Thermal characteristics of energized shielded drag and an unshielded reeled trailing cable

Research to determine the relationship between current load and temperature rises in shielded and reeled coal mine trailing cables is discussed. Temperatures within and on the cables were measured with thermocouples and the data recorded over time by computer. Steady-state DC load tests with two type SHD-GC cables revealed that only 3 to 7% more current than the Insulated Cable Engineers Association (ICEA) ratings for shielded cables was required to reach rated insulation temperature. The ability of the metallic shielding to absorb heat was reflected in longer thermal time constants than with unshielded designs. Steady-state temperature rises were monitored in a two condition unshielded, flat cable wound on a shuttle car cable reel. Stabilized axial temperature profiles exhibited maxima midway between the reel flanges. Static derating factors, expressed as percentages of open-air ampacity, were considerably less than ICEA ratings for reeled cables. The findings support a tentative contention that deratings for trailing cables wound on reels should be based on the specific cable configuration