

АЛГОРИТМ ПРИМЕНЕНИЯ ДВУХ ТРАНСФОРМАТОРОВ ВЗАМЕН ОДНОГО НА ТРАНСФОРМАТОРНЫХ ПОДСТАНЦИЯХ 10/0,4 КВ

According to statistics, losses in electrical networks of power supply organizations in the Russian Federation amount to 10 percent, while the world average is 8 percent. The Energy Strategy for the period until 2035, approved by the Government of the Russian Federation in 2020, sets the goal of achieving a reduction in electrical energy losses to 7.3 percent by 2035. One of the effective ways to reduce electricity losses is to replace underloaded transformers at substations in order to increase the transformer load factor. For this purpose, a method was developed for using two transformers instead of one at 10/0.4 kilovolt transformer substations. (Research purpose) is to develop an algorithm for implementing a method of using two transformers instead of one at 10/0.4 kilovolt transformer substations in order to reduce electricity losses. (Materials and methods) General scientific research methods, methods for constructing algorithms, control and data transmission systems, and analysis of scientific and technical information were used as the methodological basis for the research. (Results and discussion) This paper presents an algorithm for implementing the method of using two transformers instead of one at 10/0.4 kilovolt transformer substations. The algorithm allows automatically controlling the connection and disconnection of power transformers at a transformer substation depending on their load and season, while recording these actions and sending the corresponding signals to the dispatcher of the power supply organization. (Conclusions) Based on the results of the study, it was found that the developed algorithm for implementing the method of using two transformers instead of one at 10/0.4 kilovolt transformer substations makes it possible to achieve a reduction in electricity losses by increasing the load factor of transformers.

Allocation of Dynamic Operating Envelopes in Distribution Networks: Technical and Equitable Perspectives

A Dynamic Operating Envelope (DOE) specifies the available capacity to import/export power for Distributed Energy Resources (DERs) or connection points of a distribution network in a time interval without violating its physical and operational constraints. This paper proposes a two-stage, top-down approach to allocate DOEs in MV-LV (medium voltage-low voltage) integrated distribution networks. In the first stage, Distribution System State Estimation (DSSE) and Capacity Constrained State Optimisation (CCSO) techniques are employed to allocate DOEs at transformer connection points. Using network data from available metering infrastructure, DSSE estimates the current operational state of the network, whereas CCSO facilitates the DOE allocations at transformer connection points considering technical, soft-equitable and equitable perspectives. In the second stage, the allocated DOEs, containing available aggregate export/import power, are distributed among DERs of LV networks ensuring network integrity. Real-world data of an Australian MV-LV network is employed to demonstrate the effectiveness of proposed approach. Test results show that technical perspective can offer maximum allocated export/import power, whereas, minimum disparity of allocated power among different connection-points is attained for equitable perspective. Further, insightful performance studies of DOE and existing fixed export policies are conducted considering the condition of present as well as future power systems expecting substantial proliferations of renewables.

Feminist Transformation: Result of the Waves of Feminist Movement

This article is about feminist transformation. The main objective is to draw the connection of feminist transformation to waves and types of feminism. Document analysis has conducted under qualitative research design for drawing conclusion. The main intention of feminist transformation is to eradicate various forms of oppression and injustice that exist on the basis of gender difference. The right to vote and property ownership, legal and social rights and the use of social media for ending oppression were the achievement of the waves and these achievements were for feminist transformation. On the other hand, all feminism types have the same motive to end oppression on the basis of gender which makes feminist transformation easier. It is concluded that there is the means-end relationship between waves and types of feminism to feminist transformation. The saying and doing of people and authority must be same for true feminist transformation.

