Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Electrical Power and Machine

The maximum current carrying capacity of the power cables which buried in the ground is affected by many factors such as moisture content, soil thermal resistivity of surrounding soil, ambient temperature, depth of laying of cable and the formation of dry zone around the power and distribution cables, which lead to increase of the thermal resistivity and decrease in the maximum current carrying capacity. Under loading condition, heat generated from the cables raises the temperature of the surrounding soils and leads to thermal instability then formation of the dry zone. The dry zone formation affects the cables current carrying capacity and the cables insulation such as decrease in the cable life-time. In this thesis 12 types of soils are tested (sand, lime, 3 mixtures of sand and lime, clay, 3 mixtures of sand and clay, mixtures of sand & lime & clay, pure peat-moss and vermiculite materials). It is noticed that some types of soils formed the dry zone faster than others. The aim of this thesis is to determine the best type of the soil that can be used as backfill-material to reduce the dry zone effect on the cables. Also calculate the de-rating factor for the formation of dry zone for different types of soils. The velocity of dry band formation around different types of distribution cables and its radius are calculated by the aid of experimental results that obtained from the tests carried out on different soil types which are mentioned before

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