Evaluation of uncertainties in the Back-up Protection Expert System for a transmission network

The method described in the paper evaluates the unavoidable uncertainties associated with the tripping decisions generated by a Back-up Protection Expert System (BPES). Two certainty factors including the certainty factor (CF) of a power system component containing a fault and the certainty factor of a protection relay or element maloperating (CFM) are introduced. An example is included and is used to demonstrate how the proposed uncertainty evaluation method was integrated into the BPES and how it is used to evaluate the uncertainties associated with a conclusion derived by the BPES for a fault on the south western part of the UK National Grid System.