Investigation of the usage of zigzag transformers to reduce harmonics distortion in distribution systems

The increasing use of power electronics in various sectors leads to harmonic distortion in electric power systems, affecting power quality and equipment longevity. While harmonic filters have been used to address this issue, they are limited in effectiveness, particularly in reducing distortion across the entire distribution system. This study aims to reduce harmonic distortion using a zigzag transformer as a more comprehensive solution in mitigating harmonic distortion throughout the entire distribution system. In this research, the zigzag transformer was placed at point common coupling to reduce harmonic distortion in the distribution system as a whole. A zigzag transformer connection was configured by connecting either three windings of a single-phase transformer or one winding of a three-phase transformer. Based on the results of this research, the total harmonic distortion (THD) value has decreased from 25.26 % to 2.48 % following the implementation of the zigzag transformer. This substantial decrease in THD concludes the zigzag transformer's effectiveness as a solution for improving power quality in electrical distribution systems.

Exploring the interdependence between control and protection philosophies in inverter integrated power system: A case study on directional relaying schemes

The potential impacts of the inverter-interfaced renewable energy resources (IIRERs) on the performance of sequence-based directional relaying schemes (SBDRS) have been investigated in this paper. The directional overcurrent relays such as 67POS, 67NEG, 67ZERO and 32Q have been considered for the investigation. CIGRE-14 bus system with IIRERs along with detailed modeling of inverter control scheme (with and without grid codes) and SBDRS have been done in the PSCAD environment. The mathematical analysis and circuit realization of the IIRERs have been attempted in the paper. The exclusive fault characteristics exhibited by IIRERs cause the conventional SBDRS to mal-operate. Significant change in levels of sequence currents and angular relationships between sequence voltages and currents during faults contributes to relay's unpredictable behavior. The comparative study based on different fault types, fault resistances and interconnecting transformer connections have also been done. The study reveals the impact of non-generalized angular differences between positive sequence voltage and current at the inverter terminal on performance of 67POS. It is found that 67NEG and 32Q mal-operated for all types of unbalanced faults while the 67ZERO can be utilized for grounded fault with delta-star grounded connection of interconnecting transformer.

Smart Switching in Single-Phase Grid-Connected Photovoltaic Power Systems for Inrush Current Elimination

Grid-connected photovoltaic (PV) power systems are one of the most promising technologies to address growing energy demand and ecological challenges. This paper proposes smart switching to mitigate inrush currents during the connection of single-phase transformers used in PV systems. An effective inrush current mitigation contributes to the reliability of PV systems. The inrush current severity is influenced by the pseudorandom residual flux at the transformer core and the energization point-on-wave. The most common approach to avoid inrush currents is controlled connection, which requires prior knowledge of the residual flux. However, the residual flux can differ in each case, and its measurement or estimation can be impractical. The proposed smart switching is based on a comprehensive analysis of the residual flux and the de-energization trajectories, and only requires two pieces of data (ϕRM and ϕ0, flux values of the static and dynamic loops when the respective currents are null), calculated from two simple no-load tests. It has a clear advantage over common approaches: no need to estimate or measure the residual flux before each connection, avoiding the need for expensive equipment or complex setups. Smart switching can be easily implemented in practical settings, as it considers different circuit breakers with distinctive aperture features, making it cost-effective for PV systems.

Out the Gate: Towards a Rhizomatic Understanding of Methamphetamine Use in Aotearoa-New Zealand

As part of an interview-based qualitative study on the life-course of people who formally used methamphetamine in Aotearoa-New Zealand, this paper uses Deleuze and Guattari's rhizomatic perspective to trace the specific effects and particular relations involved in methamphetamine use. The methamphetamine-using trajectory for the 42 former users is a multifaceted and constantly fluctuating process involving multiple entries, exists, pathways, and restarts. By amplifying and enlightening the user, methamphetamine use begins by liberating desire through sending the user “out the gate,” but long-term high-dose use can end up constraining and repressing subjectivity and cyclically producing adverse psychological, emotional, interpersonal, and social effects. As a metamorphic process that produces transformative change, long-term high-dose methamphetamine use is a nonlinear rollercoaster ride that typically leads to a downward spiral whereby life stagnates, shrinks, or regresses. By undermining productive and transformative connections, the life of the long-term high-dose methamphetamine user typically—but not inevitably—involves revolving instead of evolving. Against a linear and deterministic popular media-generated narrative about methamphetamine use, a rhizomatic perspective emphasizes the potential for transformation by focusing upon the situational and interactional processes involved in users who undergo complex and varied temporary changes. From Deleuze and Guattari's perspective, disentangling from long-term high-dose methamphetamine use requires activating new relationships and possibilities for desire by forming meaningful biopsychosocial connections.

