Ultimate guide to AMI: 22 questions to ask BEFORE you buy a smart meter



Editor's note: Smart Grid News is working with experts from Elster and other leading smart grid companies to create the ultimate guide to AMI -- a full-scale, start-to-finish, everything-including-the kitchen-sink compendium of best practices, lessons learned, and future directions. When it's complete, we will make it available to you as an eBook. In the meantime we're publishing select excerpts. In this installment, Jeff Richardson of Elster explains that buying an AMI system is very complex and has dozens if not hundreds of considerations. The physical meter itself is one part of the equation. Below Jeff highlights 22 questions about the meter itself that you will want to include as part of your overall assessment before you buy. These are certainly not all of the questions you need to ask, but they are some you might not have considered. Scroll to the bottom to access additional installments in this series. -- Jesse Berst


By Jeff Richardson


The utility industry’s wholesale move to smart metering is a foregone conclusion. Choosing the right smart meter, however, isn’t quite as obvious.


Not all smart meters are created equal. So what exactly should you be looking for? You should ask 22 questions, which fall into the following six categories:


A.    Safety first

B.    Accuracy and reliability

C.    Dependable performance

D.    Extended life expectancy

E.    Minimal environmental impact

F.    Beyond traditional metering


A. Safety first


1. Can the service switch be left in an indeterminate state? Look for a meter with a service switch that cannot be left in an indeterminate state -- a system that identifies the status of the switch and a sensor that can report whether load-side voltage is present. If your customer is using a backup generator during a major power outage and the switch suddenly closes in to the independently energized circuit, the result will likely be irreparable physical damage.


2. Does it have a surface-mounted load break switch? Smart meters that come equipped with a surface-mounted button for operating the load break switch may, at first blush, seem like a great idea. It’s best, however, if your meters don’t have them. The reason? Meters are often located in hard-to-access places, and requiring your customers to interact with the meter is unnecessary and potentially unsafe.  It is one thing to ask a customer to check his breaker panel, but another thing altogether to ask the customer to operate utility-owned equipment. 


3. Does it have adjustable blades? Some meters incorporate blades that are capable of slightly adjusting their alignment. This is a useful, but not always standard feature that makes them better able to make a solid connection with a less-than-perfect socket. Meters that fail to make a strong connection could generate excess heat.


4. Does it have secure connections, especially current conductors? Secure connections are essential to safe operation over an extended period of time. Open the meters and compare the way in which its components are secured, especially the strength of the connections in the primary current path. Mechanical engineering of the meter is just as important as its electrical engineering.


B. Accuracy and reliability


5. What is the failure rate? Most smart meters have a failure rate of approximately 0.5%. Some - subject to a more rigorous verification strategy - have surpassed this, achieving a failure rate of 0.3% and, in some cases, as low as 0.2%.  Select one of these. Though the difference may seem small, the fewer failures the better.


6. Does it sample simultaneously throughout all three phases? Meters use different methods to sample power. When you choose a polyphase meter, look for one that samples simultaneously throughout all three phases, as errors can be introduced when power is sampled at different times.


7. Does it have precise resolution? Resolution also varies, from as low as 8 bits to as much as 21. Resolution is important to measurement precision. Measurement precision is the ability to very accurately measure over and over again - to achieve accuracy reliably.  With utility automation (especially self-healing), precision is vital to the ongoing health of the electric system. Precision is key to ensuring that your automation will perform as planned for many years to come.   


8. Does it have a supercapacitor? Some smart meters use batteries to keep time across a power outage. The use of a supercapacitor can either prolong battery life or reduce the need for a battery in a meter. This is important because of all the components that are commonly used in meters, batteries tend to be the most maintenance-intensive. Some smart meter designs don’t require a battery. Find out what your chosen meter uses and why.


9. Does it store data in the meter, not the comms module? The meter is still the cash register; don’t forget this paramount function.  Your meter shouldn’t sacrifice any measurement accuracy or precision for the sake of achieving convenience. Choose one that performs all functions and stores the data in the meter itself, not in the communications module. Meters that conduct these functions internally are not only more accurate, but also much easier to audit, as the meter is generally considered to be the ultimate authority in the case of a dispute or disagreement.


10. Does it identify and report anomalies? Unfortunately, anomalies sometimes occur in interval data, due to events such as power outages and clock adjustments. Choose a meter that is able to identify and report these anomalies so that the data can be correctly interpreted. Accuracy and billing verification will both be enhanced.


C. Dependable performance


11. Does it have an opaque cover? Opaque plastic covers or housings significantly reduce thermal gain and internal heating, improving accuracy and extending the life of the meter. Standard on most meters, this is an important design feature you don’t want to be without.


