Forced Cooling of Underground Electric Power Transmission Lines. Part II. Heat Conduction in the Cable Insulation of Force-Cooled Underground Electrical Power Transmission Systems.

摘要

Forced-cooled systems for oil-filled pipe-type cable circuits have recently been considered. In such systems the conduction resistance through the paper insulation of the cables is the limiting thermal resistance. Assuming bilateral symmetry,steady-state conditions,and two-dimensional heat transfer, a FORTRAN IV computer program was written to solve the heat conduction problem in the cable insulation for arbitrary configurations of a three-cable system. For a steel pipe, a cable system is most susceptible to overheating in the equilateral configuration with the three cables touching. Proximity effects are very significant in forced cooling,especially when cables are not provided with a copper tape under the insulation moisture seal assembly,accounting for as much as 21% of the total oil temperature rise between refrigeration stations. This figure,however,is reduced to 8% when 0.005inch thick copper tape is present.