An accuracy assessment method of calculating cable conductor temperature through surface temperature and actual loading current

Abstract

The control of cable transmission capacity is decided by the cable capacity, which is determined by the long-term enduring temperature. The cable capacity is usually calculated by the formula of IEC-60287, in which the conductor temperature is supposed to be 90°C (when its insulation is XLPE), and the cable surface reaches its maximal temperature. However, the maximum temperature of the cable surface is related to the load current. Therefore, taking into account the actual situation, the IEC formula is not so rigorous. In this paper, based on the thermal circuit method, the integrity calculation program is compiled by the MATLAB software, in which the conductor temperature is calculated according to the sheath temperature and the operating current. In order to validate the calculated result, an experiment is made. Then, the experiment data is compared with the theoretical calculated result. The error is analyzed when taking account the conductor loss related to the change of conductor temperature. Then, the relationship between conductor temperature and sheath temperature is given. It is shown that taking into account the conductor loss related to the change of conductor temperature, the thermal circuit method calculating conductor temperature based on the surface temperature and real-time running current can be applied. to It is not necessary to consider the effect of the external environment when the thermal circuit method is applied to engineering calculations.