Sequence impedance computation by means of multiconductor method

The computation of sequence impedances is a very important topic for insulated cable systems chiefly in HV and EHV levels. Both in planning and operating activities, power flow and short circuit studies are always based on the knowledge of sequence impedances. Furthermore, the correct behaviour of network protection (mainly distance relays) is strictly depending upon their correct settings which are based on positive-negative and zero sequence impedances. Moreover in the planning phase of a new cable link power flow and short circuit studies are always based on the knowledge of sequence impedances. This highlights the importance of using reliable procedures in order to compute these impedances since, up to now, their computations are based on simplified formulae. One of the authors has already presented some papers [1, 2, 3] which allow studying cable systems by means of the multiconductor cell analysis (MCA). This method considers the cable system in its real asymmetry without simplified and approximated hypotheses. One of the advantages of the MCA is the possibility to supply the cable system with three sequence voltage phasors and to compute the ratios between voltage and current phasors for each phase.