Abstract: This paper discusses and analyzes the key points which may be easily ignored in the selection and calculation of low-voltage power cable, points out the relation between DC resistance and AC resistance in the calculation of conductor impedance, and emphasizes that the cable cross-section shall be verified by electrical protection. Taking the widely used XLPE insulated cable as an example, this paper specifies the maximum conductor temperatures and the recommended actual working temperature. This paper also introduces a calculation method for the assumed temperature in case of short circuit of conductor, and gives the trends of the calculated assumed temperature of conductor and the relevant resistances in case of short circuit of low-voltage power cables.

Key words: cable and conductor , DC resistance and AC resistance of conductor , maximum allowable temperature of conductor , actual working temperature of conductor , calculation of assumed temperature in case of short circuit of conductor , resistance when the conductor is short circuited , short circuit current at the end of low-voltage circuit