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Vol. 18 (2015 year), No. 4

Antropov I. M., Efimov B. V., Nevretdinov Yu. M.
Influence of line isolation overlappings on formation of lightning overvoltages

The model of substation protection against lightning waves with considered multiple overlappings of line isolation has been presented. Influence of multiple overlapping of isolation on line support on formation of lightning overvoltages has been shown. Ambiguity of determination of lightning current dangerous parameters at the fixed length of its front has been revealed

(in Russian, стр.8, fig. 6, tables. 2, ref 7, Adobe PDF, Adobe PDF 0 Kb)

Vol. 19 (2016 year), No. 4, DOI: 10.21443/1560-9278-2016-4

Kuklin D. V. , Efimov B. V.
Influence of location of the lead wires on calculation results of grounding transient characteristics of a grounding rod

For calculations and measurements of transient characteristics of groundings, the current and potential lead wires are frequently used accordingly to inject the current into the grounding and find the grounding potential rise (GPR). The results of the calculations and measurements can be dependent on the location of the current and potential lead wires due to mutual influence between them and the grounding wire. It is important to determine to what extent the location of the wires influences the calculation results for the grounding with a simple configuration. Notably, in contrast to the measurements, for the calculations it is possible to locate wires vertically, also the potential lead wire can be replaced by the integral of the electric field. For the calculations the finite difference time domain method (FDTD) has been used in the work. In order to estimate to what extent the calculated GPR can be influenced by location of the wires, calculations with different wires locations have been carried out. An analysis of the calculation results has been made. There are calculation methods in which the injection of the current and calculation of the GPR are performed without the current and potential lead wires. The method based on the telegrapher's equations is one of such methods. In order to determine what location of the lead wires gives the same calculation results as those of the method that uses the telegrapher's equations, a comparison of calculation results of two methods has been made. Based on the calculation results it can be concluded that the calculated transient characteristics depend to a different extent on such factors as mutual location of the lead wires and the grounding wire, replacing the potential lead wire by the integral of the electric field, electrical parameters of the soil. Location of one of the lead wires above the grounding wire significantly reduces the calculated GPR. Calculation results for a perpendicular location of three wires (the lead ones and the grounding wire) using the FDTD method correspond to those of the method based on the telegrapher's equation

(in Russian, стр.8, fig. 8, tables. 0, ref 7, Adobe PDF, Adobe PDF 0 Kb)

Vol. 21 (2018 year), No. 4, DOI: 10.21443/1560-9278-2018-21-4

Selivanov V. N., Barannik M. B., Bilin V. A., Efimov B. V., Kolobov V. V., Sakharov Ya. A.
Analysis of long-term monitoring of autotransformer neutral currents

The Kola Science Center of the Russian Academy of Sciences together with the Polar Geophysical Institute is carrying out research concerning the effect of geomagnetic storms on the state of electrical networks and transformer substations on the Kola Peninsula and in Karelia. A regional system for monitoring currents in transformer neutral was created which collected a huge array of information on the influence of geomagnetic disturbances on a 800 km electric network. Overhead transmission lines are giant antennas that capture electromagnetic energy of any nature from the surrounding space. An analysis of the data accumulated over many years shows that in the current of a grounded neutral there are reliable responses to a wide range of electromagnetic phenomena on the Earth and in the near-Earth space: pulsed and quasisinusoidal pulsations of the geomagnetic field, extremely-low frequency components of artificial signals, lightning discharges and internal transients in the power system. To identify phenomena, a visual method is used to analyze the time and spectral characteristics of signals, which takes a long time and is rather subjective. There is always the possibility that some important, previously unidentified phenomena will go unnoticed. The paper describes the characteristic features of signals detected in neutral currents of power transformers. Algorithms of digital signal processing that can be used to create programs for automatic analysis of large data sets have been considered. To the greatest extent, numerical methods based on wavelet expansion and Fourier transform are suitable for studying nonsteady signals of a complex structure.

(in Russian, стр.8, fig. 6, tables. 0, ref 7, adobePDF, adobePDF 0 Kb)