Abstract
A model of the piece-homogeneous interphase space of stranded cables is proposed, taking into account the influence of cracks oriented along the lines of force of the electric field. The cracks are filled with low molecular weight substances. The case of a probing electric field with a significant tangential component is considered.. The equivalent values of the tangent of the dielectric loss angle at various parameters of low molecular weight substances in the cracks of the polyethylene insulation of the conductor with a cross section of 2.5 mm2 were determined. The equivalent tangent of the angle of dielectric loss increases by (3-20) times when the dissipation of electrical energy by low molecular weight substances changes from 10% to 100% in a crack, which is 1% of the thickness of an intact section of polyethylene insulation. The distribution of the electric field for the general case of accumulation of low-molecular products in capillaries formed by slit-like gaps between isolated veins is obtained. A strong electric field in the smaller part of the gap between the insulated cores, which occurs at a core potential of 1 kV, contributes to the capillary absorption of decomposition products of both solid polyethylene insulation and water vapor from the atmosphere in the case of unshielded structures of multi-core cables. The asymmetric configuration of the probing electric field with a significant tangential component makes it possible to detect low-molecular decomposition products of solid polymer insulation, which are a sign of its aging. Differences experimentally observed in the value of tgδ with different schemes of examination of multi-core cables are related, to a greater extent, to the uneven distribution of substances dissipating electrical energy across the cross-section of the cable, and not to a change in the structure of the probing electric field. References 11, figure 5.
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