Calculation & analysis of sequence impedance for parallel multi-circuit cable lines

As affected by electromagnetic coupling, the sequence impedance of parallel multi-circuit cable lines is different from that of single-circuit ones. Based on “conductor-ground” loop, derived from the matrix form of voltage equations, a new algorithm of parameters calculation for multi-circuit cable lines is presented. To consider the influence of metal sheath, the algorithm treats it the same as core conductor. They both form current loops with earth, referred to as “sheath-ground” loop and “core-ground” loop respectively. After a series of matrix operations to the voltage equations of these loops finally the sequence impedance matrix is obtained. The algorithm has taken adequate consideration for the electromagnetic coupling and is applicable to all types of metal sheath grounding schemes. Case study shows that the proposed algorithm has good accuracy. At the end of the paper, an instance of double-circuit cable lines is used to study the feature of parallel multi-circuit cable lines´ parameters.