High-voltage generation reserves cost more than would portable, small-scale units to keep critical services on line during a major power outage.
Can You Hear Me Now?
Cellular carriers challenge mesh-network dominance.
“Which choice is best depends on the utility use case,” said Narasimha Chari, chief technology officer with vendor Tropos Networks. “Going with a public carrier can be the fastest way to get an AMI project completed. But for distribution automation, cellular isn’t really an option. It doesn’t give you the low latency you need.”
SmartSynch and the wireless carriers, however, say such arguments are based on misconceptions and outdated information; that wireless networks have dramatically expanded their coverage in recent years, and nearly ubiquitous 2G data networks are perfectly capable of providing response rates below 800 milliseconds, as utilities say they need.
“We’ve spent millions of dollars testing the latency issue,” said SmartSynch Chief Marketing Officer Campbell McCool. “It’s easy to claim there’s a latency problem, but it’s absolutely incorrect. Latency is actually lower with cellular than it is with mesh networks.”
So the experience of the average cell phone user doesn’t accurately represent what public wireless networks can do for stationary utility systems, according to McCool. If mission-critical systems need things like low latency, guaranteed coverage and bandwidth priority, then public carriers can provide it under standardized service level agreements (SLA).
Will such SLAs explode the costs for utilities? The answer depends on whom you ask, but it’s fair to say that if they do, then public carriers won’t get the business. Utilities will board the cellular bus only if it makes more sense than building out their own mesh networks.
If it’s true that public wireless networks can provide the same level of service that mesh networks can deliver, then cost becomes the only question that really matters. Technology aside, the basic difference between the two platforms is that in most cases a private network is owned by the utility as a capital asset—usually subject to base-rate financial returns—while public network service represents an operating expense. Building a network is a much larger capital cost, but over time cellular service costs add up.
“It’s definitely a cost utilities aren’t paying today,” said Mark Munday, president and CEO of metering company Elster Solutions N.A., which designs its systems to be network-agnostic; Elster sells meters that operate on mesh networks, and also it signed an agreement in mid-December to integrate AT&T connectivity into its AMI products. “Utilities that already have private networks in place want to leverage that asset rather than adding a monthly charge. That makes sense, but sometimes private radio is narrowband and you need more bandwidth. We believe in matching the right technology to the applications and preferences of the utility.”
Only experience can prove whether public cellular networks are the right technology for mission-critical utility applications, as SmartSynch and the wireless carriers say they are. Time is running short, however, because once utilities build out mesh networks to transport their smart grid data, cellular might be locked out.
“We’re all trying to capture the market,” McCool said. “There’s no question about that. And utilities that have spent tens of millions of ratepayer dollars to start building out an RF mesh network aren’t going to suddenly