Smart Grid Investment Nets Flexible Outcome for Hoosier Co-op
By Donald Book, CEO and General Manager — Dubois Electric
Tucked in the southwest corner of Indiana, Dubois Rural Electric Cooperative services more than 13,000 accounts in Crawford and Dubois Counties, as well as parts of Pike, Perry, Orange and Martin Counties. The service territory of more than 1,000 square miles is about an hour and a half in any direction from major population centers but it does serve an average of eight customers per mile of its total 1,622 miles of line, among the upper reaches for a rural co-op.
Dubois members had been self-reading analog meters since the co-op was formed in 1939. There were obvious drawbacks to this type of service and with newer advanced meter infrastructure (AMI) technology available, the organization concluded at a 2008 strategic planning meeting that its current system had reached its limit. Members had also changed over the years and were more than ready for automated reading, as well as faster outage restoration.
Engineering staff began evaluating AMI options soon after, looking mainly at power line carrier (PLC) and wireless mesh fixed technologies.
A primary consideration in an AMI system is cost per endpoint but having the option to do distribution automation and metering on the same network, wanting “last gasp” messages in an outage management scheme, and the full lifecycle costs of installation and maintenance all around are also strong factors.
Another main consideration for Dubois had to do with geography. Unlike the northern third of the state, southern Indiana has wooded terrain with many changes in elevation. About half of Dubois’ territory is covered by forest, with about a third spilling into the 202,000 acre Hoosier National Forest. That, and the state’s famous limestone formations (35 of 50 state capitol buildings are built with Indiana limestone) pose challenges in a utility network design.
PLC systems were looking like the winning option early on for Dubois, as the co-op could leverage existing assets already in place and found wireless mesh daunting because of the large amount of network hardware necessary. PLC is cost effective, particularly for long distances in challenging terrain. In fact, Dubois had a verbal agreement with a PLC vendor until it came across information about the FlexNet™ communications system from Sensus.
The point/multi-point network topology broadcasting over a secure 900 MHz signal seemed to offer good value with less hardware than mesh, open compatibility with enterprise systems, multiple applications on a single network and future expansion capabilities. When compared to PLC, the tower-based licensed spectrum technology made more sense.
Despite its advantages, PLC networks have to push signals through transformers and other distribution devices so bandwidth (frequency) has to be kept fairly low, making it a self-limiting communications technology. The longer data transmit time from the lower throughput creates higher latency, limiting interface with Distribution Automation (DA) devices.
In the end, what mattered most to Dubois was getting accurate meter readings and knowing if the point/mutlipoint technology performed as advertised. Could they trust Sensus to give them the necessary support every step of the way? Those unanswered questions were a bit unnerving for management, as other players had been in Indiana and the co-op space much longer than Sensus.
Dubois searched for other co-ops that had adopted fixed licensed spectrum AMI and came across Sawnee EMC in Georgia, serving what had been mostly rural communities north of Atlanta until rapid population growth in the 1990’s caused it to become part of the region’s metropolitan sprawl. Reports from Sawnee were encouraging.
The point/multipoint topology requires fewer assets (receivers) compared to mesh. Because licensed devices can transmit more power, they have a significant advantage on the signal part of this equation, sometimes up to hundreds of updates per hour in the case of a central collector. This is a significant advantage for DA applications. The noise in licensed bands is close to nonexistent, which makes the reliable range of licensed band for smart grid devices significantly better.
Dubois announced the decision to implement the Sensus FlexNet wireless network and iCon® digital meters at its annual meeting in fall 2010. Articles were written for the member newsletter to explain why the current meter system had to be replaced and how the new system would work. Letters were mailed to members in specific areas before any of the 29-member technical staff came on premises to switch out meters that included factual information on “smart” meters to ease any concerns.
