scholarly journals To the Problem of Protection of Medium Voltage Instrument Transformers with Fuses: Analytical Research

2021 ◽  
Vol 60 (3) ◽  
pp. 92-102
Author(s):  
Yevgen Bajda ◽  
Oleksandr Grechko ◽  
Viktor Buhaichuk ◽  
Robert Knápek
Keyword(s):  
Analytical Study ◽  
Promising Direction ◽  
Medium Voltage ◽  
Advantages And Disadvantages ◽  
Instrument Transformers ◽  
Effective Level ◽  
Instrument Transformer ◽  
Analytical Research ◽  
Further Development

Introduction. In the medium voltage power grid of 6–35 kV, there is a problem of protecting voltage instrument transformers. This is due to the insufficiently effective level of their protection with fuses. Recently, there have been more and more reports of accidents associated with the failure of voltage instrument transformers not only in Ukraine, but also abroad. The issue of conducting an analytical study of the problem of protection of medium voltage instrument transformers by fuses is relevant. Goal. Investigation of designs and characteristics of fuses for medium voltage instrument transformers to improve the efficiency of their protection. Results. The article shows that protection of medium voltage instrument transformers with epoxy insulation is often provided by fuses, in which the nominal current of the fuse-link is significantly higher than the maximum permissible long-term current of the primary winding of the instrument transformer. A comparative analysis of the current values of the primary winding of medium voltage instrument transformers with the values of the rated currents of the fuse-links of fuses of various manufacturers presented on the Ukrainian market is carried out. The design features and technical characteristics of fuses for medium voltage instrument transformers have been investigated in order to increase the efficiency of their protection. The advantages and disadvantages of the designs of fuses from various manufacturers have been investigated and it has been established that the design of fuses requires further improvement in order to increase the efficiency of protection of medium voltage instrument transformers. Discussion and prospects for further development. Since in Ukraine, the need for fuses to protect medium voltage instrument transformers is provided mainly by supplies abroad, a promising direction for further development in this direction is the creation of a domestic competitive design of a fuse and its introduction into production.

scholarly journals On single pole instrument voltage transformer overheating

2021 ◽  
Vol 72 (1) ◽  
pp. 29-34
Author(s):  
František Janíček ◽  
Lukáš Český ◽  
Filip Skudřík
Keyword(s):  
The State ◽  
Voltage Transformer ◽  
Output State ◽  
Medium Voltage ◽  
Instrument Transformers ◽  
Nominal Voltage ◽  
Instrument Transformer

Abstract The paper deals with calculation of overheating of a voltage instrument transformer used in medium voltage substations. Calculation of the primary and secondary windings is compared with measured values. These values are evaluated according to IEC 618691:2007, IEC 61869-3:2011 and IEC 60085:2007. In evaluation we focused on the state 1.9 × nominal voltage and thermal limiting output state. The article also compares the results for various parameters of instrument transformers that are necessary for clarification of calculation.

Problems of Distance Education

2018 ◽  
Vol 7 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Rostislav Fojtík
Keyword(s):  
Distance Education ◽  
Distance Learning ◽  
Computer Science ◽  
Full Time ◽  
Advantages And Disadvantages ◽  
E Learning ◽  
Educational Requirements

Abstract Distance learning and e-learning have significantly developed in recent years. It is also due to changing educational requirements, especially for adults. The article aims to show the advantages and disadvantages of distance learning. Examples of the 20-year use of the distance learning form of computer science describe the difficulties associated with the implementation and implementation of this form of teaching. The results of students in the full-time and distance form of teaching in the bachelor’s study of computer science are compared. Long-term findings show that distant students have significantly lower scores in the first years of study than full-time bachelor students. In the following years of study, the differences diminish, and students’ results are comparable. The article describes the possibilities of improving the quality of distance learning.

scholarly journals New Sensor for Medium- and High-Voltage Measurement

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4654
Author(s):  
Andrzej Wetula ◽  
Andrzej Bień ◽  
Mrunal Parekh
Keyword(s):  
Finite Element Method ◽  
Electronic Devices ◽  
Finite Element Method Simulation ◽  
Laboratory Model ◽  
Power Electronic ◽  
Proof Of Concept ◽  
Voltage Measurement ◽  
Medium Voltage ◽  
Narrow Frequency Band ◽  
Further Development

Measurements of medium and high voltages in a power grid are normally performed with large and bulky voltage transformers or capacitive dividers. Besides installation problems, these devices operate in a relatively narrow frequency band, which limits their usability in modern systems that are saturated with power electronic devices. A sensor that can be installed directly on a wire and can operate without a galvanic connection to the ground may be used as an alternative voltage measurement device. This type of voltage sensor can complement current sensors installed on a wire, forming a complete power acquisition system. This paper presents such a sensor. Our sensor is built using two dielectric elements with different permeability coefficients. A finite element method simulation is used to estimate the parameters of a constructed sensor. Besides simulations, a laboratory model of a sensor was built and tested in a medium-voltage substation. Our results provide a proof of concept for the presented sensor. Some errors in voltage reconstruction have been traced to an oversimplified data acquisition and transmission system, which has to be improved during the further development of the sensor.

