Analysis Frequency Response of Dielectric Losses for Diagnostics of Aging Medium Voltage Power Cable with Cross-Link Polyethylene

Medium-voltage power cables with crosslinked polyethylene insulation of power purpose are being intensively introduced into electric regional, city and regional networks. The development, implementation and operation of such cables are faced with the problem of ensuring minimum water content in cross-linked polyethylene insulation. To detect aging under the influence of moisture of cross-linked polyethylene insulation of high-voltage power cables in laboratory conditions, it is necessary to use high-frequency dielectric relaxation spectroscopy, which makes it possible to detect free moisture in cables and does not require studies under high voltage. The results of physical modelling confirmed the effectiveness of the use of high-frequency dielectric spectroscopy techniques to detect free moisture in the polymer insulation of new cables and operated in a humid environment. The relaxation maximum near the frequency of 10 MHz indicates the presence of free moisture in the polyethylene insulation of newly manufactured power cables. It is established that in the moistened polyethylene insulation on the frequency dependencies of the dielectric loss tangent there are additional peaks in the frequency spectrum of 500 kHz – 5 MHz.