It was also a good time to have members enrolled in online bill payment to further automate the billing process. Feedback was important to Dubois and so correspondence included a member survey, asking what future services and programs (such as demand management) they felt would be useful. Member response has been solid, offering valuable information for use down the road.
Physical installation of the network infrastructure and meters has been fairly straightforward since the project began around December 2010. There were some growing pains during the first month or two as staff became comfortable working with the handheld provisioning equipment. Installation since then has been smooth and is on target for completion in summer 2012. Residential applications comprise the bulk of installations However, the system is communicating with meters at several hundred commercial and industrial sites with a small mix of Elster meters. The hilly, limestone terrain in the Dubois territory is not suitable for farming, but the area is home to a thriving poultry industry where reliability is key.
Meters are programmed and provisioned at each premises. A photograph of the old analog meter is taken before the switch-out to avoid any billing disputes. Barcodes on the new meter are scanned into the handheld provisioning tool, longitude and latitude are automatically input into the meter and it’s then tested for signal continuity. Each installer can do about 35 per day and there will eventually be 13,000 intelligent endpoints deployed.
Dubois installed a server to manage the network and data at its central office in Jasper, Indiana. Six monopole antennae and six network base stations provide signal coverage for the entire service area. Only two towers had to be built; one at substation and one that the local fire department allowed to be constructed on its property. A contractor installed the antenna and ran co-axial cable, a very simple process. Dubois linemen were able to quickly install the FlexNet radio base station equipment. The first digital meter installed after the network was up and running was read in only five minutes.
Industry standards smooth integration
The benefit of having two-way communication between the new digital meters and central office enterprise system was immediate. The AMI system has an industry standard MultiSpeak interface to a NISC customer information system. Meter data is true and accurate, leading to few billing complaints. This capability has shown its value in billing on the many cabins and rental properties located in and around the national forest that don’t have year-round residents. Labor costs and bill collection headaches are reduced because Dubois can turn service on and off to these remote areas without truck rolls.
A truly impressive function of the AMI is the speed at which events are reported, usually in a minute or less. This makes a big difference in power restoration as the AMI is also feeding data to the NISC outage management system with outage notifications.
There was one instance in spring 2012 when a transmission line feeding a substation with more than 600 customers tripped. It was only off for five minutes and, during that short span, the OMS received 338 out-of-service calls from the meters. Of course, they called back in when the power came back on, but it was confidence-inspiring to see how fast the calls came in to alert Dubois staff that a substation was off.
Future expansion possibilities
The AMI system at Dubois has continued improving over time as customer billing data is fully-integrated and it has had several billing cycles under its belt. Of 10,500 meters installed in just over a year, only about a half dozen meters proved difficult to read. This error rate is reasonably acceptable and there are measures planned to make the system even better. What’s certainly true is that maintaining only six antennae is far simpler than the 100 plus receivers a mesh system would have required.
Dubois expects to have a GIS (Geospatial Information System) system in place by the last quarter of 2012 for digital representation of assets on a map. A decision was made to hold off on purchasing GIS and mapping systems until all the meters were installed but GPS coordinates are input during each replacement. DA applications will be in place when the company is ready to consider remote sensors compatible with the wireless infrastructure. Plans also call for demand side programs to manage peak loads, starting with an automated signal directly from the towers to a sensor on customers’ water heaters.
Beyond integration with various enterprise systems, the AMI will also be helpful in direct customer engagement. Once the OMS is fully vetted for reliability, there are plans for pushing outage notifications to affected customers via automated text messaging. Prepaid service is on the horizon as well to provide even more value to rental and vacation property owners.
Most important to Dubois is having a very positive customer response since the new system’s implementation. Other than an elongated billing cycle that raised some bills during the transition, there have been few complaints. Most customers are happy that they don’t have to read their own meters each month and that they have power restored before they can even pick up the phone to report outages. Although PLC systems are a popular choice for many co-ops, wireless proved to be a cost-effective technology for Dubois and is as rock solid as Indiana sandstone.