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Vol. 26 (2023 year), No. 4, DOI: 10.21443/1560-9278-2023-26-4

Petrov A. R., Gracheva E. I., Valtchev S.
Study of technical parameters of magnetic starters and switches installed in workshop networks

The study of technical parameters of low-voltage switching devices of Russian production – magnetic starters PML and switches RE19 has been carried out. The problem of evaluating energy efficiency of operation of magnetic starters and switches installed in in-plant power supply systems has been presented. The main destabilizing factors significantly affecting the technical characteristics of switching devices with voltage up to 1 kV have been given. Reliability of functioning of the investigated devices, first of all, depends on the degree of wear of switching contacts. The dependences of the heating temperature of the contact areas of switching devices on the loading coefficient have been studied. It has been revealed that with the increase of loading of devices in the range from 1,0 to 2,0Inom the temperature of contacts and contact areas is within the permissible limits in accordance with the requirements of GOST 403-73. The main factors influencing the resistance of contact connections – current flowing through the contacts, their dimensions and heating temperature – have been shown. According to the results of theoretical and experimental studies approximating functions of dependences of resistance of contacts and contact connections of switching devices on rated current have been developed and errors of the calculated method of contact resistance estimation have been determined. The developed dependencies can be used to determine the equivalent resistance of networks of in-plant power supply when estimating the level of power losses, which will increase the reliability of the results obtained.

(in Russian, стр.11, fig. 5, tables. 4, ref 25, AdobePDF, AdobePDF 0 Kb)

Vol. 27 (2024 year), No. 4, DOI: 10.21443/1560-9278-2024-27-4

Petrov A. R., Gracheva E. I., Miftakhova N. K.
Improvement of the methodology for assessing power losses in in-plant power grids

To improve the reliability of calculations of electric power losses in low-voltage electric networks, it is necessary to take into account the influence of the main parameters of electrical equipment. In the course of the study, a structural diagram and an algorithm for determining the equivalent resistance of the section of the shop network have been proposed; the main factors determining the equivalent resistance of the circuit (resistance of low-voltage switching devices, heating temperature of conductors, ambient temperature, equipment load factor) have been identified; graphical dependencies of the change in the equivalent resistance of the radial and trunk sections of the circuit on the mean square equipment load factor and the heating temperature of conductors have been shown. The total error in estimating the equivalent resistance when calculating without taking into account the main studied parameters of equipment for radial, trunk and mixed circuits is 40 % or more. The error in the results of calculations without taking into account the resistance of contact connections of switching devices can reach 80 %. The obtained dependencies of the equivalent resistance on the main parameters of the equipment are recommended for use to improve the reliability of estimating electric power losses in intra-plant electric networks.

(in Russian, стр.10, fig. 4, tables. 4, ref 17, AdobePDF, AdobePDF 0 Kb)

Vol. 28 (2025 year), No. 4, DOI: 10.21443/1560-9278-2025-28-4/1

Verstunin A. Yu., Gracheva E. I., Petrov A. R., Abdullin L. I.
Application of the developed computer model to study the technical characteristics of low-voltage switching devices using the example of circuit breakers

The paper examines the issues of assessing the technical characteristics of circuit breakers (CB) installed in electrical networks of industrial enterprises. The aim of the work is to model the main technical parameters of the CB contact system: heating temperature, contact resistance and active power losses per pole of the device. The computer model has been developed in the COMSOL Multiphysics software package, the geometry of the contact system of the device has been made in the Solid Edge program. The obtained modeling results are compared with the calculated and experimental data, as well as with the data regulated by GOST 60947-2-2021, GOST 60898-1-2020 and GOST 403-73. Modeling errors are determined. The contact heating temperature and active power losses per pole, determined using the developed model as factors of operational efficiency, make it possible to increase the accuracy of assessing the technical condition of the devices. At the same time, the values of the heating temperature of the contact connections coincide with the data after 28-day tests of the CB according to GOST 60898-1-2020. Therefore we believe that the obtained data correspond to the experimental values of the heating temperature of the contact connections of the device. Power losses per pole of the studied devices do not exceed the values established by GOST 60898-1-2020. It has been found that the values of the resistance of the CB contact connections determined using the computer model are comparable to the experimental data. The use of the computer model will reduce the time for revision when designing the CB structure, as well as determine the optimal geometric parameters, contact pressure and roughness of the contact system. In the future this will allow us to predict the state of the CB contact system.

(in Russian, стр.14, fig. 11, tables. 4, ref 16, AdobePDF, AdobePDF 0 Kb)