UI's infrastructure investments help boost system reliability

The United Illuminating Company, subsidiary of AVANGRID, Inc. (NYSE: AGR), continues to invest in a modern, reliable electric system, and customers are seeing benefits in the form of fewer and shorter outages.

The company’s reliability figures show that the frequency and duration of outages have both trended downward in the last decade, a period during which UI made significant upgrades to its electric system.

“UI has been doing a lot of work to add value to the service it provides to its customers,” said John J. Prete, president of AVANGRID’s Connecticut and Massachusetts operations. “From introducing new technologies to replacing aging infrastructure, this work is being done with customers in mind, and that’s starting to show in the numbers.”

On average, a customer had about a 54%  likelihood of experiencing a power interruption 5 minutes or longer during any given year between 2012 and 2015, accordingto UI’s reliability data (see “Measuring Reliability,” below). That’s about one outage every two years on average, and it’s down from about 67% during the 2006-09 period.

When customers did lose power, the interruptions typically lasted 92 minutes in the 2012-15 period, compared with 100 minutes in 2006-09.

North Haven First Selectman Mike Freda said reliability is a key concern for residents and businesses in his community. He noted that about 30% of residents have septic systems or wells that run on electricity.

“Lengthy power outages adversely impact their quality of life,” he said.

Freda said UI’s recent work to prevent vegetation from encroaching on UI’s overhead power lines has helped to “dramatically reduce” power outages during storms in his town.

Upgrading the Electric System

UI has been engaged in a variety of projects to modernize its electric system and ensure it can continue to provide safe, reliable electric service to customers. These include:

  • In 1996, UI started a project to retire 40 old, low-voltage substations and rebuild the associated distribution infrastructure — including overhead lines, transformers and in some cases poles — so that they can interconnect with the surrounding high-voltage system, facilitating restoration during outage events. So far, 34 substations have been removed from service, with the 63-year-old Westville Substation scheduled for decommissioning and conversion this year. Nearly 95 percent of UI’s overhead system and more than 97 percent of its underground infrastructure now operate on the modern, high-voltage standard.

  • After Tropical Storm Irene in 2011 and Super Storm Sandy in 2012, UI invested $15 million to provide short-term protection of seven coastal substations against flooding. These measures included installing pumps, back-up generators and physical barriers to keep water from entering these critical links between the transmission and distribution systems. Loss of a substation could affect service to thousands of customers for extended periods.

  • In 2014, UI began to implement new, state-approved vegetation management standards that seek to create a wider buffer between overhead lines and nearby vegetation. UI estimates that during storms, trees within 8 feet of utility lines are to blame for about two-thirds of tree-related outages.

  • In 2013, UI completed a 12-year program to replace all of the paper-insulated lead cable in its system, which was responsible for about 15 percent of customer outages in 2001, with new, rubber-coated cable that’s significantly less prone to failure.

  • UI is implementing new systems to modernize storm-response operations. These technologies will give restoration planners a much more detailed picture of storm damage, so they can deploy crews and other resources more efficiently, provide more information to customers, and restore service more quickly.

  • Since 2013, UI has been an active participant in the North Atlantic Mutual Assistance Group, a regional consortium of electric utilities that coordinates sending crews and equipment to help with restoration efforts after storms and similar events.

“Clearly, the work we’ve been doing is contributing to our ability to provide dependable electric service that’s there when you flip a switch,” said Joseph D. Thomas, UI’s vice president for Electric System Operations. “Our field and office employees work hard and make a commitment to providing quality customer service each and every day. Their efforts continuously improve on our system designs, maintenance practices and new and efficient operating approaches, yielding positive reliability results.”

Measuring Reliability

UI uses three common industry metrics to track reliability: SAIFI (System Average Interruption Frequency Index), the average frequency of outages a customer can expect in a given year; SAIDI (System Average Interruption Duration Index), the duration of outages, in minutes, averaged across all customers; and CAIDI (Customer Average Interruption Duration Index), the average duration of outages, in minutes, for those customers who actually experience outages.

All three indices, tracked on four-year rolling averages, show improvement in recent years, and UI consistently ranks in the top 25 percent for reliability, industry-wide.

Company officials noted that even though the data exclude outages during major storms, weather can still have a significant impact on the reliability figures. For example, major storms can damage or weaken trees which can trigger outages weeks or months later, causing outage numbers to spike during the post-storm period. Similarly, outage numbers may dip during years that are relatively uneventful, weather-wise.