Staff photo by Clay Schuldt After a stellar reliability report on the New Ulm’s power system, the Center Street substation, pictured here, will have some preventative maintenance done this year, including replacement of the 69 kV breaker.

NEW ULM — Marked improvements across the board in all measurement standards were reported in the city, according to a 2021 electrical system reliability report.

The New Ulm Public Utilities Commission received the annual electrical system reliability report, Tuesday. Utility Engineer Dan Pirsig said the city’s electrical system had relatively strong year, receiving better scores than other regional electrical providers.

The electrical system is measured on three standards, the System Average Interruption Frequency Index; System Average Interruption Duration Index; and Customer Average Interruption Duration Index.

The SAIFI is the average number of interruptions that a customer would experience per year. Last year, New Ulm’s experienced 0.06 interruptions per customer. The regional SAIFI score for 2021 was 0.6 interruptions per customer.

Utility Engineer Dan Pirsig said this SAIFI score is about as close to zero as possible. It was significantly better than 2020, which had a SAIFI score of 0.14.

The SAIDI is the average outage duration for each customer served. In 2021, New Ulm’s SAIDI score was 4.44 minutes of power outage per person. This was also an improvement from 2020, which had a SAIDI score of 23.99 minutes.

The CAIDI gives the average outage duration that any given customer would experience. The sum duration of outages is divided by the total number of interruptions. New Ulm’s 2021 CAIDI score was 70.25 minutes. This was also an improved score from 2020, which had a CAIDI of 171.8 minutes.

Pirsig said there were only four power interruptions in 2021. The incidents were on May 29, June 6, Sept. 6 and Sept. 26.

The May 29 outage was caused by a lightning strike that impacted three customers. The other three outages were equipment failures. June 6 outage impacted 10 customers and lasted 70 minutes. The Sept. 6 outage impacted 431 customers but also lasted 70 minutes. The Sept. 26 outage lasted the longest at 81 minutes but impacted just 12 customers.

Pirsig said public utilities are being proactive in keeping the system reliable. Cable replacement, tree trimming and pole testing are ongoing projects. In 2022 and 2023 there are significant infrastructure projects planned including a Center Substation bypass; replacement of the 69 kV breaker in the Center Substation and upgrades in the Center Street substation and Fort Ridgely substation.