ANALYSIS OF THE FAULTS INVOLVING ADJACENT CONDUCTORS OF A 6-PHASE TRANSMISSION-LINE TOGETHER WITH A MODELING OF THE PHASE CONVERSION TRANSFORMER

In a bulk power transmission system the amount of power transfer can b e increased by converting the widely used three-phase double-circuit l ines into six-phase single-circuit lines instead of upgrading the tran smission voltage. In this conversion process only a phase conversion t ransformer at each end of the line is required while the existing cond uctors, towers and corridors of three-phase lines can be used intact. However, this conversion will have an effect on the system fault curre nts and fault levels. The well-known symmetrical component method is s uitable for fault analysis in a three-phase system, but it has been fo und unsuitable for analysing the practical faults on a six-phase line and for modelling the phase conversion transformer. This paper illustr ates the way the phase conversion transformer has been incorporated in the six-phase line fault modelling and also presents a new applicatio n of the straightforward loop current method by using it to determine the currents and fault MVA corresponding to the common and practical f aults on a 132 kV six-phase line. The same method has also been applie d to the fault analysis of a 132 kV and a 230 kV three-phase line and the results are compared with those for the six-phase line.