Analysis of the faults involving adjacent conductors of a six-phase transmission line together with a modelling of the phase conversion transformer

Abstract

Abstract In a bulk power transmission system the amount of power transfer can be increased by converting the widely used three-phase double-circuit lines into six-phase single-circuit lines instead of upgrading the transmission voltage. In this conversion process only a phase conversion transformer at each end of the line is required while the existing conductors, towers and corridors of three-phase lines can be used intact. However, this conversion will have an effect on the system fault currents and fault levels. The well-known symmetrical component method is suitable for fault analysis in a three-phase system, but it has been found unsuitable for analysing the practical faults on a six-phase line and for modelling the phase conversion transformer. This paper illustrates the way the phase conversion transformer has been incorporated in the six-phase line fault modelling and also presents a new application of the straightforward loop current method by using it to determine the currents and fault MVA corresponding to the common and practical faults on a 132 kV six-phase line. The same method has also been applied 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.