Hidden failures in equipment are those failures which occur at random and that do not lead to any discernible change in the state of the network and, therefore, remain undetected. Although hidden failures can occur in any equipment, the hidden failures in protective equipment have attracted a good deal of attention in recent years. Admittedly these failures are rare but, when the power system is stressed, their effects on the power system can be catastrophic. This paper examines the mechanisms of hidden failures of the protection system, their role in major power system disturbances, and concludes with lessons learned from an examination of past system blackouts.
['Arun G. Phadke']
Hidden failures in electric power systems