Investigation on Circulation Current Calculation and Grounding Methods of Multi-circuit Cables

This paper presents the precise evaluation of the electrical characteristics of multi-circuit cables. For this purpose, the series impedance matrix and the parallel admittance matrix per unit length of the multi-circuit cables are derived based on the multi-conductor theory. By comparing the π-equivalent circuit and the non-decoupling model, the node admittance matrix is deduced to construct the voltage-current relationship between the head and tail ends. Through symmetrical and asymmetrical node admittance matrix cascade formula analysis, the matrix solution method for steady-state calculation of the multi-circuit cables is derived. The matrix is used to investigate grounding methods of the multi-circuit cables. A typical 220 kV cable line is used in the simulation case. The results show that the induced voltage of the metal sheath is the lowest when the two ends of the cable are grounded, but the circulating current of the metal sheath is the largest. The induced voltage of the metal sheath can rise up to 332.32V and circulating current of the metal sheath can have a maximum value of 1246.63 A.