Electricity

Congratulations of Academician V.Yu. Khomich on the 145th Anniversary of the Journal «Elektrichestvo»

editorial article — Sat, 05 Jul 2025 00:00:00 +0000

The Elektrichestvo Journal Turns 145

Pavel A. BUTYRIN — Thu, 29 May 2025 00:00:00 +0000

The year the Elektrichestvo (Electrical Technology) journal was established (1880) is also the year of both the beginning of worldwide electrification and the beginning of the work of the Electrotechnical Department of the Imperial Russian Technical Society, the core of Russia’s electrotechnical society. The article shows the role the Electrichestvo journal played in the co-evolution of electrical engineering as the genetic basis of modern industrial civilization and Russian society. The journal is considered as a chronicle of electrical engineering. The features of the articles published in the journal during the periods of worldwide electrification (1880-1930), the planned development of the country (from the late 1920s to the late 1980s), and modern time (since 1990) are analyzed. Information about the founders, editors, scientific and public recognition of the journal is provided. Attention is focused on the well–known authors of the journal: members of the Soviet Union’s Academy of Sciences (presently RAS), including its presidents, major electrical scientists and heads of the electrotechnical and electric power industries of the country. Attention is drawn to the topics and authors of the articles published in the journal for the past five years, to the geographical diversity of authors, who represent more than fifty cities annually, including those from abroad of Russia (Australia, Asia, America, Africa, Europe, which amount up to 20% of publications). The Elektrichestvo journal is presented as a scientific and cultural heritage of Russia.

Experience Gained from Implementing Low-Impedance Resistive Neutral Grounding in a 6 kV Megalopolis Grid

Thu, 29 May 2025 00:00:00 +0000

The experience gained from implementing low-impedance resistive neutral grounding in the 6 kV grid of a megalopolis is considered. The results obtained from experimentally verifying the performance of resistive neutral grounding by carrying out a single-phase earth fault test on a 6 kV substation bus section are given. It is shown that the existing guidelines for resistive neutral grounding in general meet the modern requirements and need only minor modification. It is confirmed that the resistive neutral grounding device made with the metal active part provides the final current value sufficient for the relay protection to come in action It has been proven experimentally that the time taken to clear a single-phase earth fault even by the backup protection is so short that any significant heating of the resistor metal active part is impossible. The article analyzes the emergency waveforms recorded during the actual clearing of ground fault current at the 110 kV Biryulevo substation operated by Rosseti Moscow Region PJSC. It is noted that all technical solutions adopted by the electric grid company specialists are correct.

Development of a Current-Limiting Reactor Electromagnetic System with an HTS Shield

Vasiliy V. ZUBKO, Victor E. SYTNIKOV, Nikolay A. SYROVATSKIY, Victor N. KARPOV — Thu, 29 May 2025 00:00:00 +0000

Fault current limiters (FCL) – chokes – are used in power systems for limiting short-circuit (SC) currents to prevent damage to electrical equipment and emergency situations from occurring. However, during normal network operation, a voltage drop occurs across the choke (mainly of an inductive nature), which is an undesirable effect. Given that maintaining voltage levels within acceptable ranges is one of the main requirements for ensuring reliable operation and survivability of electric power systems, limitations are imposed on the FCL impedance value. It is usually required that in the nominal network operation mode, the voltage drop across the choke does not exceed 5 % of the phase voltage. Such a limitation makes the choke protective action less efficient. Ideally, the choke should have relatively low reactance in the nominal mode and increased reactance in the SC mode. The aim of the study is to propose ways to modernize conventional chokes by using a shield consisting of short-circuited rings made of high-temperature superconducting (HTS) materials. As a result, choke reactance in the nominal operating mode is decreased significantly, and so is the voltage drop across it, while the SC current limitation efficiency remains the same. The newly developed choke with an HTS shield consists of two concentric inductively coupled windings. The primary winding, which is a choke conventional winding, remains unchanged, whereas the secondary winding is an HTS shield cooled to cryogenic temperatures (77 K). The article presents numerical models using which the choke inductance can be determined in the nominal mode (shielding mode) and in the short-circuit mode. The developed design of the HTS shield consisting of 71 rings is presented. The results of testing the choke with an HTS shield are given.

Vulnerability of Concentrated Above-Ground Structures to Lightning Strokes

Marat Z. GILYAZOV, Aleksey R. KORYAVIN, Evgeniy A. MILKIN — Thu, 29 May 2025 00:00:00 +0000

An analysis of existing methods for evaluating the vulnerability of concentrated above-ground structures to lightning strokes is given. It is pointed out that the vulnerability evaluation methods based on the protection angle and rolling sphere techniques recommended in IEC 62305 regulatory documents are rather formalized and devoid of physical essence. It is also shown that attempts to apply these methods yield results that contradict the data of field observations and cannot serve as a reliable basis for addressing practical lightning protection matters. In addition, the air-termination rod height is limited in these documents to 60 m, which does not make it possible to evaluate the vulnerability of ultra-high structures. An alternative approach implies the use of a probabilistic calculation method based on the physics of discharge in atmospheric air, the statistical nature of the process through which lightning orients on the system of structures, and the choice of an element within the system. This method has found its practical application in the relevant Russian regulations. To quantify the results of laboratory studies, an analysis scheme for the moment at which the downward leader head orients to a grounded concentrated object is considered. It is shown that when testing with impulse voltages with a front duration of several ms, the test results can serve as a good basis for transferring them to natural lightning. A simplified method is proposed for assessing the incidence of downward and upward lightning discharges on concentrated above-ground structures, the results of calculation by which are in good agreement with field observations.

