Transient heating of buried power cables

An account is given of past work in the field of thermal transients in buried cables. From the publications of Morello and Van Wormer, it follows that the earliest simplified theoretical formulas for the conductor transient, produced for application to small-diameter cables, can be correct only for times sufficiently large for the effect of the thermal capacity of the cable to be negligible. For such large times, the simple exponential integral formula is shown to give a cable-surface attainment factor that is closer to the solution of the proposed model of Whitehead and Hutchings than is the more complicated Whitehead-Hutchings formula itself, although the difference is generally negligible. A comparison is given between the cable-surface attainment factor based on a constant rate of heat flow from the cable to the soil, and the corresponding exponential-integral formula.