Abstract: To guarantee the operation correctness of switching equipment during self healing control of power grid, it is necessary to extent and set up CILO based on IEC 61850, and to design wide area security defense system. Firstly, the realizing condition and basis of self healing function is discussed, then the realization of online interlocking mechanism in substation layer and wide area protection layer during operation of self healing control switching equipment is studied in detail, and wide area locking logic is generated by calculation of locking security index in wide area protection layer.