Reliabilty of protection systems (what are the real concerns)

Protection Systems have a significant role in maintaining the stability and reliability of the electric power grid. Their optimal performance plays a vital role and becomes more critical when the power system is operating near its limits. Protection Systems are used to detect and isolate faults or to arrest adverse conditions that occur on the grid. Subsequently, misoperation of these systems must be kept to a minimum. This paper discusses protection applications and reliability considerations, and methods such as Synchrophasor monitoring of system conditions that can be incorporated into protection schemes to reduce problems stemming from a variety of hidden failure modes and increase the effectiveness and reliability of Protection Systems. The impact of Protection System failures on dependability and security is discussed. Failure modes initiated by Calculation of Settings and Modeling Errors, Firmware issues, and Hardware failures will be analyzed. The various components of the Protection System are described and plausible failures of these components are presented. The use of separate but equivalent (redundant) protection systems is presented to illustrate methods that could increase reliability of the protection systems. This includes a discussion concerning same or different manufacture of protective relays. The probabilities of these failure modes will be presented. The effect of the new NERC guidelines on protection system redundancy is evaluated.