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.