Green Mountain Power plans for grid automation.
Active in the electric utility industry for years, grid automation is viewed as one of several core technologies needed to update the industry's electric infrastructure and transition it to a smarter grid. Vermont Transco LLC and all of Vermont's electric distribution utilities took a unique approach to grid automation by coordinating a statewide application to secure a smart grid investment grant from the American Recovery and Reinvestment Act.
As a result, the U.S. Department of Energy (DOE) awarded the utilities a US$69 million grant, and each utility, including Green Mountain Power (GMP), is involved in projects that will procure and deploy smart grid technologies between April 2010 and April 2013. As an example, along with substation and distribution automation, GMP is deploying advanced metering infrastructure (AMI) and upgrading its customer information systems.
To springboard this initiative, GMP — Vermont's second-largest investor-owned utility, which serves 95,500 electric customers — is leveraging a statewide “Light the Fiber” initiative that will interconnect a fiber-optic backbone to approximately 65 substations in the GMP territory. The core objective of GMP's smart grid program includes improving system reliability and gathering data that can be turned into actionable information. GMP's long-term vision includes the ability to integrate renewable and distributed energy opportunities, reduce carbon-dioxide emissions, improve system efficiency and enhance its customer partnerships to ensure efficient use of energy.
Immediately after receiving funding, GMP sought an experienced smart grid/AMI associate to provide consulting, facilitation and project management services related to the scoping, planning and execution of its smart grid initiatives. GMP selected Science Applications International Corp. (SAIC) for its deep domain expertise with smart grid infrastructure programs and proven program management practices.
Part of the upfront planning included a detailed interoperability review of interfacing legacy and new substation automation equipment. This included an examination of existing infrastructure and new hardware and software products to generate an evaluation of both technology and cost information to enable GMP to meet its grid automation goals.
SAIC then evaluated several alternatives, ranging from expanding legacy supervisory control and data acquisition (SCADA) capabilities to a hybrid solution of old and new technology implementations to an exclusively new technology solution. SAIC also evaluated substation automation standards (DNP3 and IEC 61850).
Finally, the company prepared a detailed implementation plan to enable GMP to meets its commitments to the DOE regarding schedule and to take full advantage of the funding. The implementation plan provides checkpoints along GMP's technology road map to fully leverage lessons learned and provide continuity with engineering and construction resources.
Substation Automation Project
Key to GMP's substation automation project is its strategy for a telecommunications network. GMP employs a variety of telecommunications media between its control centers and substations to support protective relaying applications, SCADA and voice communications. Existing telecommunications to GMP's substations are largely radio and leased wire lines from the local telephone company. Limited-leased fiber-optic lines are in use today.
During the course of its substation automation project, GMP looks to leverage fiber-optic lines as its exclusive communication medium between control centers and substations. This technology choice affords significant benefits that include extremely large information-carrying capacity and immunity to electrical sources of interference and noise. The utility expects throughput improvements from 56 kbps with the existing infrastructure to 1 Gbps with the fiber-optic networks.
To take advantage of this improved telecommunications network infrastructure, GMP will retrofit its substation communication equipment with substation-hardened routers and Ethernet switches by implementing a solution to connect each substation's local area network to the fiber backbone.
These cyber-security appliances are developed specifically to establish an electronic security perimeter around critical cyber assets found in control and automation systems. These routers meet the North American Electric Reliability Corp. (NERC) critical infrastructure protection requirements needed to protect North America's bulk power system by preventing operations disruption through accidental or malicious acts. Key cyber-security features include a firewall, virtual private networking, data encryption and intrusion detection.
Further, GMP looks to replace electromechanical relays with new intelligent electronic devices (IED), install satellite clocks, upgrade legacy regulator and recloser controls, and install local human machine interfaces in its larger substations. In addition to providing greatly enhanced functionality, the removal of “dumb” devices and discrete analog transducers will enable GMP to reduce wiring and potential failure points significantly.
These equipment improvements will provide remote engineering access, giving GMP the ability to change protection settings, provide diagnostic information and offer event data details. These improvements also will add redundancy for control and status of breakers and reclosers. Collectively, hundreds of data values for a variety of power parameters will be available where limited information was accessible before.
Beyond the substation improvements, GMP will install improvements on its 34-kV subtransmission system, including additional motor-operated devices on critical air-break switches, directional fault indicators and associated IEDs, and dedicated fibers for line current differential protection. Leveraging distance to fault information available from the IEDs, in combination with bidirectional optical fault indicator information, will enhance fault locating.
Detection of faults by 34-kV breakers will eliminate operators having to guess which section is shorted and enable GMP to improve restoration times significantly. Without this information, operators would have to isolate sections remotely and shoot the line (meaning to energize the line remotely without having previously patrolled the line or corrected a line for a faulted condition) to determine if the faulted section was located, largely by trial and error. Through improved information, automation will determine the exact fault location easily and quickly, and work to restore power efficiently.
Today, GMP has limited midpoint reclosers with SCADA capability. The distribution automation project will extend SCADA capabilities to existing field devices, and part of the project will be to install new reclosers and motorize midpoint sectionalizing equipment. For its distribution automation telecom strategy, GMP will migrate from a radio telecom network to a public cellular network. Extreme terrain in GMP's service territory is a limiting factor for radio communications. Additional improvements include upgraded recloser and capacitor controls, wireless 12-kV fault indicators and automatic feeder restoration capability.
Identification of a 12-kV fault, with a fault-indicator-equipped circuit with motorized sectionalizing equipment, will automatically sectionalize the faulted section of the circuit. Through combining distance-to-fault information with wireless fault-locating equipment, GMP will make a significant, timely leap in restoring service during unplanned outages.
Beyond expanding the installation of distribution automation to additional field devices, GMP is evaluating future projects on its technology road map that align with the core objectives of its smart grid program.
As part of these next steps, GMP will explore the installation of a distribution management system. This decision support tool will extend GMP's existing SCADA solution to assist the control room and field personnel with the monitoring and control of the electric system. The utility anticipates advanced applications will include further leveraging of AMI data, online power-flow tools, intelligent alarm processing, switching order management, volt/volt-ampere-reactive optimization, contingency analysis, adaptive protection, fault location isolation and management of distributed energy resources.
GMP is dedicated to achieving grid automation and providing tangible benefits to its customers and employees. The implementation of substation and distribution automation projects across the nation will improve an aging electric infrastructure. GMP's move to a smart grid includes plans to update its electric infrastructure, integrate information systems and improve telecommunication systems to deal with the increasing volume of data and complexity.
GMP is seeking reliability improvements expected through enhanced SCADA connectivity, device management, fault analysis and system protection tuning. Through secure and high-bandwidth connectivity, GMP will have engineering access to field devices that will improve system models used to achieve operational efficiencies and energy-loss reductions. Further, improved device management will enable GMP to improve phase balancing, implement volt/VAR strategies and optimally integrate small renewables.
Ken Couture (firstname.lastname@example.org) is Green Mountain Power's engineering manager. With more than 20 years of experience in the utility industry, Couture is involved with operations and construction management, and oversees the transmission, distribution and substation engineering as well as GMP's grid automation rollout.
Keith Kerzel (email@example.com) is vice president of smart grid infrastructure for SAIC Energy, Environment & Infrastructure, LLC, a wholly owned subsidiary of Science Applications International Corp. He offers 24 years of energy and utility industry expertise to customers across the country. Kerzel is a professional engineer and a project management professional.
Green Mountain Power
Science Applications International Corp.