Search
Results:
Vol. 23 (2020 year), No. 4, DOI: 10.21443/1560-9278-2020-23-4
Gracheva E. I., Gorlov A. N., Alimova A. N.
Algorithms and models of power losses in circuit breakers installed in networks
Determination of the main characteristics of the topology and technical condition of equipment underoperating conditions is necessary for analyzing and assessing power and electricity losses in intrashoplow-voltage industrial power supply networks. A comparative analysis of the technical characteristicsof automatic circuit breakers VA57-31 (KEAZ), NSX100 TM-D (Schneider Electric), DPX3 160 (Legrand), Tmax XT1 TMD (ABB) has shown that the main technical parameters of the machines are close in their values. At that it has been found out that automatic switches of the BA57-31 series have the lowest value of power losses per pole (7.5 W), whereas the automatic switches of the Tmax XT1 TMD series have the highest value (10 W). Thus, under the operating conditions of the equipment, the lowest value of power and electricity losses is characteristic of low-voltage electrical networks with installed circuit breakers of the BA57-31 series, and the highest value of losses is noted in in-shop systems with installed circuit breakers Tmax XT1 TMD. Using catalog data, the dependences of active power losses in circuit breakers on rated currents have been established; the algorithms have been developed and the obtained dependences have been modeled using approximating functions. The standard deviation of the compiled approximating functions has been calculated. Analytical expressions of the dynamics of power losses per pole have been determined as a function of the rated current. The graphical dependences of the investigated parameters of low-voltage equipment have been presented. The developed models are recommended to be used to increase the reliability of the assessment and refinement of the amount of active power and electricity losses in low-voltage electrical networks of industrial power supply systems, agrotechnical complexes, and enterprises of the public utility sector.
(in Russian, стр.8, fig. 6, tables. 2, ref 14, AdobePDF, AdobePDF 0 Kb)
Vol. 24 (2021 year), No. 4, DOI: 10.21443/1560-9278-2021-24-4
Gracheva E. I., Gorlov A. N., Alimova A. N., Mukhanova P. P.
Resistance change of contact groups of low-voltage electrical apparatus: Determining the laws
The main Russian and foreign manufacturers of low-voltage electrical devices – circuit breakers, fuses, magnetic starters, knife switches and packet switches are presented. The data of experiments for determining the resistance values of contact groups of low-voltage switching equipment are considered. The design features of the devices that determine the value of the resistances of the power circuits of low-voltage equipment are investigated and a classification is proposed depending on the design elements of the devices. A methodological approach and an algorithm for experiments and detailed analysis of the contact groups of devices are given. Experimental schemes for the study of contact groups are proposed. The data of the conducted experiments on the study of contact groups and the resistance values as a function of the flowing currents are shown. During the experiments it is revealed that the value of the resistance of the contacts changes depending on the value, type and time of exposure to current within +/–5 %. The laws that characterize the ratio of the resistance values of the structural components of devices (contact systems, thermal relay, coil of the maximum relay) have been revealed and defined. Empirical expressions and graphical dependences of the resistances of contacts and contact systems are obtained as a function of the magnitude of the rated currents of low-voltage contact equipment. The minimum sample size of the number of devices during experimental research is determined, sufficient to calculate the mathematical expectation of the resistances of the contact connections of the devices with a given accuracy. As a result of experimental studies, it is revealed that the resistance value of contacts and contact joints can increase during operation by 2–2.5 times. The established dependences of the change in contact resistance can be used to predict the technical state of electrical installations of intrashop low-voltage networks, to clarify the amount of electricity losses in shop networks up to 1 kV, and can also be used as an additional regulation for maintenance and scheduled preventive maintenance.
(in Russian, стр.10, fig. 10, tables. 3, ref 15, AdobePDF, AdobePDF 0 Kb)
Vol. 25 (2022 year), No. 4, DOI: 10.21443/1560-9278-2022-25-4
Petrov T. I., Safin A. R., Gracheva E. I., Ivshin I. V., Tsvetkov A. N., Basenko V. R.
Simulation of operating the equipment of mobile charging installation for charging electric vehicles to confirm compliance with climatic and mechanical performance groups
The development of electric transport is inextricably linked with the modernization of the associated infrastructure, and one of the factors for the slow introduction of electric transport in Russia is the small number of charging stations. But most of the existing solutions in the field of charging stations have a drawback – the lack of mobile installations. The team of Kazan State Power Engineering University (KSPEU) and Production Association "Zarnitsa" is developing a mobile electric vehicle charge units (MSCEU). At the design stage, a problem has arisen with the fact that it would be difficult to conduct constant tests on a full-fledged prototype of the MSCEU due to the weight and size parameters of the equipment. At the same time, there is a need for preliminary confirmation of the compliance of the MSCEU with the climatic (UHL1) and mechanical performance (M3) groups. To accomplish this task, it was decided to simulate the work of the MSCEU in the COMSOL software. For solving this problem, it is necessary to simulate a module of four rechargeable batteries in order to confirm the manufacturer's parameters, and thus verify the resulting model. Based on these results, a complete MSCEU model consisting of 1,200 batteries can be implemented, which can be used to check compliance with the given conditions. For thermal calculations, it is necessary to check the pre-selected parameters of the air conditioning power, and to select the thickness of the thermal insulation. As a result a 3D model has been implemented in COMSOL, the parameters of all materials used have been determined, the connections of solutions have been built, physics of processes and the type of a solver have been selected. Based on the simulation, the insulation thickness has been chosen, the results of simulation of operating the air conditioning system to maintain the operating temperature of the batteries have been obtained, and the results have been demonstrated that confirm the mechanical reliability of the MSCEU.
(in Russian, стр.12, fig. 9, tables. 4, ref 25, AdobePDF, AdobePDF 0 Kb)
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. 26 (2023 year), No. 4, DOI: 10.21443/1560-9278-2023-26-4
Petrova R. M., Gracheva E. I., Valtchev S., Miftakhova N. K.
Methods for assessing the reliability of in-shop power supply
Research activities in the field of development of electrical power and electrical equipment include the development of new approaches to assessing the reliability indicators of electrical equipment elements and in-house power supply systems in general. The study has examined methods for assessing the reliability of electrical equipment in intra-shop power supply systems using the example of a workshop network section, including its main elements: power transformer, low-voltage cable lines, distribution points, circuit breakers, magnetic starters, contactors, switches. The reliability parameters of the circuit are calculated relative to the distribution cabinet of the power (DCp) and the distribution point of the power (DPp); regarding each connection of DCp and DPp. The methods under consideration are recommended to be used to clarify the frequency and timing of maintenance and repairs of electrical equipment of the in-shop power supply system, as well as to analyze the reliability of operation and identify the least reliable sections of network diagrams. The presented calculation using the logical-probabilistic method by constructing a fault tree is advisable to use to estimate the frequency of power loss of DCp and DPp, as well as individual connections. For the studied circuits, graphical dependences of the probability of failure-free operation of electrical equipment and the occurrence of a failure over time have been constructed.
(in Russian, стр.15, fig. 10, tables. 4, ref 17, AdobePDF, AdobePDF 0 Kb)