A method for online relay coordination verification using setting comparison

The distance backup relays configured with fixed settings may lose their pre-determined coordination, and even form a significant threat to system security due to the variety of system operation condition. There are many special temporary operation conditions in the developing power grids of China, which may be not anticipated in the offline relay coordination. Therefore, periodical online verification of relay coordination is highly desirable to detect improper or incorrect settings under the current system state. However, the verification method is also required to perform verification correctly and efficiently in large-scale power grids, whose importance is similar to that of equal-area criterion for transient stability analysis, and eigenvalue methodology for low frequency oscillation analysis. A new verification method using setting comparison is presented, which performs verification more conveniently and efficiently than conventional method using reach point comparison. The application in large-scale power grids demonstrates the availability of the proposed method.