ARTICLE
Stillwater, Oklahoma, is a college town with spirit, culture, and youthful energy. It is home to Oklahoma State University and 50,000 residents.
The City of Stillwater is proud to provide electric, water, wastewater collection, and trash/recycling collection to more than 25,000 utility customers, which includes residents, businesses, and industry.
As part of the City of Stillwater, Stillwater Electric Utility (SEU) is the second largest municipal electric utility in our state, as well as the largest transmission owner and electric generator, overseeing and operating a total of 64 million watts of generation capacity. The electric distribution system spans 400 miles of overhead lines, 324 miles of underground lines and includes 8,585 distribution transformers, 12,238 poles, 3,791 streetlights, and other related electrical equipment.
In order to seek out solutions to improve service for our customers and increase efficiency, we conducted several pilot projects to test how improving our communications infrastructure could lead to better operation visibility and expansion for future applications.
Pilot 1: Improve Network Bandwidth to Connect Field Assets
With this type of municipal infrastructure, city systems are of critical importance to the city of Stillwater.
Learning about the successes of using outdoor wireless mesh solutions in Oklahoma City, Ponca City and other municipalities, our leadership team quickly recognized the importance of the network as the foundation for many other near-term and future goals. The city of Stillwater IT department originally began looking at ABB’s Tropos Mesh Network wireless solution as a possible alternative to low bandwidth VHF and 2G/3G cellular solutions for public safety vehicles and other mobile users, as well as a way to build an infrastructure to connect various field assets.
In 2009, we initiated a pilot network consisting of 20 fixed routers and two mobile nodes that were deployed in the downtown area near City Hall. The network had three gateways on buildings with connectivity to City Hall and was used for mobility testing and trial connectivity of key traffic signals in the area. It was successful but limited in scope.
Pilot 2: Improve AMR Collector Connectivity and Expand to Traffic Management
In 2010, with the availability of American Recovery and Reinvestment Act (ARRA) and Oklahoma Department of Environmental Quality grant funding, the city was able to implement an Automated Meter Reading (AMR) system for water meters. Given the communications network performance demonstrated in the initial pilot project and the broad service area as well as limited backhaul availability, an ABB wireless mesh solution was selected to provide redundant connectivity to the AMR collectors.
In addition, we installed routers from the AMR network deployment on traffic signal arms expanding the utilization of the mesh network for remote management and monitoring of a new traffic pre-emption solution.
The high-bandwidth connectivity to traffic cabinets made the implementation of a unified Intelligent Traffic Management System (ITMS) possible in 2014. This solution expanded to include a number of traffic cameras and connection and management of school zone warning lights. During this project, the point-to-multipoint (PTMP) radios were upgraded to provide additional backhaul capacity for the cameras and other applications.
In 2016 and 2017, the SEU constructed a dual ring fiber optic network (approximately 50 miles of single mode fiber) to interconnect all substations and key electric facilities. The fiber was routed near other city facilities, as well as several of our ABB mesh radios.
Distribution Automation
We had great success using the mesh communications network for existing applications and the opportunities provided by the new fiber network. So, when the SEU began looking at ways to expand and improve its 900Mhz SCADA radio system and building a Distribution Automation (DA) infrastructure, utilizing the private mesh network was a pretty simple choice.
Like most municipalities, we desire to have greater awareness and control of our DA capabilities to locate and isolate faults with reclosers correct our power factor with network connected controls, and have greater system awareness by collecting event and metering data.
Approach
We completed the installation phase of our network improvement project, adding approximately 30 gateways throughout our service area that are directly connected to our fiber optic backbone. We are now conducting a small pilot project - testing the DA system, including the installation of 16 nodes installed at capacitor banks and re-closers and connecting those assets to the wireless mesh network. The next phase of the project will include connecting more electric utility assets to the wireless mesh network for DA monitoring and control.
The last phase will be to enhance the wireless mesh network for a mobile workforce. We plan to add more nodes and possibly a few more gateways in locations where the network coverage is sparse. A denser network throughout our service area will allow field workers with mobile routers in their vehicles to remain connected to our network and the information systems they need to do their jobs quickly and safely while serving our customers.
Conclusions
The expected benefits are fewer service interruptions, as well as lower energy rates. Our ability to selectively isolate faults, and automatically restore power to un-faulted line segments will result in fewer customers affected, and for shorter durations. Also, since we are penalized for a poor system power factor, we can more efficiently dispatch our power factor correction capacitors with networked controls. This avoids a penalty from our electric wholesaler and allows our system to operate with lower losses.
We currently have close to 160 mesh radios spread around our city (approx. 34-36 square miles). While this has helped us achieve many goals with our service area and terrain, coverage is still sparse and presents challenges for workforce mobility. However, as we add more nodes for DA, it should help fill in the network and improve coverage for our mobile workforce.
Ultimately, City of Stillwater leadership envisions a high-availability communications network, comprised of both wired and wireless components, that allows our modern workforce the ability to have real-time awareness of our system, greater control of assets, shorter response times, and ultimately provide the best product we can for our customers.
We have experienced the benefits of wireless mesh technology at every step and will continue to enhance and expand capabilities, especially as they pertain to DA and mobile workforce management. Stay tuned for Phase II.
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About the author: Brad Stewart is IT Director, City of Stillwater, Oklahoma
