Assessing Transmission Resilience during Extreme Weather with Outage and Restore Processes

How long is a resilience event in a transmission system?: Metrics and models driven by utility data

“…4) reports typical values for model parameters and duration metrics for North America transmission resilience events. Our previous conference papers [13], [14] extract events and outage and restore processes from transmission system outage data and calculate resilience metrics. These methods are also applied to quantify resilience for the largest events in NERC reports [15], [16].…”

“…To obtain resilience metrics from utility outage data, we first need to automatically extract resilience events and the outage and restore processes for each event. This section explains how to do this based on previous work [8], [13], [14] and establishes the notation needed for the paper.…”

“…The detailed North American outage data from NERC's TADS are the automatic outage data for the following bulk electric system transmission system elements: AC circuits, transformers, AC/DC back-to-back converters, and DC circuits [14]. The data include the outage and restore time to the nearest minute, the initiating cause code for each outage, and the sustaining cause code for sustained outages.…”

“…For each interconnection, the automatic outages are grouped together into resilience events based on the bunching and overlaps of their starting times and durations. We quote from [14] the algorithm used: "Every outage in an event has to either start within five minutes of a previous outage in the event or overlap in duration with at least one previous outage in the event that has a difference in starting time not exceeding one hour. In applying this algorithm, repeated momentary outages of the same element are neglected if they occur within 5 minutes of each other."…”

“…The event starts at time o 1 and ends at time r n . The event duration D E = r n − o 1 can be split into the time to the first restore and the restore duration: (14) This section discusses restore duration, but the corresponding metrics describing event duration are easily obtained from the metrics for restore duration by adding the time to first restore D r1 as in (14). The outage duration D O and time to first restore D r1 are useful metrics, but section V explains that the restore duration D n and the event duration D E suffer from high variability.…”