How Advanced Metering Can Contribute to Distribution Automation
Written by David G. Hart
Traditional distribution automation typically consists of feeder devices such as reclosers, switches, fault current indicators and capacitor banks, which improve reliability and network performance. However, a major obstacle to realizing many automated functions is the lack of a ubiquitous communications network across the distribution grid. To overcome this barrier, utilities are eying the synergistic benefits advanced metering can bring.
With the deployment of advanced metering infrastructure (AMI), utilities are able to collect information from consumers in shorter time intervals, in response to utility and/or consumer needs. This allows for consumer education and better awareness of household energy usage, leading to a wide array of benefits not possible with traditional one-way technologies: among them increased energy conservation; remote meter reads and service connects/disconnects for customers moving in or out of residences; and outage detection.
In addition, AMI deployment creates a system-wide communications network to every service point on the utility grid. This communications infrastructure will link TCP/IP, IEC 61850 or DNP (distributed network protocol) devices across the grid via battery backed-up access points for continuous service, as well as enable IEEE 802.15.4g connectivity on the AMI mesh to monitoring and control points.
With these features of AMI, utilities are able to realize the new functionalities available when combining the system with the traditional distribution automation (DA) infrastructure.
DA-AMI convergence is providing unprecedented opportunities for power grid modernization that have not been fully explored previously, including transformer and feeder monitoring, outage management, cost-effective fault isolation and electric vehicle integration. One application that has obtained significant results from a DA-AMI infrastructure is voltage conservation (VC).
Voltage conservation, also known as conservation voltage reduction, decreases the amount of electricity needed to service a given area without causing detrimental changes in power quality or reduced supply to customers. With a goal of cutting energy losses and consumption by operating at the lower end of approved voltage ranges, voltage conservation is a beneficial way to access energy and revenue savings while increasing customer satisfaction with no additional effort on the customer's part.
Historically, VC has relied on measurements at substations and has used simplified models to predict the voltage at the customer service point, resulting in a very conservative approach. AMI systems enable a more aggressive approach by making voltage information available from smart meters along the distribution feeder and allowing for direct control of load tap changers and capacitor banks that are on the communications network via basic Internet protocols.
While installation of meters and ancillary equipment constitutes the primary investment of implementing a DA-AMI convergence system, payback from grid modernization applications, such as voltage conservation and reduced energy consumption, more than compensates for these initial costs. In addition to minimizing damage to distribution equipment caused by potential voltage overloads along the grid, various other qualitative and societal benefits of voltage conservation include deferred construction of new generation, reduced greenhouse gas emissions and decreased dependence on fossil fuels.
Currently, the missing link to overall implementation of voltage conservation is an effective and pervasive communications system. Because of this, many utilities today have little or poor visibility outside of the distribution substation and down to the customer. AMI systems, such as Elster's trademarked EnergyAxis System, provide the necessary multi-technology communications infrastructure to fully implement a VC program.
Smart meters can monitor the service voltage on a continuous basis, thereby ensuring adequate visibility at various locations on feeders. AMI systems allow the utility to monitor key points frequently and harvest data in near real-time for detection of changes in voltage levels and assure that any voltage adjustments result in the desired effect.
AMI systems function as the "eyes" throughout the distribution infrastructure by providing information for the Distribution Management System (DMS)/Supervisory Control and Data Acquisition (SCADA). Once the information is processed, the AMI system also provides the communications infrastructure needed by the capacitor banks and load tap changers to implement actions, presenting an overall solution for voltage conservation.
Customers of utilities that employ VC use less energy and therefore have smaller household electricity bills, while their aggregate energy savings translate into lower power generation requirements and a decrease in greenhouse gas emissions. All aspects of the VC program fall within the utility core competence with a focus on grid operation and efficiency.
While VC is one of the first major applications to leverage the benefits of the DA-AMI convergence, it is only the beginning of what’s to come. For the first time, smart grid solutions provide system-wide observation capabilities across the distribution grid. The new information collected and processed will drive many more improvements to the grid operation and efficiency.
David G. Hart, a senior member of IEEE, is Senior Vice President, Systems & Products, at Elster Solutions LLC, in Raleigh, N.C. Elster is the world's largest metering and solutions company with over 3 million smart meters deployed. Hart earned his Ph.D. and M.S. in electrical engineering from Clemson University, in Clemson, S.C. In 1992, he joined what was then the ABB Transmission Technology Institute, where his most recent position involved distribution and feeder automation.