A New Control Strategy of Hybrid Reactive Power Compensation System in Distribution Network

Reactive power compensation is an important measure to improve the power quality of distribution networks, especially with the increasing connection of distribution transformers, heavy industrial electrical equipment, and asynchronous motors, which generate a large amount of reactive power demand. Traditional reactive power compensation devices, such as fixed capacitors (FC) and thyristor switched capacitors (TSC), have some drawbacks, such as low response speed, harmonic generation, and switching shock. A static synchronous compensator (STATCOM) is a flexible AC transmission system (FACTS) device that can provide fast and continuous reactive power compensation, but it also has some limitations, such as high cost, large capacity requirement, and low utilization rate. Therefore, hybrid reactive power compensation systems that combine FC or TSC with STATCOM have attracted much attention in recent years. Many researchers have proposed and studied different topologies and control methods of hybrid systems to overcome the disadvantages of single devices and achieve better performance. However, most of the existing hybrid systems are designed for low or medium-voltage distribution networks, and their performance under high-voltage distribution networks is still unclear. Moreover, the coordination control strategy of the hybrid system and its subsystems is also a key issue that affects the effectiveness and efficiency of reactive power compensation. In view of this, this paper aims to propose a TSC+STATCOM hybrid reactive power compensation system for high-voltage distribution networks, which optimizes the shortcomings of traditional reactive power compensation devices. The system uses the synergistic effect of TSC and STATCOM to achieve large-scale static reactive power and small-scale dynamic reactive power compensation and adopts a switching strategy based on an expert decision system. This paper introduces the working principle of each subsystem of the hybrid reactive power compensation system in detail and builds a simulation model of the hybrid reactive power compensation system under a high voltage distribution network on Matlab/Simulink platform. The simulation results verify the feasibility and excellent performance of the system control method in reactive power compensation and improving power quality.

Development of a three‐phase power‐flow calculation method for distribution systems with automatic handling of arbitrary winding connections of transformers

AbstractSingle‐phase loads and photovoltaic generation cause three‐phase imbalance in distribution systems, and prospective growth of normal chargers of electric vehicles may even increase the imbalance. The analysis of such unbalanced systems requires the three‐phase power‐flow calculation. Since existing methods require the admittance matrices of three‐phase transformers, they must be derived for all possible winding connection patterns in advance to its computer‐code implementation. This paper proposes a three‐phase power‐flow calculation method which formulates circuit equations using the modified nodal analysis, making it possible to automatically handle any winding connection. The power‐flow constraints are then embedded into the circuit equations using a fixed‐point iteration. Newton‐Raphson, backward/forward sweep and fixed‐point iteration methods are the existing three categories of solution methods. Newton‐Raphson methods may show convergence problems due to the high R/X ratios of distribution lines. Backward/forward sweep methods cannot be used, because loops are temporarily formed in a distribution system during circuit switching. These justify the use of a fixed‐point iteration. In this paper, the proposed method is validated by practical examples.

Reduction of geomagnetically induced current impacts by optimized neutral point connections

AbstractSolar storms impact electrical power grids by causing quasi‐DC neutral point currents in transformers. These currents lead to half‐cycle saturation as well as other related and unwanted effects in the grid. To reduce the effect of these currents on the grid, DC‐blocking devices can be installed or changes in the grid topology can be made. However, these counter measures often have unwanted side effects or cannot be applied to the grid due to operational restrictions. In this work, a novel mitigation approach, based on the distribution of currents on more transformers, is presented. The number and location of grounded transformer neutral points is optimized, taking grid related constraints such as the minimal number of transformer connections into account. It is shown that the algorithm can effectively reduce the stress on transformers without any additional assets and thus increase system security.