Transmission & distribution
First trial of the smart city concept1 November 2008
The USA will soon have its first fully functioning ‘smart grid city’, an Xcel Energy initiative designed to prove the concept of a managed, two-way interactive distribution system that can respond immediately and intelligently to fluctuations in load and supply as well as to spot changes in customer choice. The phased conversion of 50 000 residential and business customers is already underway.
In March 2008, Xcel Energy’s Smart Grid consortium announced its intention to build the USA’s first smart grid in the city of Boulder, Colorado. This project will be the country’s largest of its kind and will involve the densest concentration of smart grid technologies in a single community to date.
A smart grid uses emerging technology to fundamentally modernise the way energy is created, delivered and used. While the industry has various definitions of an ‘intelligent grid’ Xcel (and its consortium partners Accenture, Current Group, Schweitzer Engineering Laboratories, Ventyx, GridPoint, OSI Soft) believe that a smart grid must be built on a design for a fully interconnected system that allows customers to more actively participate in decisions about their own energy use. Additionally, there are digital technologies available now that will allow the utility to reliably produce and deliver that energy through real-time, automated controls. It is such a grid, or rather, a grid overlay, that is in the first phase of construction right now in Boulder, under the trademarked name SmartGridCity.
Again, definitions vary but it is generally agreed that a smart grid is a power system that combines traditional and cutting-edge technology to create a system that can support the increasing numbers of digital services desired by consumers, incorporate new energy sources/users including renewables and hybrid vehicles, while effectively managing the necessary flow of energy.
Boulder has been selected as the guinea-pig site because it is considered the right size for a project such as this, and offers a useful mix of residential and commercial customers. It is home to academic and research institutions (including Colorado University, National Centre for Atmospheric Research, and the National Institute for Standards and Technology) already working with this emerging technology and studying long-term benefits.
Such a grid offers the potential for:
• Adding more clean and green power sources in the fuel mix—greatly improving power delivery and reliability while optimising environmental benefits.
• More choice about when, how much and what kind of energy consumers use.
• A digitally enhanced, more resilient and stable grid that is less prone to outages and improves power reliability.
• More energy efficiency and conservation options for consumers.
With the help of customer surveys Xcel has also decided on a number of new services that can ultimately be offered, including on-line tools to track and alter energy use, energy management in response to real time or green energy price signals, advanced smart meters that communicate with domestic devices, source information to enable the selection of, for example, low-emission sources, and smart charging options for hybrid vehicles.
The first step in deploying SmartGridCity is the installation of the high-speed communication network and sensing equipment on the distribution network, which began in June. The consortium has completed the communications network design and installed nearly 15 000 Landis+Gyr meters. These smart meters will allow interval metering, two-way communication (or ‘pinging’) between the customer and the utility, and provide a detailed usage history and automated meter reading.
Also in phase I, which was scheduled to be finished by August, were included upgrades to two substations and five feeders, and the creation of a Web portal to provide consumers with insight into their energy use and information for better home energy management.
Phase II, to be put into action in September and finalised by December 2009, involves:
• Completing the installation of a distribution and communication network for remaining areas within Boulder (an additional two substations, 20 feeders and 35 000 premises).
• Expandeding the number of residential automation installations.
• Enabling Web portal access to customers.
• Deploying additional smart meters.
• Commencing the integration of plug-in hybrid electric vehicles, and solar and wind generation sources onto Boulder’s grid.
Beginning in 2009, the consortium also expects to begin an initial assessment of the technologies.
In order to create a true baseline for comparison of traditional and non-traditional (smart grid technology) services, a small segment of customers will be expected to keep their existing meters, although system-wide smart grid benefits will be available to all who receive service from upgraded distribution facilities. The primary means of communication across the new network will be broadband over power lines (BPL). Nearly 90 % of the city will be connected with BPL; however, Xcel Energy will also test wireless capabilities in parts of the network.
For the demonstration phase starting in 2009 the system will feature monitors, controls and automation for two substations and feeders connected at a tie switch.
This will create opportunities to enhance reliability—and avoid outages—by designing a self-adapting, self-correcting grid that can:
• Detect, isolate and restore load for permanent faults and failures.
• Identify source voltages losses (for example, transmission line outages, transformer lockouts) and restore voltage from an alternate source.
• Allow automated switching between feeders and automated routing between substations.
• Create faster recovery times and shortening durations of failures (for example,by eliminating the need to send a crew out when problems can be avoided completely or resolved remotely.)
• Allow operators to see current and load while offering control over smart devices to manage electricity demand.
• Improve maintenance by prescribing it on actual conditions and real-time environmental factors (rather than simply anticipating conditions.)
• Provide sequence-of-events recording and viewing for post-event analysis.
SmartGridCity will boast the largest and densest concentration of these emerging technologies to date.