Apparent Charge Estimation Based on a Measured Partial Discharge Signal

Thu, 29 May 2025 00:00:00 +0000

Measurement of partial discharge (PD) intensity proceeding from apparent charge values is a crucial stage in evaluating the internal insulation condition of high-voltage equipment. International and domestic standards define test methods for PD intensity measurements in new equipment under factory conditions; however, application of these methods under field conditions is often impractical for a number of reasons. For in-service monitoring of operating equipment, high-frequency measuring devices, such as high-frequency current transformers (HFCT), are commonly used. These devices make it possible to detect PD, determine their nature proceeding from characteristic features, and locate their occurrence spot in the equipment examined. However, the existing theory for estimating apparent charge based on PD signal integration and calibration fails to provide reliable results. The article presents a critical analysis of current PD measurement techniques and schemes. It explores the theoretical potential of and procedure for using direct and inverse Fourier transforms to eliminate methodological errors introduced by HFCT in PD measurements, for computing a refined image of the measured PD current and evaluating the apparent charge of recorded PD.

Electric Motor Condition Monitoring Based on a Convolutional Neural Network

Thu, 29 May 2025 00:00:00 +0000

Induction motors are among the most critical electrical equipment used in industrial processes, whose failure leads to significant economic losses. The article examines failures of the motor’s short-circuited rotor bars and discusses existing diagnostic methods based on stator current signals, and their limitations. The main challenge is the lack of data from a faulty motor under all possible operating conditions for training a neural network model. The article proposes informative features for detecting broken rotor bars and studies their behavior during non-stationary motor operation. Based on this, a data augmentation method is developed, which makes it possible to generate artificial current signals simulating motor operation under non-stationary conditions. This is achieved by introducing necessary distortions into the spectrum of preprocessed current signals, followed by applying the inverse Fourier transform. Proceeding from real and synthetic current signals, input images for a convolutional neural network (CNN) are constructed. Three time-series imaging techniques are used: Recurrence Plots, Markov Transition Fields, and Gramian Angular Fields. Based on experimental results, the three time-series imaging methods are compared, and the augmentation approach effectiveness is evaluated. The model trained on Recurrence Plots demonstrates the best accuracy improvement due to augmentation.

The Interaction Force between the Halves of a Uniformly Polarized Ellipsoidal Dielectric

Oleg P. POLYAKOV, Petr A. POLYAKOV — Thu, 29 May 2025 00:00:00 +0000

The article deals with a theoretical study of the ponderomotive coupling force between the components of uniformly polarized ellipsoid-shaped dielectric bodies. A new analytical solution to the problem of the interaction between two halves of a uniformly polarized dielectric ellipsoid of revolution has been found. In the special case of a uniformly polarized ball, the obtained solution coincides with the well-known Landau solution for the attraction force between the halves of a polarized ball. The dependence of the interaction force between the halves of a polarized ellipsoid on the ratio of its semi-axes is constructed. It is shown, within the framework of the Maxwell tension tensor method, that the main contribution to the coupling force is introduced by the tension of electric field lines in the virtual gap between the ellipsoid halves. When taking into account only the tension of the electric field lines, the deviation from the interaction force exact value is no more than 20%. The dependence of the attraction force between the halves of a polarized ellipsoid of a fixed volume on the ratio of its semi-axes is found. It has been established that this force has a maximum value for the case of a spherical ellipsoid. It is shown that when the ratio of the semi-axes tends to an infinitely large value (an elongated ellipsoid), the interaction force between its halves tends to zero. The same interaction force value is also achieved in the case of an infinitesimal ratio of the semi-axes, i.e., for an ellipsoid having an oblate shape.

Operating Modes of a Two-Unit Fast Charging Station for Electric Vehicles

Min Pu, Nikolay Volskiy — Thu, 29 May 2025 00:00:00 +0000

For the development of electric vehicles, both in Russia and abroad, it is necessary to create an extensive network of efficient electric charging stations. One of the factors restraining the spread of electric charging stations is the limitations on the consumption current and area of the installation, which are determined by the existing infrastructure. An electric charging station containing two power units was studied. Taking into account the identified limitations and current capabilities, operating modes of an electric fast charging station were proposed that provide simultaneous charging of two electric vehicles with minimal downtime. These modes were tested by computer modeling using the MATLAB/Simulink software package and experimentally tested at the EDISON60 fast charging station. Compared to existing modes, the proposed solution allows to reduce the time of simultaneous charging of two electric vehicles by up to 23% with a given limitation of consumption current from the three-phase infrastructure network, taking into account the possible maximum output current of the power modules. The presented material is intended for developers of electric charging stations with increased throughput.

Viktor Boleslavovich Demidovich (to the 75th Anniversary of the Birth)

editorial article — Sat, 05 Jul 2025 00:00:00 +0000

Eduard Petrovich Volkov (Obituary)

editorial article — Sat, 05 Jul 2025 00:00:00 +0000