The influence of negative phase sequence system to differential protection for transformer

The phase relation among side electric currents of internal transformer microcoputer peotection in the primary positive phase sequence system is different from those in the primary negative phase sequence system, this difference was analyzed thoroughly and detailedly by vector diagram, according to the instance of negative phase squence primary system in Gaolong station in Zhuzhou City, the analyzing result indicates that the transformer microcoputer differential peotection runs normally if every side coil winding and secondary wiring pattern establish control word corresponding to the wiring group of transformer, and exact methods solving the problem are carried out, these practically valuable methods may improve on-site jobs.