On circuit breaker failure protection in 61850-based substations

Power system protection is a mission critical task that must be accomplished within the specified time limits so as to maintain the stability, reliability, and safety of the grid. As modern substations embrace the integrated communications and LAN-based substation automation systems using IEC61850 standard, the network latency and reliability issues continue to influence the decision making process to move the critical protection tasks to LAN-based substation automation systems (SAS) and eliminate the laborious and costly copper hard-wiring in the substations. Backup protection functions such as circuit breaker failure (CBF) protection seems to be a good candidate to implement in SAS to gain the operational experience with the new paradigm. CBF protection is a deferred protection function and can tolerate variations in network latency with proper design. This paper explores this application and offers two metrics to assess availability followed by presentation of a case study to illustrate the concepts and this particular application.