Ghada M. Amer

Effect of the Formation of the Dry Zone Around Underground Power Cables on Their Ratings

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.

Performance of crops growth under low frequency electric and magnetic fields

The biological effects of extremely low frequency magnetic fields (ELF MFs) on living organisms have been explored in many studies, but few of them investigate the combination effect of both magnetic and electric fields act upon their growth. In this study, the biological effects of electric and magnetic field on the early growth of plants are presented using different beans. The electric and magnetic fields are produced using a specially-made test cell. The results indicate that the electric field has an enhancing effect on the early growth of the tested crops, however some morbid state phenomena were observed on some crops. Also, the effect and morbidity rate increases with electric field intensity.

Effect of high frequency electromagnetic fields on homogenous and inhomogeneous human head models

This paper describes the research work done by using the method of moment in investigating the effects of high frequency electromagnetic field (EM) on a homogeneous and inhomogeneous human head at various frequencies. The behavior of the human head under EM radiation is modeled as a homogenous model and a multilayer model in order to assess biological effects on the human head. The specific absorption rate (SAR) in the human head model is calculated, where the SAR is the main parameter used for indicating the effects of EM field.

Factors affecting transient response of grounding grid systems

Grounding system behavior under transient condition is investigated. Transmission line approach has been chosen to simulate the buried grounding system under lightning condition. Different models of buried grounding grids have been studied under lightning conditions. Sensitivity analysis of soil parameters and grounding grid dimensions have been studied to understand the effect of each parameter on the performance of grounding systems subjected to lightning.

The effect of the artificial backfill materials on the ampacity of the underground cables

The backfill materials around under-ground power cables affect the maximum current carrying capacity of these cables. Usually backfill soils around under-ground power cables lose their moisture content, forming dry bands around the cables and leading to an increase in the thermal resistance and decreasing in maximum current carrying capacity. But according to the results of the experimental works which are carried out in this paper, it is noticed that some types of soil lost their moisture content faster than the other. This means that the dry band around the cable in some soils form faster than the others. The aim of this paper is to determine the best type of artificial soil that can be used as backfill material to minimize the effect of dry bands that cause thermal failure to the cable insulation.