DUAL 3-PHASE TRANSFORMATION FOR COMPREHENSIVE FAULT ANALYSIS OF A 6 PHASE SYSTEM

Recently there has been a growing interest in the concept of six phase transmission as an alternative to the upgradation of a line, to incre ase the power transfer capability within the existing right of way. In this work the six phase system is treated as two mutually coupled thr ee phase systems and a transformation called dual three phase transfor mation (DTPT) is proposed for the analysis of a six phase system compa red to earlier works on this subject. This method has reduced the numb er of significant combinations to 13, by choosing appropriate referenc e phases and renaming of the conductors, compared to 23 groups. The DT PT sequence networks are obtained in terms of the familiar three phase sequence components avoiding the use of complex ratio or phase shifti ng transformers, mutual inductances and the results completely agree w ith the results of fault analysis using the phase coordinate method. I n a companion paper titled ''Transposition of a six phase transmission line'' it has been established that in the case of conversion of an e xisting double circuit three phase transmission line into a six phase line, a three barrel transposition somethat similar to the transpositi on of a double circuit line is sufficient, in which case there is mutu al coupling only between the two zero sequence components of the two m utually coupled three phase systems which constitute the six phase sys tem. (C) 1997 Elsevier Science S.A.