Great River Energy uses 10 industry-accepted reliability indices to measure transmission reliability to its 28 member-owner cooperatives. New records were set for eight of those measurement in 2021, resulting in one of the best years for Great River Energy’s reliability on record.
“Unusually mild weather in the state and our investments in the grid contributed to an excellent year in 2021,” said Keith Kantola, senior engineer at Great River Energy.
There are two types of outages: momentary outages that last less than one minute and sustained outages that last one minute or more. Reliability indices are used to measure the impact of those outages to substations and member-consumers.
Momentary outage reliability has improved significantly during Great River Energy’s 23-year history. Total momentary outages to member-owner distribution substations in 2021 was 39% better than the 10-year average (a new record), and the total momentary outages to member-consumers measurement was 35% better (also a new record). Great River Energy’s goal is to limit the number of momentary outages to member-consumers to 2.5 per year or less. The cooperative recorded less than 1 momentary outage in 2021.
“Lightning is the number one cause of momentary outages,” Kantola said. “Great River Energy has been investing in lightning mitigation like arrestors and ground fault neutralizers and rebuilding lines to new design standards that include shield wires. We’re seeing those investments pay dividends on our momentary outage reliability metrics.”
Impact of severe weather
It was a turbulent year nationwide for severe weather. According to the National Oceanic and Atmospheric Administration, there were 20 weather or climate disaster events in the U.S. in 2021 with an average loss of $1 billion per event. Southern Minnesota experienced a rare “derecho” wind storm on Dec. 15 that spawned 20 tornadoes (the first confirmed December tornadoes in state history). As temperatures fell, the thunderstorms brought ice, snow and damaging winds of more than 75 miles per hour.
Despite this event, the score for Great River Energy’s total sustained outages to member-owner distribution substations was 26% better than the 10-year average (a new record). The total sustained outages to member-consumers measurement was 27% better (also a new record). Great River Energy’s goal is to limit the number of sustained outages to member-consumers to 0.67 per year or less. The cooperative recorded 0.28 in 2021.
Impact to members
Member-consumers experienced 13.38 minutes of outage time in 2021, less than half of Great River Energy’s goal of 30 minutes per year or less.
“Severe weather is the leading cause of outage time,” Kantola said. “We currently have a resiliency effort in place to look at Minnesota’s various weather and climate threats and the risks they pose to our assets so we can better mitigate the impact of these severe weather events.”