A strand or cable consists of a central core surrounded by a number of wires wound helically in a single layer or multilayers. There are three modes of contact in a simple straight strand. The first type is a core-wire contact in which the wires in the layer are in contact with the core only. In the second type, the wires in the layer are in contact among themselves and not with the core, while in the third type there is a coupled contact among the core and all the wires. Most literature handled the cable assembly with either the core-wire or the wire-wire contact because of the simplicity of the loads acting in these distinct contact modes. An attempt is made in this paper to model the strand with a coupled core-wire and wire-wire contact and deduce its equations of equilibrium. The numerical analyses of strand force, twisting moment, strand stiffness, contact force, and contact stress are carried out based on the equilibrium of thin rods and the results are compared with earlier research works. The importance of the inclusion of interface forces and their effects is studied.
Transformer oil-based nanofluids have become popular research topic due to their enhanced dielectric and thermal properties. Considering the sustainability aspects of extending the life of transformer oil, it is imperative to conduct research on the effect of transformer oil with nanofillers. In the present work, the influence of conducting magnetite (Fe3O4), semiconducting titania (TiO2) nanoparticles and combination of Fe3O4 and TiO2 nanoparticles (multi-nanoparticle) on AC breakdown voltage are investigated for various concentrations. Nanofluid prepared using multi-nanoparticle shows enhanced AC breakdown voltage (BDV) of transformer oil compared with unfilled oil. Enhancement in BDV of 22% is observed with combination of 0.0025 wt% Fe3O4 and 0.0075 wt% TiO2. In addition, the effect of titania nanoparticles dispersed into service-aged transformer oil with a weight percentage of 0.01% is investigated. Comparative study of breakdown strength and viscosity of nanofluid with unfilled oil is performed. Service-aged oil sample shows increased BDV of 15% with TiO2 nanoparticles. The degradation in service-aged transformer oil is analyzed using UV–vis and Fourier Transform Infrared (FTIR) spectroscopy. The characteristics of oil samples are analyzed using fluorescence spectroscopy.
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