More to Meters Than Meets the Eye
- October 19, 2012
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The unrelenting treadmill of Moore’s Law steadily makes electronic components more powerful even as it makes them smaller and more economical. This has revolutionized electronics, telecommunications and information technologies. It will do the same for smart meters that will be supplanted by advanced intelligent electronic devices (IEDs), just as telephones have. They will do much more than measure, record and report consumption and limited end-point data about the distribution system. Meters will become integral to grid intelligence and control in ways not yet fully recognized in smart grid discussions. While this will provide many benefits, it will also have implications that utilities should be preparing for.
The electromechanical meter has gradually morphed into an electronic counterpart that does essentially the same thing: measure, record and report energy consumption and power demand. The predominant application of smart metering has been measuring consumer energy consumption in smaller time increments for critical peak pricing and demand response, but many new applications will be desirable, even necessary. A mere electronic equivalent of the electromechanical meter is not only not the state of the art it will not be adequate for a truly smart grid. The smart meters being installed today will become obsolete in timeframes of months and years, rather than the decades of useful life provided in a different era by electro-mechanical meters. (Unless, of course, they are true IEDs whose functionality can be updated and upgraded just like the operating systems and apps on smart phones.)
Let’s review some capabilities that today’s smart meters provide to utilities beyond time-of-use consumption data. They provide several meter-to-cash advantages. They are more accurate. Electro-mechanical meters slow with age and thus don’t accurately record actual kilowatt hours consumed. (This effect becomes even worse if the consumer’s power factor varies much from unity. Thus the complaint that a customer’s bill jumped after a smart meter was installed; the surprise is that they moved to accurate bills.) Smart meters equipped with remote connect/disconnect capabilities can cut time and eliminate truck rolls for routine matters such as a residence becoming vacant or changing hands or non-payment of a bill. Some smart meters record changes in their physical environment, signaling possible tampering or in some well-publicized cases, overheating.
Most smart meters can tell the utility whether they’re on or off, helping pinpoint outages more quickly and confirming when restoration has occurred. The pattern of meters reporting power off can enable more accurate and quicker utility analysis of the cause and extent of a service outage and speed restoration of service. That information in turn helps the utility keep customers informed on the cause and duration of an outage so customers can cope. That’s a major improvement over the past century of electric service.
Another grid-side advantage of smart meters that can measure and report voltage is enabling volt/VAR optimization and conservation voltage control. Prior to smart meters, a utility had to estimate voltage and current for a line based on a computer model of the line. The challenge was to ensure that the voltage was never too low anywhere on the line. That usually meant maintaining as high a voltage as allowable (sometimes more) for most of the customers most of the time. Volt/VAR control depended on macro devices such as a tap changer or voltage regulator at a fixed location that operated based on the voltage at that device. But the lowest voltage on a distribution line is at the point that’s electrically the farthest away from the power source, and the highest is electrically closest to the source. This varies as a function of time and location based on customer demand, system configuration and operating conditions. Some smart meters can provide accurate voltage readings at many points along the line that can enable the utility to better control voltage. This in turn can reduce power demand, distribution line losses and consumer energy consumption as well as improve power quality and extend equipment life for the utility and its consumers.
So some of today’s smart meters can enable a utility to better monitor and control their grid, because the meters are telling the utility things that they didn’t used to know. Most fully electronic smart meters are continuously measuring voltage, current and phase angle and so are the equivalent of a SCADA monitoring point. Unfortunately, not all smart meters can make this data readily available to the utility in real time.
Some smart meters can sense and report other data like meter base temperature. In a case I’m aware of at a cooperative utility in Texas, that sensing capability resulted in the utility dispatcher getting an alarm for an abnormally high temperature at a meter. A field crew was dispatched and found a problem with the meter base that would likely have resulted in a fire. Think about it. Should a so-called “smart” meter catch fire without the capability to report it to the utility? Should a consumer have to let the utility know that their smart meter is on fire?
State of the art smart meters (i.e., IEDs) are going to have, in addition to their sensing capabilities, analysis and control capabilities because the addition of these digitally based capabilities is inexpensive and the added functionality will be useful, even necessary. After all, the very nature of the electric distribution system is changing rapidly with the advent of distributed generation and control, PHEVs and EVs, automated demand-side energy management systems. The grid is moving toward decentralization, and so grid monitoring and control must do so as well.
In California, SolarCity is putting solar photovoltaic (PV) generation on people’s roofs via a 20-year managed services agreement. A utility must know where and how such an installation affects system operations. Their distribution system was not originally planned and constructed to maintain reliability, safety and power quality in the presence of distributed generation and storage. If the PV systems are designed correctly, when a line goes dead the inverter stops inverting DC to AC and delivering power onto the line. The utility need to know for certain when it sends out a crew to work the line that it’s no longer carrying power – people’s lives are at stake. IEDs distributed throughout the distribution network will provide that assurance.
If two or more plug-in hybrid electric vehicles (PHEV) are charging simultaneously at a residence, that “clustering” could overburden an upstream transformer that wasn’t designed for so high a load (and depress line voltage in the vicinity). Programmable IEDs that can accept a number of inputs and issue a number of outputs, including on/off could cycle the PHEV charging in a way that avoids overburdening the transformer.
We simply don’t know yet everything that utilities and their consumers (and disintermediaries) will want or need to do in an intelligent grid. Until smart meters are supplanted by IEDs that can accommodate over-the-air software upgrades, the current generation of smart meters may limit the options. Complete smart meter deployments could have to be replaced in timeframes that may surprise and possibly dismay many stakeholders, including regulators and customers. Stay tuned as we blog further about the fact that there is so much more to smart meters than you are thinking now.
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Image: Smart Meter via Shutterstock