Diagnosis performance assessment of the secondary protection for a 68‐bus power system

Summary This article concerns the assessment of diagnosis performance of a recently developed secondary protection (SP) applied to the IEEE 16‐machine 68‐bus test system subject to primary protection (PP) misoperations on transmission short circuit faults. A PP may fail to trip or falsely trip a line. Such PP misoperations have been known to be a main culprit of modern day blackouts. The function of the SP is to take a timely corrective action before a misoperation causes instability through on‐line diagnosis and stability assessment. Its feasibility hinges on the effective utilization of networked advanced digital relays. We have recently built a full set of diagnosis filters with sensor‐localized dynamic transmission circuit models representative of all anticipated line contingencies in the 68‐bus system and computed the postfault stability regions for the contingencies. The sensor‐localized circuit partition drastically reduces the processing and communication complexity of diagnosis. This work evaluates the diagnosis performance of the SP's multiple‐model filters (MMF) using hybrid simulations driven by both randomly generated discrete events of PP misoperations and the governing dynamics of rotor angles of the 16 interconnected synchronous generators. Of the 1000 independent replications of simulation conditioned on each type of randomly generated misoperations, a 98% correct diagnosis rate is achieved. Each diagnosis conclusion is reached by the SP's MMF scheme within a few tens of a millisecond from the onset of a PP misoperation following a random transmission short circuit fault. This suggests that the SP can circumvent a large percentage of potential blackouts cost‐effectively.