Derivation of Theoretical Formulas of Sequence Currents on Underground Cable System

A reliable operation of a cable system necessitates an accurate calculation of sequence impedances of the system. It is recently even more important as longer cable lines are being constructed and planned. It has been a common practice that these sequence impedances or currents are measured after the installation and it is difficult to predict these values beforehand with good accuracy. This paper derives theoretical formulas of the sequence currents for a cross-bonded cable and a normal-bonded cable. The accuracy of the proposed formulas is verified through a comparison with EMTP simulations