scholarly journals Applications, challenges, and needs for employing synthetic biology beyond the lab

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sierra M. Brooks ◽  
Hal S. Alper
Keyword(s):  
Synthetic Biology ◽  
Great Promise ◽  
Long Term Storage ◽  
Autonomous Function ◽  
Recent Advances ◽  
Resource Limited ◽  
Major Application ◽  
Further Development ◽  
Probiotic Delivery

AbstractSynthetic biology holds great promise for addressing global needs. However, most current developments are not immediately translatable to ‘outside-the-lab’ scenarios that differ from controlled laboratory settings. Challenges include enabling long-term storage stability as well as operating in resource-limited and off-the-grid scenarios using autonomous function. Here we analyze recent advances in developing synthetic biological platforms for outside-the-lab scenarios with a focus on three major application spaces: bioproduction, biosensing, and closed-loop therapeutic and probiotic delivery. Across the Perspective, we highlight recent advances, areas for further development, possibilities for future applications, and the needs for innovation at the interface of other disciplines.

scholarly journals Sustaining Trade during COVID-19 Pandemic: Establishing a Conceptual Model Including COVID-19 Impact

2021 ◽  
Vol 13 (10) ◽  
pp. 5418
Author(s):  
Nashwan M. A. Saif ◽  
Jianping Ruan ◽  
Bojan Obrenovic
Keyword(s):  
International Trade ◽  
Bilateral Trade ◽  
Production Costs ◽  
Research Directions ◽  
Economic Distance ◽  
Conceptual Paper ◽  
Sudden Decrease ◽  
Further Development ◽  
Conceptual Research

The conceptual research aims to identify antecedents conducive to bilateral trade during the COVID-19 pandemic. Considering the relevance of bilateral trade for foreign policy and economy studies, there is a need for a renewed framework in times of extreme economic instability. As international commerce is essential for improving the country’s economy, we have examined how economic distance, population, trade percentage of GDP, exchange rate, and political changes interconnect and relate to COVID-19, influencing trade flows. This conceptual paper illustrates the likely impact of COVID-19 on international trade by exploring pandemics’ effects on standard trading parameters such as GDP, distance, policy stability, and population. We model the resulting shock as a multifaceted variable reflected in capital underutilization, manufacturing output decline, international trade costs inflation, production costs inflation, decrease in demand for certain services and shift from everyday needs towards activities that exclude the proximity between people, e.g., proclivity towards virtual market products. The sudden decrease in GDP and bilateral trade, as well as FDI, is amplified by further development of pandemics’ long-term consequences. We take COVID-19 to be a technological, financial, and policy shock significantly influencing international trade and economic development and argue that it will have a varying impact on diverse sectors and economies. The paper offers preliminary insight into the pandemic-related economics that are unfolding and deduce recommendations on positive changes in trading policy to fully leverage on arising trading opportunities and point to potential research directions.

scholarly journals Giant Vesicles Produced with Phosphatidylcholines (PCs) and Phosphatidylethanolamines (PEs) by Water-in-Oil Inverted Emulsions

Life ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 223
Author(s):  
Boying Xu ◽  
Jinquan Ding ◽  
Jian Xu ◽  
Tetsuya Yomo
Keyword(s):  
Encapsulation Efficiency ◽  
Analytical Study ◽  
Giant Vesicles ◽  
Imaging Flow Cytometry ◽  
Artificial Cell ◽  
Transfer Method ◽  
Long Term Preservation ◽  
Natural Cell ◽  
Cell Construction

(1) Background: giant vesicles (GVs) are widely employed as models for studying physicochemical properties of bio-membranes and artificial cell construction due to their similarities to natural cell membranes. Considering the critical roles of GVs, various methods have been developed to prepare them. Notably, the water-in-oil (w/o) inverted emulsion-transfer method is reported to be the most promising, owning to the relatively higher productivity and better encapsulation efficiency of biomolecules. Previously, we successfully established an improved approach to acquire detailed information of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)-derived GVs with imaging flow cytometry (IFC); (2) Methods: we prepared GVs with different lipid compositions, including phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and PC/PE mixtures by w/o inverted emulsion methods. We comprehensively compared the yield, purity, size, and encapsulation efficiency of the resulting vesicles; (3) Results: the relatively higher productivities of GVs could be obtained from POPC, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dilauroyl-sn-glycero-3-phosphoethanolamine (DLPE), DOPC: DLPE (7:3), and POPC: DLPE (6:4) pools. Furthermore, we also demonstrate that these GVs are stable during long term preservation in 4 °C. (4) Conclusions: our results will be useful for the analytical study of GVs and GV-based applications.

scholarly journals Circular Agreements—Exploring the Role of Agreements and Deals as a Political Tool for a Circular Economy

2021 ◽  
Author(s):  
Nils Johansson
Keyword(s):  
Value Chain ◽  
Circular Economy ◽  
Policy Instruments ◽  
Alternative Form ◽  
Advantages And Disadvantages ◽  
Free Rider Problem ◽  
Political Governance ◽  
The Eu

