Prevention of emergencies by monitoring the insulation condition of multi-core cables

Serhii Rudakov

National University of Civil Defenсe of Ukraine

http://orcid.org/0000-0001-8263-0476

Oksana Myrgorod

National University of Civil Defenсe of Ukraine

http://orcid.org/0000-0002-5989-3435

Ihor Hrytysyna

National University of Civil Defenсe of Ukraine

http://orcid.org/0000-0002-2581-1614

DOI: https://doi.org/10.52363/2524-0226-2021-33-20

Keywords: cable insulation, dielectric loss tangent, partial capacitance

Abstract

A method for measuring the partial capacities and the tangent of the dielectric loss angle of individual components of cable products that are in operation at energy facilities has been developed. This method is based on direct measurements of insulation components separately with subsequent assessment of the whole structure. This method makes it possible to assess in more detail the state of cable insulation, as cores, shields, metal sheaths are used as electrodes – to localize the probing electromagnetic field in certain parts of the cable: mainly in phase and solder insulation of power cables, in core insulation or in phase space control cables. Then, comparing the characteristics of the isolated areas of insulation with each other and with the basic products that have passed the accelerated resource tests, up to reaching the limit state – we make a reasonable conclusion about the current state of the cable product. However, in such measurements, the errors of partial capacitance measurements, and especially the tangent of the dielectric loss angle, can be large. The reason for this is the capacitive currents of the parasitic circuits discharged to the screen of the device. The paper proposes a method of reducing the mea-surement error, which limits the scope of the direct circuit only in cases where the capacity of the measured interval is much higher than the capacity of the parasitic circuits. The study on direct current is performed by devices with three terminals: two - measuring, the third - shielding - to remove excess current from the measuring circuit. The paper proposes such a scheme in the form of a triangle of capacitors, which allows for reliable measurements of the values of partial tanks, which compensates for the currents of the shunt circuits relative to the currents of the selected interval. The results of such control will allow to identify the areas of parameters that are most sensitive to the aging processes of cables, which, in turn, will prevent emergencies that could occur at energy facilities.

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