In this paper, the properties of AE signals originating from phenomena occurring during magnetization of ferromagnetic materials which are used to construct power transformer cores are presented. The AE signals in a selected power oil transformer were recorded and analyzed. The analysis included, i.e., time, frequency, and time-frequency analyses, calculations of amplitude distributions of the signals and defined AE descriptors, determination of the descriptor map on the side walls of transformers, as well as a detailed analysis of selected part of the signals.

The maps of descriptors were analyzed in the frequency bands of 20–70 kHz, 70–100 kHz, and 100–200 kHz. The analysis of the properties of the signals was performed in time and frequency domains. Based on the analysis, there were identified the AE signals originating from the phenomena occurring during the core magnetization of a power oil transformer. To identify those phenomena, the maps of the ADC descriptor calculated in the band of 20–70 kHz when selecting the measurement points in which there were no AE sources from partial discharges were used.

An analysis of magnetoacoustic emission signals in the bands of 70–100 kHz and 100–200 kHz was also performed. The analysis of the signal properties in such an extended frequency range allowed determining the properties of the magnetoacoustic signals coming from core sheets of power oil transformers.

This paper aims to present a new equivalent scheme of multi-windings traction transformers, based on multiport purely inductive circuit. The mathematical background of this equivalent scheme is described. The determination of the different scheme elements is made through a finite-elements calculation of both main and leakage inductances, for the case of a four-winding transformer. A procedure is defined, which allows to estimate the values of these elements from some measurements on the transformer at no-load and short-circuit operations. A specific strategy of short-circuit tests is described, allowing to determine all parameters in a rather simple way.

Electronic voltage transformers (EVT) and electronic current transformers (ECT) are important instruments in a digital substation. For simple, rapid and convenient development, the paper proposed an on-site calibration system for electronic instrument transformers based on LabVIEW. In the system, analog signal sampling precision and dynamic range are guaranteed by the Agilent 3458A digital multimeter, and data synchronization is also achieved based on a self-developed PCI synchronization card. To improve the measurement accuracy, an error correction algorithm based on the Hanning window interpolation FFT has good suppression of frequency fluctuation and inter-harmonics interference. The human-computer interface and analysis algorithm are designed based on LabVIEW, and the adaptive communication technology is designed based on IEC61850 9-1/2. The calibration system can take into account pairs of digital output and analog output of the electronic voltage/current transformer calibration. The results of system tests show that the calibration system can meet the requirements of 0.2 class calibration accuracy, and the actual type test and on-site calibration also show that the system is easy to operate with convenience and satisfactory stability.

A high accurate electronic instrument transformer calibration system is introduced in this paper. The system uses the fourth-order convolution window algorithm for the error calculation method. Compared with Fast Fourier Transform, which is recommended by standard IEC-60044-8 (Electronic current transformers), it has higher accuracy. The relative measuring errors caused by asynchronous sampling could be reduced effectively without any special hardware technique adopted. The results show that the ratio error caused by asynchronous sampling can be reduced to 10-4, and the phase error can be reduced to 10-3 degrees when the deviation of frequency is within ±0.5 Hz. The present method of measurement processing is achieved by a high-accuracy USB multifunction data acquisition (DAQ) card and virtual measurement devices, with low cost, short exploitation period and high stability.

In this study a group of selected transformation kinetics equations is applied to describe the isothermal ferritic transformation in austempered ductile iron (ADI). A series of dilatometric tests has been carried out on ADI at different temperatures. The obtained experimental data are utilized to determine the parameter values of the considered kinetic equations. It is found that the transformation kinetics models by Starink, Austin and Rickett are substantially more effective at describing the ferritic transformation in ADI than the much celebrated Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Furthermore, it is demonstrated that evaluating the kinetic parameters using the least squares method instead of calculating them from vastly used formulas can significantly improve the accuracy of the JMAK model’s predictions.

“Isolation would be most unfortunate. We would be doing science in our own company, completely indifferent to what is happening outside our own universe. This would be totally self-destructive and I hope it will never happen,” says Professor Michał Głowiński in an interview with Grzegorz Wołowiec, titled “A Time Unexpected,” a fragment of which is presented below.

Dr. Artur Obłuski of the University of Warsaw tells us about research into political, social, and religious transformations in Sudan in the Middle Ages, the present-day importance of archaeological discoveries, and the meaning of the word “UMMA.”

On 16 July 2019, another significant amendment to the provisions of the Act on the transformation of the right of perpetual usufruct to land built-up for residential purposes into the ownership title to that land was introduced. The purpose of this research paper is to analyse the influence of the amendments to the regulations on the scope of the real properties subject to the transformation of perpetual usufruct into ownership, to identify the problems and to assess the status of the implementation of the transformation process in practice. The conducted research has resulted in the presentation of the structure of land on the example of a selected city, in particular with reference to real estate let into perpetual usufruct for residential purposes. The author has also determined the status of the implementation of the transformation process in practice as well as the problems hindering the issuance of certificates for all transformed properties within the statutory period. The progress of the transformation process in a given area depends, inter alia, on the scope of real properties subject to this transformation, the requirement to perform additional analyses, including those regarding non-compliance of the legal and factual state of the property, and the assessment of the existence of public aid and related payments. This study is a continuation of the earlier research, extended by the effects of the regulations introduced in July 2019, as well as by the assessment of the progress in the transformation process in practice.