AbstractA problem for a circular economy, embedded in its policies, tools, technologies and models, is that it is driven by the interests and needs of producers, rather than customers and users. This opinion paper focuses on an alternative form of governance—agreements, which thanks to their bargaining approach brings actors from across the value chain into the policy process. The purpose of this opinion paper is to uncover and analyse the potential of such agreements for a circular economy. Circular agreements aim at increasing the circulation of materials and are an emerging form of political governance within the EU. These agreements have different names, involve different actors and govern in different ways. However, circular agreements seem to work when other types of regulations fail to establish circulation. These agreements bring actors together and offer a platform for negotiating how advantages and disadvantages can be redistributed between actors in a way that is more suitable for a circular economy. However, circular agreements are dependent on other policy instruments to work and can generate a free-rider problem with uninvolved actors. The agreements may also become too detailed and long term, which leads to problem shifting and lock-ins, respectively.

scholarly journals COVID-19 Shutdown: A Qualitative Study on Pearls and Pitfalls

Proceedings ◽  
2021 ◽  
Vol 74 (1) ◽  
pp. 4
Author(s):  
Naciye Güliz Uğur
Keyword(s):  
Qualitative Study ◽  
Human Health ◽  
Social Distance ◽  
The Other ◽  
Adoption Of Technology ◽  
Family Ties ◽  
Advantages And Disadvantages ◽  
Modern Period ◽  
Long Term Impact

The extraordinary and tragic conditions that humanity has not experienced before in the modern period have become ordinary, namely, a “new normal” with the presence of the COVID-19 pandemic. COVID-19 has had frightening consequences for human health and has caused one million deaths as of September 2020. On the other hand, it has set a new standard of good habits, approaches, and benefits. Due to its global and long-term impact, this unique virus has laid the groundwork for unprecedented helping and sharing behaviors between people and countries. In this study, findings are compiled from the open-ended responses of 626 individuals, all of whom live in Turkey. Within the study’s scope, individuals were asked about the unique advantages and disadvantages of the restrictions imposed under COVID-19. While the categories of economy, social distance, and health came to the fore among the harms, the strengthening of family ties, adoption of technology, and the spread of solidarity culture were mentioned among the advantages.

scholarly journals Optimised calibration programmes for comparators for instrument transformers

2021 ◽  
Vol 88 (2) ◽  
pp. 122-131
Author(s):  
Christian Mester
Keyword(s):  
Experimental Study ◽  
Operating Principle ◽  
Device Under Test ◽  
Operating Range ◽  
Ratio Error ◽  
Phase Displacement ◽  
Instrument Transformers ◽  
Instrument Transformer ◽  
Method Of Measurement

Abstract Traditionally, instrument transformers are calibrated using bridges. By definition, bridges use the null method of measurement. The traditional calibration programme for instrument transformer bridges characterise namely this null measurement. Many new commercial comparators for instrument transformer use a very different method. They sample the secondary signals of reference and device under test (dut) transformer independently. Based on the samples, magnitude and phase of both signals are determined. Ratio error and phase displacement are calculated. Consequently, the significance of their calibration using the traditional calibration programme is limited. Moreover, the operating range of modern comparators is much larger than that of bridges. The additional versatility cannot be used without an adapted calibration programme. This article analyses the calibration programmes for both technologies. An experimental study confirms both the suitability of the new calibration programme and the need to chose the calibration programme depending on the technology of the device to be calibrated. The conclusion is very general and applies to all measurement problems where an operating principle is replaced by another – when changing the operating principle, it is important to check the calibration programme and adapt it if necessary.

scholarly journals The Impact of COVID-19 on Hospitality Industry in Greece and Its Treasured Santorini Island

2021 ◽  
Vol 13 (14) ◽  
pp. 7906
Author(s):  
Nikola Medová ◽  
Lucie Macková ◽  
Jaromir Harmacek
Keyword(s):  
Social Impact ◽  
Tourism Sector ◽  
Challenges And Opportunities ◽  
Multiple Variables ◽  
Hospitality Sector ◽  
Tourism And Hospitality ◽  
The Impact ◽  
Further Development

This paper focuses on the dynamic of the recent upheaval in the tourism and hospitality sector due to the COVID-19 epidemic in Greece and Santorini island. It uses the case study of a country one-fourth of whose GDP consists of tourism. We compare the available statistical data showing the change in variables in the previous years with 2020 and look into the new challenges and opportunities posed by the drop in the numbers of visitors and flights. We focus mainly on the economic and social impact on the destination and possible future scenarios for further development in the area. Data show a significant effect of the pandemic on multiple variables, such as the long-term trend of the importance of tourism sector in GDP in Greece, the number of flights and visitors to Greece and Santorini island, and the contribution of tourism and travel to GDP. Based on the available data, we also construct three foresight scenarios that describe the possible futures for Santorini island in terms of the pandemic evolution. These scenarios may help various stakeholders and policymakers to be better prepared for different developments that may appear.

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