Ameren, an investor-owned utility operating in Illinois and Missouri, is one of the first utilities in the U.S. to trial a private LTE network. Using spectrum in the 900 MHz band, Ameren was able to replace 20 separate networks with just one LTE network.
The trial used a tower in Peoria and an office building in St. Louis. Ameren’s partner Nokia installed eNodeBs in St. Louis, Champaign and Peoria, with roughly 18 field devices connected via premise equipment for testing. Nokia used its Airscale remote radio heads and Flexi Zone Multiband Micro base transceiver stations.
In some of Ameren’s substations, 911/voice calls, security systems and SCADA (supervisory control and data acquisition) were each using different radios before the trial. Now they are all using LTE. “We were using three different methods of communication in a single substation, so one robust technology really helps,” said John Hughes, Ameren’s director of network engineering,
He added that the devices which run Ameren’s automated line and load management platform are also more efficient with LTE. He was able to eliminate gateways and get the devices to communicate with one another directly across the network. “The performance was more than adequate to meet the switching needs,” he said. This direct communication is going to make it faster to roll out the equipment, he said, which should benefit Ameren’s customers.
Nokia and Ameren trialed 14 use cases in all, and said they could have come up with even more. The Utility and Technology Council recognized the trial with an award for “exceeding performance and scalability expectations.”
Hughes sees an even larger benefit. “The biggest benefit is just the consolidation or convergence into a singular standard,” he said. “We all know that going forward pretty much every vendor is adopting an LTE footprint.” Nonetheless, Ameren does not want to rely on public carrier networks. “When it comes to managing grid, recoverability, the time to restore ... we want that private, we want to manage and own that capability and not be dependent on a third party,” Hughes said.
Liana Ault, energy innovation lead at Nokia, said there were some requirements that the carriers were unable to fulfill for Ameren. "There were specific needs that we had that the carriers could not meet from a technical perspective or could not meet from a business perspective," she said. She added that carrier backhaul is still important to Ameren's private network, and Hughes said failover to public carrier worked flawlessly in the tests.
Ameren is a good candidate for private LTE because it already has a growing fiber optic backbone based on an MPLS network. “We want that capability extended all the way to the end through the private LTE,” Hughes said. “We want the encryption all the way to the end.”
That sounds expensive, and Hughes admits that it is. “It’s not two years and it’s paid for,” he said. “It’s going to be over a life of these assets. I think you are probably going to see people bringing it out between seven and ten years.” For Ameren, full-scale deployment of private LTE is not a done deal. “We are in the process of justifying our benefit and going-forward approach,” said Hughes. “That is still a work in progress.”
One justification is the cost of operating a digital grid, which could create increased reliance on public carrier networks. “Having a digital grid is a foundational capability for driving efficiency and adopting renewables and two-way flow of energy,” said Hughes. “That digital grid is driving a lot more touch points and data points. … public carrier is going to get extremely expensive. There is an ongoing operating cost that gets compounded.”
Private LTE may have more predictable costs, and trials like this one are helping utilities reach a better understanding of those costs. Nokia's Ault said private LTE can create the need for additional civil work, added tasks like SIM card management, and new training for RF engineers. Companies may need to hire new people to operate private LTE networks; Hughes said Ameren has been hiring network engineers with carrier backgrounds.
Ault noted that private LTE networks can also bring new cost savings, including a reduction in truck rolls, which will cut expenditures as well as a utility’s carbon footprint. “I would fully anticipate that some of the power utilities will start measuring those types of impacts as well,” she said.
Spectrum considerations
Hughes said the 900 MHz band was the best choice based on availability, cost and propagation. The team considered WiMAX and AT&T’s 2.3 GHz spectrum, but both of those became unavailable. They also thought about CBRS, but Hughes said that would probably require Ameren to bid for priority access licenses and to build more towers, since CBRS does not propagate as far as 900 MHz. Ameren leases 900 MHz spectrum from Anterix, a company that has amassed large swaths of this spectrum and successfully lobbied the FCC to enable broadband in the band.
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5G may create new opportunities for utilities to deploy private wireless in other spectrum bands. Ault said that most companies she talks to are currently exploring private networks for the shorter-range distribution grid versus the longer-range transmission grid, but she thinks that could change with 5G. Hughes agreed that private networks will definitely have a place in transmission networks, especially as utilities increase their reliance on sensors, drones, and LIDAR.