12. Does it exceed ANSI standards? While all meters used in the U.S. must meet the ANSI standard, only some exceed it. Look for a meter that’s been subjected to additional engineering and manufacturing tests designed to guarantee even greater accuracy and reliability. For example, manufacturers that perform thermal cycling on every meter board as part of their production process achieve higher reliability.


13. Does it avoid metal oxide varistors? Some meters use metal oxide varistors (MOV) to protect the electronics from high voltage surges. Look for a meter that does not use MOV across the power line. MOVs directly across the power line have been known to fail catastrophically, causing meter failure.


D. Extended life expectancy

14. What are the warranties and return rates? Meter failure rates tend to follow a "bathtub” curveâ€"that is, they’re highest immediately following deployment and as the end of their normal life expectancy approaches. Ask about a meter’s longevity, and for added assurance, check the manufacturer’s warranty and return rates.


15. What is the technology lifecycle and is firmware field upgradable? Choose a meter provider that won’t force obsolescence. Technology is changing rapidly; you want a meter that can be readily and remotely modified or upgraded. Look for a vendor whose early smart meters are still in use today and whose newer firmware for metrology and communications is downloadable to current hardware.


16. How many openings does it have in the base (and how small are they)? Look for a meter that has fewer or smaller openings in the base. Openings can let in water or insects that may cause damage to the meter. This is especially important in higher voltage installations.


E. Minimal environmental impact


17. Does it snap together and does it have the recycling symbol? For minimal environmental impact, choose meters that snap together. They’re easier to disassemble and therefore easier to recycle or repurpose.  Look for the recycling symbol. Less desirable components can be separated and recycled or discarded, while other parts can be re-used.


18. Does it the manufacturer use sustainable manufacturing? By using common components across the product line, some meter manufacturers exhaust surplus materials from one product by employing them in another, different product. Besides reducing waste, this tactic eliminates the need to invest in additional designs and materials, thus diminishing the cost of production and the price of the meter. Ask vendors about their design and manufacturing practices.


19. How much energy does it use? Some manufacturers have also managed to decrease the amount of energy their meters need to function properly. Thus, they’ve also lowered the meter’s internal temperature (improving safety and reliability), reduced parasitic load (lowering operating costs) and helped slash the number of power plants required to fuel the smart grid. Keep this in mind when evaluating your meter options.


F. Beyond traditional metering


The uses and associated value of smart meters are growing, including applications extending beyond traditional revenue billing. For example meters, and meter communications, are now being used as distribution voltage sensors for outage and restoration management, as well as for connectivity to distribution network edge devices.  In order to support these emerging applications, the following meter and communications features are important.


20. Does it have accurate and flexible voltage monitoring and does it store profiles in non-volatile memory? Accurate and flexible voltage monitoring is one of the more important applications of meters.  Meters must measure voltage accurately and need to be able to detect changes using programmable thresholds with event logging and notification.  Voltage profiling stored in the meter’s non-volatile memory is also essential for post-event analysis.


21. Does it have flexible communications include remote reprogramming? Meters need communication flexibility to allow transport of appropriate messages based on the application.  They should also offer the ability to be remotely and securely reprogrammed, especially for communications capability and protocols. This is particularly important as the applications of technology evolve.


22. Does it have robust security? Meters and metering communications modules must support robust data security capabilities, including encryption and as well as segregation of differing types of data traffic.  This is increasingly important as distribution applications more tightly converge with traditional revenue metering.


All meters are not created equal


Many in the industry assume that all smart meters are more or less alike: a smart meter is a smart meter is a smart meter. In truth, their design, construction, testing and production lead times can vary. Moreover, as the source of most of the data, the measurement interface with your customer and the part of the system where you’ll make the biggest financial investment, they’re the most critical component of your AMI deployment and one of the most important choices you’ll make.


Buyer beware. And be smart.


Jeff Richardson is Senior Product Manager - Electricity Metering, Elster Solutions. He is the product manager responsible for Elster’s electricity metering product line. He has served on several industry technical committees, including the ANSI communication protocol committee and Measurement Canada joint working groups on firmware updates and VA calculation methods. Jeff has worked on metering and utility solutions in Canada and the United States since 1991.  He played a key role in the success of the Ontario Smart Metering Initiative, the world's largest deployment with daily interval data reads from every meter. Jeff holds an engineering degree from the University of Toronto, and is registered as a professional engineer in the province of Ontario.


Elster Solutions is the North American electricity business unit of Elster, a multi-national, 7500-person company providing electricity, gas and water meters and related communications, network and software solutions to customers in more than 130 countries. Headquartered in Raleigh, NC, Elster Solutions is focused on delivering the vital connections utilities need to achieve the greatest possible value from their meter data. 


Earlier installments from the ultimate guide to AMI...

The secret to unlocking the value of meter data (Hint: a new kind of workflow)

How to cash in on smart meters for smarter outage management

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