Existing underground cable ratings underestimate full capability of power consumption during summer. This leads to the demand of improved and more accurate ratings . An objective of this project is to look at the heat and moisture migration initiated by the heating of the medium surrounding the buried cables, which when subjected to prolonged heating under extreme condition leads to 'thermal runaway'. Identification of conditions under which 'thermal runaway' occurs will allow the improvement of the external parameters (such as soil thermal resistivity and capacitance) used in the existing cable ratings under the ground. A Philip-deVries model is used to look at the effects of drying-out.This involves looking at the changes of moisture content of the surrounding medium, the effects of native soil having different properties to that of backfill, backfills of different properties and environmental factors. A controlled environment model will be developed to monitor the changes in heat and moisture at the viccinity of the heated source.