Transformer winding selection associated with reconfiguration of existing double circuit line to six-phase operation

Conversion of an existing double circuit three-phase 115 kV overhead transmission line to six-phase operation will provide a commercial demonstration of feasibility of high phase order power transmission. An important part of this demonstration is specification of the phase/voltage conversion transformers and requirements to permit single pole switching of the line in a practical manner at minimum cost. Results are presented of engineering studies which led to selection of two delta-wye three-phase transformers at each end, one of each pair with reversed polarity to obtain the 60° shift between phases