Transmission and Generation Misoperations During an Extreme Weather Event
In October of 2016, Hurricane Matthew struck the southeast United States. By the time the storm had reached South and North Carolina its wind speeds were severely weakened.. However, Matthew produced such a large quantity of rain that several flooding records were broken in North and South Carolina. The severe flooding coupled with high winds caused widespread outages to the electric power system in both North and South Carolina. During the storm, two large generation facilities in the Duke Energy tripped out due to undervoltage conditions on the low side bus of those generation facilities. The root cause of these generation trips was older electromechanical transmission line protection systems failing to operate during faulted conditions. In both instances the faults existed on the transmission system for several seconds before remote backup protection was able to clear the faults. This delay in tripping coupled with the weakened power system led to the long term undervoltage and subsequent undervoltage trip the generation facilities experienced. This paper and presentation will outline each event in detail and provide the conclusions of the cause analysis of each event. The similarities of the events will then be discussed, specifically focusing on the use of electromechanical relays as compared to replacement with microprocessor relays and the importance of single point of vulnerability analysis.