Many factors affect the loading of the underground power cables, such as ambient temperature, depth of laying of cable, number of parallel circuits of cable, and thermal resistivity of the surrounding soil. One important factor, usually ignored, is the formation of dry zones around the underground power cables. Dry zones are usually formed around underground power cables under loading conditions due to the migration of moisture within the soil. In this paper, the effect of the formation of the dry zone on the ampacity of underground power cables is investigated. The derating factor for the formation of dry zones around underground power cables is suggested and calculated for different types of natural backfill soil. IEC 60287-1-3 is taken as a reference. Experimental work was conducted to study the phenomena of the dry zone as related to different types of soils.

To improve the performance and increase the lifetime of oil‐filled transformers, the thermal and dielectric properties of the transformer oil should be enhanced. Recently, nanotechnology was used as an effective science in the field of transformer oil development. In this study, barium titanate (BT) nanoparticles were inserted into the base transformer oil by a concentration of 0.005 g/L as an individual nanofluid sample (INFS). This insertion enhances the heat transfer coefficient by 33% but the breakdown voltage (BDV) was decreased by >10%. To overcome this problem of dielectric properties degradation, other three hybrid nanofluid samples (HNFS) were prepared using three different types of metal oxide (MO) nanoparticles; titania, alumina, and silica. These samples were prepared by adding a concentration 0.01 g/L of MO nanoparticles together with 0.005 g/L of BT nanoparticles into the oil. The thermal and dielectric properties of HNFS were measured to study the behaviour of nanoparticles hybridisation on transformer oil properties. HNFS using titania nanoparticles provided the best composition regarding either BDV or heat transfer coefficient. Dynamic light scattering (DLS) technique was used to evaluate the particle size distribution of hybrid nanoparticles and to clarify the corresponding physical mechanisms behind the obtained enhancement.

The current study is to investigate the influence of inserting chemically modified titanium oxide (TiO ₂ ) nanoparticles on the dielectric and mechanical properties of the commercial compound Polyvinyl Chloride (PVC) used in insulating power cables. The surface modification of TiO ₂ nanoparticles was performed using vinyl silane coupling agent after activating their surfaces with methane-sulfonic acid. The PVC pellets were first dissolved using suitable solvent. Then, PVC/TiO ₂ nanocomposites, with different loadings of nanoparticles, were synthesized with the aid of ultra-sonication for better dispersion of nanoparticles. The morphology of the prepared nanocomposites was studied by field emission scanning electron microscopy (FE-SEM), and their mechanical properties were studied by performing tensile test at speed of 50 mm/min. The results showed that the insertion of functionalized nanoparticles is able to increase the tensile strength and the Young's modulus of the prepared samples, however it decreases their elongation. The dielectric properties, such as dielectric constant and dielectric loss, were also studied in a range of frequencies between 20 Hz and 1 MHz. Moreover, AC breakdown voltage of prepared samples was measured under uniform and semi-uniform field, and then, AC dielectric strength was evaluated using Finite Element Method (FEM) for semi-uniform field. For further evaluation, DC breakdown voltage was also measured under uniform field. PVC/TiO ₂ nanocomposites with functionalized TiO ₂ exhibited better dielectric properties compared to that with un-functionalized TiO ₂ or that of base PVC. This may be attributed to the low surface energy of the functionalized TiO ₂ nanoparticles that prevented the agglomeration of nanoparticles and restricted the mobility of polymeric chains.

The precise evaluation and mitigation of the electric field generated by overhead transmission lines has gained great interest due to its impact on health and environmental issues. This paper presents a more generalized technique to calculate the electric field generated by power transmission lines in three dimension coordinates. This technique has been evolved, formulated, and applied to an Egyptian 500-kV single-circuit transmission line to evaluate the effects of line topology and terrain topography on the computed electric field. The results are compared with those produced by a 2-D technique.

This study aims to develop large‐scale polyvinyl chloride (PVC) nanocomposites for industrial application with power cables. To achieve this goal, PVC/silicon dioxide and PVC/titanium dioxide nanocomposites were fabricated with two different loadings of nanoparticles: 0.3 and 0.6 wt.%, in the presence of a suitable coupling agent that was used to reduce the agglomeration of nanoparticles and enhance the compatibility with polymer matrix. The coupling agent used in this study was the amino silane, and the process followed in the nanocomposites preparation was the melt blending method. The dielectric properties of these synthesised nanocomposites were studied by measuring the AC dielectric breakdown strength under the uniform field, then compared with the simulation results. The relative permittivity ( ɛ _r ), loss tangent (tan δ ), and DC electrical conductivity ( σ ) were also measured under frequencies ranging from 20 Hz to 1 MHz. In addition, the internal discharge measurements are performed using the traditional needle‐plane configuration with the help of phase‐resolved partial discharge (PD) analyser. This technique is used to analyse the PDs activity with respect to the phase angle of the applied voltage. It was found that the dielectric breakdown strength and PD resistance of the prepared samples are increased higher than that of the neat PVC; however, the ɛ _r , tan δ , and σ at 50 Hz are decreased.