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AMI: Smart Enough?

Metering potential and limitations for smart-grid design.

Fortnightly Magazine - June 2009

they can be installed at selected points on MV feeders, and connect to a utility’s standard meter system, communication system or data management system.

Feeder meters can offer additional benefits, one of which is enhancing diversion detection. A utility may create a comprehensive diversion detection solution by combining data from premise meters and feeder meters. Sophisticated data processing of the measurement of power flow into, and out of, a feeder segment bounded by feeder meters, and premise-metered consumption from premises attached to the same segment, can provide diversion detection, diversion amount, and total segment technical losses. By localizing to a segment, diversion investigations can be greatly accelerated. Voltage-drop analysis at the premise meters may further localize the diversion.

Another benefit of feeder meters is as a tool to assist fault detection and location. Smart line sensors can be used to detect, classify, and locate faults, but they are expensive, and not every utility will want to deploy them in large quantities or provide a high–performance communication network for them. Although feeder meters won’t capture information as fast as line sensors or operate at the same high speed (sub-second) rates necessary for grid protection and control functions, they can be used to perform some of the functions of line sensors, such as support for outage management, dispatch, and field service.

Feeder meters also can be used to help in the management of the grid in the presence of distributed generation (DG). DG and storage encompass emerging technologies that allow placement of energy sources at various points on a grid, including at customer premises. The presence of technologies will change distribution grid power flows in ways the grid was not designed to handle. Significant penetration of DG into a power grid introduces new complexities in grid-power flow, volt/VAR regulation, and optimization and power-quality control. As penetration of these technologies on a distribution grid increases, eventually a tipping point is reached where it becomes necessary to apply smart-grid technology to help restore manageability of the distribution grid, primarily by improving observability of the grid. Meters also may be employed at the point of common coupling for distributed generation to provide visibility on DG power flows and impact on power quality.

Rethinking Metering

How far can smart metering take utilities toward the realization of a smart grid? The answer depends on what meters and sensors a utility decides to implement and the degree of intelligence desired. But the options with meters and sensors already possible can be quite sophisticated. The emergence of new meters, sensors, and other technologies is creating opportunities now to rethink traditional approaches to commercial and residential meters and consider more powerful ways to plan for adding smart grid capability—for today and tomorrow—in the continuing journey to high performance.