UI makes progress in phasing out aging substations

United Illuminating is making significant strides toward culling aging, low-voltage infrastructure from its electric system.
Since 1996, UI, a subsidiary of AVANGRID, Inc. (NYSE: AGR), has retired 34 of 40 low-voltage substations across its service territory. The customer circuits they once served are now part of UI’s newer, more reliable high-voltage system. Low-voltage infrastructure now accounts for just over 5 percent of UI’s overhead (primary) distribution system.
This year, UI expects to substantially complete the decommissioning of its Westville Substation in New Haven, converting the circuits it serves to the higher 13.8 kilovolt standard. That work is underway. Work is also expected to begin later this year to decommission the Gilbert Substation, in New Haven’s Fair Haven neighborhood.
The $6 million Westville project is part of a wider, long-term effort to modernize UI’s electric infrastructure, said John J. Prete, president of Connecticut and Massachusetts operations at Avangrid Networks.
“Over the long term, the ongoing modernization of UI’s infrastructure translates to direct benefits to customers,” Prete said. “The updates make our system less prone to failure and more resilient against storms. The upgraded infrastructure meets current industry standards for safety, provides better power quality — meaning fewer flickering or dim lights — and facilitates restoration if outages occur. It is also helping to ensure the system has the capacity to meet future growth in demand.”
The substations serve as links between the transmission system, which carries electricity across long distances, and the local distribution system of lines, poles and other equipment that carries power to homes and businesses. Each substation serves as a hub for multiple circuits, extending out into neighborhoods and providing power to potentially hundreds of customers.
The low-voltage substations and associated circuits operate at an obsolete standard of 2.4 or 4.16 kilovolts, and they amount to low-voltage “islands” within UI’s higher-voltage network. The aging equipment, as it approaches the end of its useful life, becomes increasingly prone to failure. Because the low-voltage circuits are isolated from the rest of the system, they can’t easily be re-routed to other substations as backup when power is lost due to a storm or similar event.
Each of the decommissioning projects requires UI to work street-by-street to replace or upgrade the power lines, transformers and other components that comprise each circuit. In many cases, new utility poles are also installed, usually stronger and taller than the ones they’re replacing. When that work is complete, customers are switched over to the new, higher-voltage equipment, a process that requires a brief planned outage. Then, the old equipment is taken out of service and the substation is decommissioned.
The Westville project requires conversion of six circuits that serve approximately 3,000 customers, and replacing about 4 miles of overhead lines and 500 utility poles, along with other equipment that needs to be modernized. UI has an outreach program to ensure customers are notified well in advance about planned outages and other project impacts.
UI’s investments in its infrastructure are beginning to show results in terms of reliability. For example, UI customers are experiencing fewer and shorter outages than they did 10 years ago. During the period from 2012-2015, a typical UI customer could expect approximately one outage every two years, down about 20 percent from 10 years before, according to UI’s reliability data.
“UI has a long-term planning process that continuously looks ahead so that we can meet future needs and maintain the high levels of safety and reliability that our customers expect from us,” said Richard J. Reed, vice president for Engineering and Project Excellence at UI. “We want our customers to be able to take it for granted that when they flip the switch, the light will come on. But there’s a lot of planning and work that go into making that happen.”