In this article, the author will try to conditionally transform the energy capacities of NNEGC

Energoatom by converting a liability into an asset using the example of bitcoin. With a surplus of

nuclear power generation, one of the modern tools for using excess electricity is directing it to cryptocurrency

mining. The author of the article will try to calculate the possibilities of Ukrainian NPPs

in the cryptoindustry market by analyzing the competitiveness, market trends and the approximate

profitability of this kind of activity. The essence of the article lies in the intervention of the state

energy giant in completely new activities, partial monopolization of the market and interference

in the activities of decentralized cryptocurrencies, as well as the very novelty of combining two

different fields of activity and the global nature of the consequences. Mining can be used to convert

the underdeveloped electricity or all of Energoatom’s capacities totally, but at the same time it can

also affect the cryptoasset market in the field of decentralization, as the primary cost factor to affect

the price of assets and allow for obtaining super-profits at a state enterprise. The author of the article

tries to understand the profitability of such actions and, in general, to understand the globality

of the idea. The results of the entry of the national energy giant into the cryptoasset market will

change the global processes in the ecosystem of the cryptoindustry and change the situation both

on the electricity market in the region and, in general, will affect the processes of globalization and

unification of the financial sectors of the economy.

The article discusses the problem with modifications of plans of water areas and the forms of their borders which have been inscribed into the history of all city structures related to water. It can be observed that the modifications made in recent decades very often concern the transformations of former industrial sites. Many such structural changes are taking place within signifi cant areas which have fragmented central parts of cities and created voids in the urban fabric. They are being applied to many former shipyards and ports. Research shows that the formation of new connections between land and water in these transformation processes is essential. More frequently, those conversions that are currently being realized change the constructions of wharves and lead to the development of plans drawing new borders between land and water. In these cases water is introduced into land areas and new land surfaces are being created over existing bodies of water. These operations can be considered extremely valuable in achieving the intended eff ects of transformations of post-industrial areas. They are perceived as an excellent possibility to strengthen the relationship between the city structure and water. At the same time they create an opportunity to achieve a high quality of architectural and landscape solutions and the quality of spaces in both social and economic terms.

Gothenburg is the second-largest city in Sweden, capital of Västra Götaland County Region. It is situated on the west coast of Sweden with the port area located along the Göta Älv River. Due to economic restructuring, waterfront redevelopment emerges as an attractive option to boost economic growth of the city. The aim of this paper is to shed light on conditions of the transformation process of two neighboring areas: Frihamnen and Ringön. Publicly initiated and privately executed waterfront redevelopment in Gothenburg transforms industrial grounds into residential and service oriented areas in Eriksberg, Lindholmen and Frihamnen. The collaborative process of a “developer dialogue” crafts a redevelopment in a consistent way with taking into consideration city’s long-term planning strategy, specifi c needs and opportunities of the neighbourhoods, but also market and fi nancial realities of development community. Another example is a slow and spontaneous transformation of post-industrial areas in Ringön, where still active small industrial fi rms, services, cultural and artistic initiatives take place in the close proximity to the city centre. Results show the waterfront transformation attracts “developers’ dialogue” giving the opportunity to build a coherence for spatial, environmental and socio-economic development. Yet fragmented redevelopment of brownfi eld areas strengthen polarization between dynamic and carefully planned Frihamnen and spontaneously growing Ringön. This paper contributes to the knowledge on the complexity of urban post-industrial transformation.

The radiation of sound waves from partially lined duct is treated by using the mode-matching method in conjunction with the Wiener-Hopf technique. The solution is obtained by modification of the Wiener-Hopf technique and involves an infinite series of unknowns which are determined from an infinite system of linear algebraic equations. Numerical solution of this system is obtained for various values of the problem parameters, whereby the effects of these parameters on the sound diffraction are studied. A perfect agreement is observed when the results of radiated field are compared numerically with a similar work existing in the literature.

Extensive efforts have been made for many years by the power generating industry to replace conventional solid and liquid insulation with synthetic materials. Those measures are aimed at increasing the load capacity, improved fire safety and extending transformer life during exploitation. Modern insulating materials include aramid fibre-based paper and insulating fluids made of synthetic and natural esters. The paper presents research results of the electrostatic charging tendency (ECT) of mixtures of fresh and aged mineral oil Trafo En with synthetic ester Midel 7131 and natural ester Midel 1204. The measurements were taken in a flow-through system using the pipes made of metal, cellulose and aramid paper. The influence of the liquid flow velocity, the type of material of the measuring pipe and the mixture content on the level of the streaming electrification current generation was determined.