Application of IEC61850-enabled SAS in CBF protection of transformers

Power system protection is a time-critical task that must be accomplished within the specified time limits to maintain the stability, reliability, and safety of the grid. As modern substations embrace integrated communications using the IEC61850 standard, network latency and reliability issues continue to influence decisions regarding moving the critical protection tasks to LAN-based substation automation systems (SAS), thus eliminating the laborious and costly copper hard-wiring in the substations. Backup protection functions, such as circuit breaker failure (CBF) protection, have appeared as good candidates for implementation in SAS to gain operational experience with the new paradigm. CBF protection, a time-delayed protection function, can tolerate variations in network latency when designed properly. Because transformers are the most critical and expensive pieces of substation equipment, evaluating transformer bay CBFs specifically is crucial. This paper categorizes transformer protection functions and explores the application of CBF protection in SAS using GOOSE messaging specifically in transformer bays. A typical transformer bay is investigated as a case study.