Calculation of the equivalent thermal parameters of external environment for cable based on the real-time measurement data

Modelling the heat-transfer process of environment for laying electric cable makes for predicting the conductor's temperature in electric cable and calculating the potential current-carrying capacity. This passage put the heat-transfer process of environment for laying electric cable as first-order thermal resistance-thermal capacity model, and deduced the computational method of the thermal resistance and thermal capacity of the environment. The method's dependability was validated through an experiment of 110kV, 500-milimeter-square single conductor cable. Based on the data of the temperature rise experiment, it can be concluded that the computing results of the thermal resistance and thermal capacity of the environment are closed linked with the time interval and the volatility of the computing result was lower while the time interval was longer. The computational results of the external thermal resistance and thermal capacity stayed within the scope of thermal physical parameters of common soil material. Accordingly, the established model of the first-order thermal circuit was proved to be accurate. And the calculations of the environmental thermal resistance and thermal capacity were proved to be reliable
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