By Sarah Wernette, MRO Senior Systems Protection Engineer
Midwest Reliability Organization (MRO) has released two updated white papers on protection system misoperations and their impact on reliability of the regional bulk power system. Since original publication in 2016 and 2017, the MRO region expanded, prompting a re-evaluation of the earlier analysis. While the overall conclusions remain largely unchanged, the updated papers incorporate additional years of data and a broader geographic scope.
Published by MRO’s Protective Relay Subgroup (PRS), with support from staff, the white papers examine protection system misoperations and the schemes and failure modes with the greatest operational impact on the power grid. Misoperations involving overcurrent and directional comparison blocking schemes are often tied to external faults and are more likely to result in multiple outages than those occurring under non-fault conditions.
The updates highlight breaker failure and bus differential schemes, where unnecessary operations or failures to operate can significantly increase event severity and, in some cases, lead to outcomes that meet NERC event analysis thresholds. The findings reinforce that reducing misoperations in these systems can materially lower overall system risk.
A recurring theme across both papers is the role of human performance and commissioning practices. Many of the identified mitigation strategies focus on improving settings development, design review, and testing. The papers also emphasize the importance of adequate commissioning time, noting that compressed construction schedules can contribute to misoperations if protection schemes are not thoroughly validated before being placed in service. Building on these findings, the PRS is continuing to focus on human performance, with additional guidance expected later this year.
The content is intended for engineers, technicians, and other industry professionals involved in the design, installation, testing, and maintenance of protection systems, as well as those interested in reliability performance and event analysis.
MRO extends its appreciation to members of the PRS for their time and technical contributions to this effort.
Details on PRS quarterly meetings (open to the public) are on our website here. Follow the links below to download the whitepapers:
Protection System Misoperations Phase 1 | Protection System Misoperations Phase 2