United Power, a Colorado co-op that serves Denver suburbs along with more rural and mountainous territory, is taking steps to automate its system that are bringing it closer to a long-sought power industry concept: a self-healing grid.
Through a combination of smart-switching technology, robust fiber-optic communications, and SCADA augmented with an integrated distribution management system,
United Power has automated parts of its system to significantly improve fault management and outage response.
“Today, we have pieces that are fully automated,” says Don McDaniel, the co-op’s engineering manager. “But over time, we will have it fully automated.”
McDaniel is careful to point out that he doesn’t yet describe the system as self-healing. But as they increase automated response capabilities, they’re adopting much of the technology that is part of a true self-healing system.
“They are one co-op that’s really been in the forefront on this,” says David Pinney, NRECA’s software engineering manager.
The idea is to use sensors, smart switches, high-speed communications, and automated control systems to rapidly respond to outages and power interruptions, automatically isolating faulted line sections and routing power to restore service to the greatest number of members in the shortest possible time.
Should a summer storm knock out a section of line, for example, a self-healing system could automatically bring back parts of the circuit by switching into another line and feeding power to the circuit to the point of interruption until the damage is repaired.
An ongoing process
McDaniel notes that United Power’s ongoing automation effort began nearly a decade ago, when the co-op first installed new fault indicators on a 34.5-kV loop serving 5,500 consumers in a mountainous part of their service territory where outages were difficult to resolve.
The indicators were placed on line sections tied to specific substations and fed into algorithms that could assess system data and dictate actions for motor-operated switches. The approach was not fully automated because an operator was still involved, but it improved restoration times in that area.
United Power has continued to press forward with automation. The co-op spends about $750,000 annually, McDaniel says, on automated switch gear, electronic reclosers, communications infrastructure, and related tech.
“As the needs for system upgrades come along, we look at them and try to gauge whether a new piece of switchgear or recloser could benefit from automation,” he says.
The overall effort is driven by a focus on providing extra-high quality service to a region that abuts territory served by the state’s largest investor-owned power utility.
“We can’t beat them on rates. What we can do is provide the best service,” McDaniel says. “This has been our goal for the last 20 years: to be as reliable as possible. This is the way we can stand out.”
The density factor
United Power, based in Brighton, has 90,000 residential and business meters on 5,857 miles of line. It’s a larger cooperative, but it has the smallest service territory in Colorado. The Denver suburbs provide high line density on part of its system, and the oil and gas industry in the less populated part of its territory provide important industrial load.
The density on much of the system makes it easier to invest in some system upgrades, including new loop feeds to provide needed redundancy for power re-rerouting.
Indeed, density plays an important role in the economic case for a self-healing systems, says Robert Harris, NRECA principal engineer for transmission and distribution.
“It usually needs to be built densely enough where you can justify building strong feeder ties,” he says. “And you’ve got enough capacity in another feeder that you can transfer power if needed and save a lot of outage time that way.”
For rural cooperatives with lines that stretch for miles to reach relatively few members, the economics and physical limitations of the lines, which can be voltage limited, make the technology less appealing, Harris notes.
“Many of these systems won’t perform that well on rural lines,” he says.
Pinney says NRECA is working on simulations to help cooperatives with planning when they consider self-healing technology.
“What we’ve been working on recently is what the value of an additional smart switch is,” he says, “and given a distribution circuit with a whole bunch of switches on it, what is the best configuration of switches.”
He notes that this will be even more essential as co-ops integrate more renewables, distributed generation (DG), microgrids, and other features of the evolving grid.
United Power has combined automation with a significant commitment to renewable generation and battery storage. The cooperative has 35 MW of utility-scale solar and an additional 26 MW from more than 4,225 rooftop solar installations among its members. It also has invested in two Tesla battery storage systems providing 18 MWh of power on the co-op system.
Dean Hubbuck, United Power’s chief energy resource officer, says the motive behind the investments has been to provide cost-competitive power to their co-op members.
“We’re focused 100% on our power supply costs,” he says. But down the road, renewables and DG could play a significant role in a more resilient, self-healing system.
“We have all of our large-scale renewables and batteries tied into our SCADA system so they can be completely monitored and dispatched from there,” Hubbuck says. “As we continue to move forward, we’re starting to take a look at behind-the-meter storage; we want to be able to control that, so it can start becoming, in essence, a virtual plant and use it for outage control and reduced costs.”
A 2014 NRECA study, Achieving a Resilient and Agile Grid, said the growth of DG could be a key part of achieving the resiliency and agility necessary for a self-healing grid. Pinney observes that the subsequent years have seen DG become a widespread part of the power landscape.
“Co-ops are very comfortable with it,” he says. “There’s many megawatts of distributed generation out there now.”
Integration and safety
Hardware components of a self-healing grid, like switchgear, are also becoming cheaper and more widely available, says Tom Lovas, NRECA’s transmission and distribution technical liaison.
He says grid resilience has historically focused on bulk transmission because of the large-scale consequences of a significant blackout. But the latest advances in self-healing technology are extending more of that focus down to the distribution level.
“What we’re doing now is taking the technology for reclosers and interruption devices that was used on large transmission systems and bringing them down to useful application at the distribution level,” Lovas says.
As cooperatives adopt more self-healing technology, Pinney says two challenges can be integration and safety. Integrating smart switchgear, other hardware, and new software often proves more complicated than expected, especially if the parts of the system are sourced from different vendors.
Making sure field crews remain safe as automation alters operations protocols is a major priority and can require updating training, he says.
“When switches can operate remotely, everybody has to make sure they’re working in a safe way,” Pinney says. “Historically, if there was no automation, a lineman would have complete control over a local situation. Now they’ve got to make sure everything is locked out and there’s no possibility of a signal coming over the internet and changing what is energized.”
McDaniel says United Power was careful to ensure line crews were kept completely up to date on system automation.
“We’re continually going through training with our guys so they understand it,” he says. With safety the priority, “the crews still have ultimate control” of any section of line they’re working on, he adds. “That was a big concern.”
United Power is using hardware from several vendors, including S&C, Schweitzer, and Cleveland Price. McDaniel says the biggest integration challenge has involved transferring data from the co-op’s geographic information system to the distribution management system, which proved more difficult and time consuming than the co-op anticipated.
Still, he says, United Power continues to look at new technology and software options as it upgrades its system with greater automation and integration of renewables and storage.
“It’s technology. There will never be an end date,” McDaniel says. “We’re going to continue to evolve.”