Theoretical Study on Real-Time Rating of Short-Time Thermal Capacity of Duct-Installed Power Cables

Abstract

Recently utilities promote various researches to use existing equipments more effectively. Until now JCS (Japan Cable Maker's Association Standard ) method has been used to calculate the thermal capacity of power cables. However, in order to use existing power cables more effectively, detail calculations considering time varying thermal resistance and capacitance of surrounding soil are necessary. Regarding duct-installed power cables, duct temperatures can be measured by optical fiber distribution sensors which have been developed recently.
In this paper we propose a method to calculate the short-time thermal capacity of duct-installed power cables. The proposed algorithm is based on the estimation of the thermal resistance and capacitance of surrounding soil using continuously measured duct temperatures. In this algorithm an observer is used for the estimation of conductor temperatures, and also Genetic Algorithm is employed to estimate the thermal resistance and capacitance of surrounding soil accurately. The effectiveness of the proposed algorithm is demonstrated using the experiment data. It is shown that the application of proposed method improves the short-time thermal capacity of duct-installed power cables considerably.