A method is recommended for calculating the additional positive sequence impedance in the same direction suitable for all kinds of fault with the use of the six-sequence component. With the proposed method an analysis is made on the feasibility and potential economic benefits of quasi-three-phase (QTP) operation. An example is studied with actual engineering parameters to verify the advantages of QTP operation. Then the specific decision-making process of improved tripping and reclosing strategy is elaborated. The strategy makes classified optimization according to the number of namesake fault phases

minimizing removal and reducing reclosing requirements on the premise of satisfying QTP operation. Analysis and comparison with the traditional tripping and reclosing strategy is made with the above engineering parameters. It is proved that the proposed strategy is able to provide favorable conditions for the application of QTP operation. This work is supported by National Natural Science Foundation of China (No. 51277058).