OKLAHOMA CITY – Metrics employed to measure the reliability of service provided by six regulated electric utilities in this state show that Public Service Co. of Oklahoma has been “consistent” over the past five years, with fewer power outages of shorter duration than other electricity providers.
That conclusion can be found in the Oklahoma Corporation Commission 2020 “Reliability Scorecard” issued this month.
In another matter, PSO’s application to reduce its fuel charges through the end of this year was approved by the Corporation Commission and went into effect at the beginning of May, said Stan Whiteford of PSO Corporate Communications.
2 BASIC GAUGES OF RELIABILITY
The commission reported it relies on two basic gauges of electric service reliability “to gain insights regarding how consistently” six of the state’s regulated electric utility systems (including PSO and OG&E) “are providing uninterrupted energy.” Those gauges are:
• System Average Interruption Frequency Index (SAIFI). This is the average number of sustained interruptions (5 minutes or more of zero voltage per incident) per consumer during a year.
• System Average Interruption Duration Index (SAIDI). This is the average duration of interruptions per consumer during a particular year.
The two biggest regulated electric utilities in this state are PSO and OG&E. Public Service Co. – which serves at least 37 cities and towns in southwest Oklaho- ma, including Lawton, Altus, Cache, Duncan, Elgin and Fletcher – reported 553,971 customers at year’s end 2019. Oklahoma Gas & Electric reported 781,764 customers at the close of 2019.
Among all of the electric utilities regulated by the Corporation Commission in 2019, Oklahoma electric customers were without power approximately 1.31 times, on average. In comparison, SAIFI data show that in 2019 PSO customers were without power an average of 1.15 times.
Over the past five years, Oklahoma customers served by a regulated electric utility experienced 1.161 power outages each year, on average. For PSO customers, that rate was lower: 1.104.
The SAIDI measurement calculated that customers of Oklahoma’s regulated electric utilities were without power for an average of 132.59 minutes last year. In comparison, PSO customers “were without power for the shortest time” in 2019: an average of 115.91 minutes, the Corporation Commission found.
And over the past five years, the average time that a customer of the six subject utilities was without power totaled 132.28 minutes (2.20 hours). In comparison, for PSO customers that total was 107.47 minutes (1.79 hours).
STORMS LAST YEAR HAD ‘NOTABLE IMPACT’
Last year several “storm events” had “a notable impact to SAIDI” for PSO customers, the company reported. Among them were thunderstorms on May 18, 2019, that affected the Law- ton area, and severe weather in the Lawton area on June 15 and again June 19, 2019. Consequently:
• PSO’s 44,329 Lawton customers were without power on average 1.268 times in 2019, for an average of 123.21 minutes, company records reflect.
• The utility’s 5,037 customers in Duncan lost power an average of 2.104 times last year, for an average of 372.64 minutes.
• PSO’s 5,963 customers in Hobart were without power on average 2.696 times in 2019, for an average of 176.73 minutes.
• PSO’s 4,320 customers in Tipton were without power on average 1.087 times last year, for an average of 86.50 minutes.
SW OKLAHOMA HAD 7 OF PSO’S WORST PERFORMING CIRCUITS
PSO also identified 5% of its “worst performing” circuits last year.
Of 786 total circuits in PSO’s service territory, southwest Oklahoma accounted for seven of the utility’s 39 worst in 2019, as ranked by their average duration of interruptions per consumer, company records show. Those seven serve customers in Duncan, Grandfield, Waurika and Terral.
• The leading offender among the 39 worst was a Duncan Northwest circuit that serves 192 customers. It averaged 14.7 outages last year for an average duration of 1,678 minutes, or almost 28 hours each, records reflect.
• A Waurika circuit that serves 22 customers averaged 2.09 outages last year for an average duration of 31 hours each.
• A circuit that serves 247 customers in Terral averaged 2.04 power outages in 2019 that lasted for almost 30 hours each.
• Another Duncan Northwest circuit, which serves 453 customers, averaged 3.88 outages last year for an average duration of 14.6 hours each.
• The Duncan Bois d’Arc circuit, which serves 168 customers, averaged 3.42 power outages last year, each of which lasted for an average of almost 13 hours.
• A Waurika circuit that serves 224 customers logged an average of 5.098 power outages in 2019 that had an average duration of nearly 11 hours each.
• And a circuit that serves 598 customers in Grandfield recorded an average of 3.09 outages last year, each of which lasted for an average of more than 101⁄2 hours.
CORRECTIVE MEASURES UNDERWAY BY COMPANY
“Fortunately, I believe the circumstances – beyond weather – that led to those circuits being among the 5% worst performing in 2019 have largely been resolved, or are well on their way to being resolved,” Whiteford said.
“Aside from weather,” he said, “equipment issues and incidents involving animals were the primary factors in the performance of those circuits.”
PSO has taken “several proactive steps to address the causes behind the outages impacting customers” who are served by the company’s Terral, Waurika, Duncan Northwest, Duncan Bois D
Arc, and Grandfield substations, Whiteford said.
Following is a list of measures “we’ve taken to improve the reliability of electric service to customers in those areas,” he said.
• A transformer failure at PSO’s Waurika substation contributed to extended outages at both Waurika and Terral. “This single event was the primary factor contributing to that circuit’s 2019 performance numbers,” Whiteford said. PSO has provided a temporary substation transformer for this location “and is in the process of replacing the failed transformer and associated equipment,” he said.
• Duncan Bois D’Arc and Duncan Northwest have been switched to a different source to reduce line exposure and provide more reliable electric service for PSO customers in that area.
• Grandfield “has been patrolled and necessary repairs are in progress, including upgrading of several structures along this line,” Whiteford said.
All of the circuits on the “worst-performing” list will be inspected this year, and the appropriate maintenance as indicated by those inspections will be performed, Whiteford said.