By Ryan Hentges, Minnesota Valley Electric Cooperative
Minnesota Valley Electric Cooperative (MVEC) is a small electric utility, so we take risks carefully but face the same communications issues as utilities with greater resources. In spring 2008, we faced three main challenges: how to link widely dispersed assets, expand automatic meter reading (AMR) and smart grid technology and maintain or increase data reliability. Like many utilities, we used various communications methods to manage backhaul, and we had definite ideas on which would best take us into the smart grid future.
AMR—Our Smart Grid Baby Steps
Our entrance into smart grid began in 2001 with the deployment of an AMR system to about 15 percent of our system. With 40,000 meters across a rural and suburban service territory, we needed to reduce labor and transportation costs to read our most rural locations. Our AMR systems communicated over modems, local wireless Internet service provider and DSL. Getting reads from our meters once a month was acceptable. During the years, what was acceptable changed as the requirements of smart grid technologies began to change.
Increasingly, we needed advanced metering infrastructure (AMI) and consistent, hourly kilowatt-hour readings, outage information, voltage information and blinks. Our supervisory control and data acquisition (SCADA) use grew from simple monitoring to substation control. We began to envision someday expanding outside the substation fence to downstream devices.
The more we explored smart grid technologies, the more we realized how integral communications are. If we couldn’t reliably communicate with our meters, we couldn’t reliably gather hourly data to present to our members. If we couldn’t reliably communicate to SCADA devices, we couldn’t reliably control them during outages. We realized our smart grid was only as smart as the weakest link, and that weakest link was communications.
The move to smarter technologies, we saw, only increased the urgency of the issue. As our reliance on technologies increased, we realized we had a communication problem, and we needed a better solution.
The Kernel of an Idea
One of our wholesale power providers, Great River Energy (GRE), entered an agreement with Arcadian Networks in 2007 to establish 700-MHz wireless coverage across GRE’s service territory. The network brought Internet protocol (IP) connectivity at broadband speeds to some of the most rural parts of MVEC’s service territory. The driving purpose for 700-MHz implementation was for GRE to consolidate communications to substations and other devices across a geographically dispersed territory.
GRE and many of its distribution cooperatives use the Arcadian Networks solution to communicate to more than 550 substations. The technology enables communications with multiple AMI systems accounting for more than 200,000 meters. In addition, more than 20 on-site generators are monitored using the network. Although GRE’s business case for the implementation did not include the value of distribution cooperatives’ smart grid technologies, GRE planed the architecture in a way that enabled member distribution cooperatives to take advantage of the wireless technology. In spring 2008, we began using the 700-MHz network for substations communications. Our experience has been excellent.
The first substations we moved to the 700-MHz communications previously had communicated via modems. These two substations were outside the reach of any type of broadband solution. The improvements achieved from moving to the Arcadian solution were immediate and substantial. We were able to get reads consistently from the AMI system and stopped driving 45 minutes one way to reset the modem at the substation.
After the success of the first two substations, we migrated additional substations to the 700-MHz solution. With promising data demonstrating a solution to the reliability issue and increased savings and smart grid readiness, we extended use of Arcadian Networks throughout 2009, eventually relying on it at more than half of our substations.
Dramatic Before and After
Again, the benefits were clear and immediate, especially at one substation. Figure 2 (page 40) is a graph of communications to one of our substations. We had particular troubles with this substation that was communicating over a local wireless provider’s solution. The graph represents pings every five minutes to the substation communication device. July through November saw significant downtimes and communication issues. At the end of November, we transitioned to the 700-MHz solution. After that, communications were stable.
In addition to the measurements in Figure 2, we found these factors compelling reasons to rely on an enterprisewide 700-MHz solution. It is:
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1. A single communication technology. Because the 700-MHz solution is available to all substations and field devices, we have fewer communication technologies to support.
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2. Economically competitive. The cost of investing in the 700-MHz solution compares favorably to that of other communication technologies.
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3. Secure. The private broadband solution provides an exclusive, safe platform.
- 4. Responsive. Support issues have been addressed quickly and completely.
Today, we build our entire network on the Arcadian Networks’ 700-MHz platform to communicate at all 22 of MVEC’s substations, a distribution automation device and a wind-generator meter. We anticipate high scalability and interoperability because the solution can incorporate virtually any technology, including:
- Arcadian 700 MHz
- WiMAX (802.16e, 802.16d)
- Wi-Fi (802.11b/g/n)
- 3G/4G (EVDO,GPRS,EDGE,HSPA,LTE)
- Serial, USB, Ethernet
- 900 MHz (ISM and MAS) industrial radio
As we continue to deploy and use smart grid technologies, we continue to monitor the performance of the system. The following are key measurement areas we use to monitor the success of the network:
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1. Stability. We currently achieve 99.7 percent uptime on our devices communicating on the Arcadian Networks’ network. This measurement is end-to-end and includes non-Arcadian Networks devices.
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2. Performance. We currently experience 172 millisecond average response time. Like the stability measurement, this measurement is end-to-end.
- 3. Capacity. Our experience has shown that technologies such as AMI and SCADA can operate over the network without creating capacity issues.
A smart grid is only as smart as its weakest link. With the rural substation communications issue essentially solved, we see the wireless network as key to unlocking their smart grid future. After two years of testing every step, we’ve embraced 700 MHz for AMR, or fixing problem substations, and as the key to smart grid communications across our enterprise. Our thoughtful and staged rollout served our needs to carefully manage our small utility’s resources. In the process, we’ve compiled extensive records demonstrating the value of private broadband networking for smart grid communications for any utility.
