Negative Heat Capacity: Inapplicable IEC Standard to High-voltage Cable with Large Cross-sections

Experiment of this paper, with respect to temperature rising, was carried out on two cables with a sectional area of 2500 mm2, and the thermal capacity parameters of the cable were inversely calculated using the collected temperature data of each layer of the cable, and the characteristic curve of thermal capacity changing with temperature was drawn. The characteristic curve indicates that the thermal capacity parameters of the cable tend to have negative values, which is due to the IEC standard is inapplicable to accurately calculation of the heat flow of the cable with a sectional area of more than 1600 mm2. Therefore, it can be inferred that the calorific value of cable core is less than the actual calorific value. The discovery of this phenomenon will greatly affect the dynamic load calculation and evaluation of large-capacity transmission cable lines. More research needs to be invested to solve this problem.