Analysis on Transient Error of Simplified Thermal Circuit Model for Calculating Conductor Temperature by Cable Surface Temperature

The temperature of power cable conductor of being operated cable is the foundation to judge whether the cable reaches its rated current carrying capacity or not.To analyze the accuracy of cable conductor temperature calculated by simplified thermal circuit model,based on the thermal circuit model to calculate the temperatures of different layers of 110 kV XLPE cable and its simplified model,by means of Matlab software the cable surface temperature-based computation expression to calculate cable conductor temperature is derived,and the error between the cable conductor temperature calculated by complete thermal circuit model and that by its simplified model are computed theoretically,then the functional relation between the error and the current applied to the cable is given.Meanwhile,a transient temperature rise test of directly buried cable is designed.According to the measured data of cable surface temperature,the temperatures of conductors and insulating layers are calculated by the simplified model,then the comparative analysis on the errors between the temperatures of conductors and insulating layers calculated by the simplified model and the measured temperatures of conductors and insulating layers is performed.Analysis results show that the errors between the cable conductor temperatures calculated by simplified model and the measured cable conductor temperatures are inside the allowable range,thus in engineering application the simplified thermal circuit model can be used to calculate cable conductor temperature by surface temperature of the cable.