According to Tom Ayers, president and CEO of Tropos Networks, smart-grid communications infrastructures are being architected as a “network of networks,” comprised of multiple technologies.
“For the distribution area, the technologies include wireless mesh, point-to-point, point-to-multipoint, and in some remote locations, cellular,” he says. “The precise mix will vary based on the planned applications and their requirements as well as the composition of the service territory (mix of urban, suburban and rural).”
Distribution automation (DA) applications are proving to provide significant benefits to utilities (the natural leaders in smart-grid buildouts) by increasing power quality and reliability, and they can be deployed without having to impact customers directly. Ayers believes wireless is the most cost-effective way to scale to deliver connectivity to millions of distribution endpoint devices (capacitor banks, transformers, switches, etc.). Any network for high-impact DA applications requires low latency (sub-20 millisecond) and high reliability (99.999 percent) characteristics, as well as providing visibility and management for communications to millions of devices across hundreds of square miles.
According to Tropos, private networks will continue to dominate as the network of choice for smart grids. The most common reasons for preferring private networks are:
>>Reliability. By owning and controlling the network, utilities can select the level of reliability desired for each application. Utilities can achieve predictable performance levels and assign a priority level for each application without worrying about competing with public traffic from millions of cellphones, especially during the chaos of any local emergency.
>>Security. Security for utility communications needs to include support for industry security standards for securing data. Where private networks have a significant edge over public networks for security are in terms of reliability, survivability and control.
Mesh networks will continue to be a smart architectural choice for the smart grid. There are different types of mesh network technologies commonly seen in smart grid deployments including 900 MHz meshes popular for metering LANs as well as high performance mesh used for distribution area network (DAN) communications.
Cost of ownership for private networks is substantially less. Tropos estimates that the breakeven for public vs. private networks is a little less than four years where AMI backhaul is the first application deployed. As such additional applications as distribution automation are added, the breakeven point is reduced.
“As utilities move into deploying smart grids, building an end-to-end network for each application simply doesn’t make sense,” Ayers notes. “By owning the network rather than leasing, utilities have end-to-end visibility into network performance as well as control over coverage and capacity.”