Smart Grid, Part 2: The Intersection of the Power and ICT Fields

Following on my previous post, today I focus on automated meter infrastructure (AMI) and field area network (FAN). Local area network (LAN) and wide area network (WAN) are well-known terms and do not need explanation. There are a few XANs to indicate the scope of the area covered. For example, a metro area network (MAN), usually citywide, is larger than a LAN but smaller than a WAN.

Smart grid introduced the term FAN. FAN is part of AMI, the infrastructure connecting the end consumer to the utility. A smart meter aggregates home power consumption data and passes them on to a FAN, which then transmits that data to a WAN, which delivers them to the utility.

For the average consumer, the smart meter is the gateway to the utility and the interface with the home area network (HAN). Although there are other gateways, such as broadband cable, DSL, and fiber modems and connectors, the smart meter is gaining a foothold as a gateway. Since the utility installs it, the smart meter is already compatible with the utility’s communications protocols. For that reason, it is becoming the de facto gateway.

The meter technology is unique, and I am not sure whether typical ICT vendors can enter the field easily. Some vendors, like GE, stand out among the who’s who in providing meters. In my PG&E territory, we had an analog (dumb) meter from GE before, and our new smart meter is also from GE. A big difference between dumb and smart meters, aside from analog vs. digital, is the communications capability of the smart meter. The smart meter has at least three functions: it aggregates/stores the power usage information (hourly or more frequently), transmits the aggregated data to the utility via the FAN, and receives the signal from the utility to control devices and appliances on the HAN.

A dumb meter stores the power usage information by advancing hands in the analog indicators, and it needs no specific internal memory. On the other hand, a smart meter requires some kind of internal memory to record the usage according to the frequency of measurement. In addition, a smart meter needs a mechanism to transmit and receive data and signals. A transmission chip or firmware is embedded into the meter logic for that. ZigBee (mesh wireless technology) is becoming the de facto standard for smart meters. (ZigBee is not a company but a consortium that dictates the ZigBee specification. A company that wants to implement ZigBee pays a license fee and implements its own version according to the specification. NIST is very cautious about declaring a technology a standard. For example, NIST has designated IP as a communications protocol but no others yet. ZigBee, Wi-Fi, and WiMax are under consideration to become part of the standard. ZigBee has started working on supporting IP but doesn’t do so completely yet.

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Data collected from each household are aggregated to a network access point (NAP) in the neighborhood. I have been looking for this point but have not found it yet. Since ZigBee does not support IP 100%, the communication between each smart meter and the NAP is via ZigBee.

Some information about PG&E’s smart meter can be found here.

Each NAP is now connected via wireless WAN. PG&E uses ZigBee for FAN, but other technologies could be wired  or wireless (WiMax) and BPL.

Zen Kishimoto

About Zen Kishimoto

Seasoned research and technology executive with various functional expertise, including roles in analyst, writer, CTO, VP Engineering, general management, sales, and marketing in diverse high-tech and cleantech industry segments, including software, mobile embedded systems, Web technologies, and networking. Current focus and expertise are in the area of the IT application to energy, such as smart grid, green IT, building/data center energy efficiency, and cloud computing.

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