San Diego Gas & Electric starts private LTE build with CBRS spectrum

As energy sources become more diverse, utilities are turning to private LTE for connectivity. The reduction in carbon emissions attributed to this photovoltaic system is equivalent to planting 1,456 trees each year. (SDG&E)

A number of U.S. utilities are trialing private LTE, but San Diego Gas & Electric is one of the first to actually start deploying a network. The utility made its intentions clear by spending $21 million to acquire three Priority Access Licenses (PALs) in the recent CBRS auction. Now, SDG&E is deploying its first live sites with plans to evaluate their performance before beginning a larger rollout.

The utility envisions a number of use cases for its private LTE network, including metering, faulted circuit indication, mission critical push-to-talk and supervisory control and data acquisition (SCADA). SDG&E also uses wireless communication for its state-mandated wildfire mitigation plan, which includes a system to neutralize fallen power lines before they can start fires. The utility developed this system using proprietary communications infrastructure, but now wants to use private LTE (PLTE) to scale it. 

"A key driver for our PLTE system is to provide wireless communications to enable our Falling Conductor Protection (FCP) system," said Omar Zevallos, manager of network technologies for SDG&E. "This system relies on low latency communications to detect a powerline that has failed and de-energize it before it comes in contact with the ground. PLTE meets our technical and operational requirements to serve this critical system. We also see this system helping us more effectively serve the growing renewable power and energy storage systems connected to our grid, as well as meeting growing demands for electric vehicle charging and other new loads.” 

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SDG&E used Nokia's private LTE solution for its initial tests and is continuing to work with the vendor as it rolls out the first live sites. The company has not publicly committed to one vendor for the longer term project, nor has it named its Spectrum Access System provider. Spectrum Access Systems use sensors and software to dynamically clear CBRS spectrum for incumbent users when needed. In San Diego the U.S. Navy is an incumbent user of the CBRS spectrum.

Utilities and private wireless

Program manager Burns & McDonnell will be responsible for engineering, procurement, construction and supervision of contractors. The firm expects the build to be a multi-year project that will utilize multiple spectrum bands over time. Overseeing the project is Burns & McDonnell's Bruce Albright, the company's 5G solutions manager. Albright pioneered private LTE in the utility industry while working at Southern Linc, where he oversaw the first greenfield LTE network built by a U.S. utility. The experience turned him into an LTE evangelist within the industry.

"Private LTE really does change the landscape for utilities that go down that path," Albright said. "It helps us as a whole, as a country, as a community, to have that reliability and sustainability of our power systems." Albright said that once an LTE network is in place, communities discover unforeseen use cases, such as connected sensors to detect gun shots or monitor street lights. He said sensors are also important as the power grid becomes more distributed and bi-directional.

"With everything from solar to wind power and other things that are coming into the network, we're now seeing a two-way flow from homes back onto the power grid, and in order to control that they have to be able to communicate and do a lot of things that they didn't need to do in the past, so this is requiring many more sensors and a lot more communications," Albright said. "Any communications needs you have can be serviced by a private LTE network. So now you're not building multiple systems every time you need a new way to communicate; you have a foundational communication system that you can build on and grow with."

Albright sees SDG&E and Ameren as the current utility trailblazers in the private LTE space. He said that for SDG&E, the need for low latency was a decisive factor in the decision to build a private LTE network. "With LTE you can get the low latency, you can kind of push things to the edge to make decisions faster out at the edge of your network ... I think that was really their driving motivation that started them down this path," he said.

Despite his title (5G solutions manger), Albright does not currently see a role for 5G in utility networks. "I don't find anything that utilities need from a 5G deployment," he said. "5G requires a lot of spectrum and capacity."

Even wide-scale deployment of LTE private networks will take some time for the utility industry. "They have to make sure they get it right," Albright said. "They can't make missteps along the way, so they do move extremely slowly, but once they make all the decisions and after Phase 1 you will see an explosion of quickness because then they want everything done right away."