Thermal transients on buried cables

Power Cable Rating Calculations - A Historical Perspective [History]

“…previous work [21] on the treatment of the problems of three-conductor cables for the computation of shorttime overload ratings of solid-type and oil-filled cables installed in ducts. Two years later, Buller conducted a critical assessment of the previously published analytical formulas and techniques for the calculation of transient temperature rises in buried cables [25], [29]. He discussed the assumptions and performances of semiempirical formulas based on simple or series exponential expressions and Bessel functions and developed new improved equations for the temperature predictions in buried cables.…”

Transient heating of buried power cables

“…Shanklin and Buller 29 have given tables permitting the ready calculation of the conductor transient following the application of load cycles of rectangular, sinusoidal or peaked types (the peaked cycle refers to a partial load carried continuously, with a superimposed 1 h peak), but with a minimum loss factor of 0-3. The formula used by Shanklin and Buller for the conductor-temperature response, following the application of a unit-step-function applied load, is the modified exponential-integral formula obtained previously by Buller,9 to which is added some exponential terms to take account of the conductor-temperature rise above the cableor pipe-surface temperature. However, it does not appear obvious from the paper why the tables of conductorattainment factors are independent of some of the parameters involved in the expression for the response to a unit stepfunction applied load.…”

“…ratio of transient cable-surface-temperature rise to steady-state cable-surface-temperature rise The difference between the results obtained using the various techniques is dependent only on the different expressions used for <x(/), the cable-surface attainment factor. For this purpose the exponential-integral formula has been used by Buller, 9 Morello 19 and Neher, 20 while a separate expression has been used by Whitehead and Hutchings. 11 For certain standard British cables 24 the percentage difference involved has been shown 12 to be small, even for the most unfavourable cases.…”