Hidden failures in protection systems and their impact on wide-area disturbances

This paper explores hidden failures in protection systems, which have been identified as key contributors in the cascading of power system wide-area disturbances. The original definition of hidden failure, which is a failure that remains undetected and is uncovered by another system event, is included as are the developments of hidden failure sequence of events and a methodology for hidden failure identification. This method is based on protection element functionality defects (PEFD). Hidden failures modes are developed based on the relaying implementation for primary protection, back-up protection and special protection systems. Wide-area disturbances based on North American Reliability Council (NERC) reports are analyzed and hidden failures are identified employing the developed methodology. The mechanisms in the wide-area disturbances are summarized. Regions of vulnerability and areas of consequence are important concepts that identify the critical elements from the point of view of hidden failures.