Substation protection method for missing measurement information of transformer and bus connecting line

In order to solve the problems of protection misoperation and refusing to operate caused by the lack of measurement information in smart substation, a substation protection method which can effectively eliminate the influence of transformer inrush current and bus CT saturation when the measurement information of substation and bus connecting line is missing is proposed. Through the theoretical analysis of current synthesis method based on Kirchhoff current law, it is proved that transformer inrush current and bus CT saturation will lead to the misjudgment of differential protection. Accordingly a new method of station protection is proposed to deal with the lack of measurement information. In order to verify the correctness of the method, taking a typical 220kV substation model as an example, PSCAD / EMTDC electromagnetic transient simulation software is used to simulate and verify different conditions and different types of faults. The results show that the proposed protection method can accurately eliminate the interference of transformer inrush current and bus CT saturation, ensure the correct action of differential protection, and improve the stability of substation when the measurement information is missing.