MONITORING & METERING Figure 2. A comparison


between open-loop and closed-loop systems


with mSure technology


compared to the sensor used in the system. It is possible to activate an autocalibration


function at any time. The calibration data is composed of the gain of the current and voltage measurement chains. mSure technology can extract this data with high precision without having to resort to expensive calibration benches. Self- calibration starts by connecting the meter to a voltage source. The presence of a load is optional. Once a smart meter is equipped with mSure


current transformer must provide shielding or other protection mechanisms to avoid tampering. Hall effect sensors have excellent frequency


response and can measure high intensity currents. However, these advantages are mitigated by high temperature drift, which requires system calibration at several points for the required precision to be obtained. Like the current transformer and the Hall effect


sensor, the Rogowski coil is intrinsically isolated. The Rogowski coil is an inductor mutually coupled with a conductor through which the current to be measured flows. The magnetic coupling takes place via the air core and therefore does not introduce the typical saturation problems of ferromagnetic materials. The peculiarity of the Rogowski coil is that the signal generated by the sensor is proportional to the derivative of the current and thus requires an integrator to reconstruct the original signal. To achieve a wide dynamic range and high


linearity, and for the ability to measure very high currents, current sensing with a Rogowski coil requires the use of a stable integrator. Additionally, the Rogowski coil is particularly susceptible to external fields that allow manipulation of the power measurement through the end user.


THE NEXT GENERATION OF SMART METERS A smart meter must be able to perform its function accurately for a relatively long period of time, which can exceed ten years. A good design and the stability of the silicon electronic components make it possible to maintain high levels of accuracy for many years. However, environmental events such as lightning, a current spike, or a voltage transient can permanently alter the performance of the sensors. Without an advanced diagnostic system, such effects are difficult to detect, if at all. mSure, a new meter diagnostics


technology developed by Analog Devices, makes it possible to check the status of the measurement chain in real time and to protect against the environmental effects at the sensor. mSure technology is immune to environmental effects and can detect manipulations through diagnostics. The operating principle of mSure


technology is illustrated in Figure 2 (above). A standard meter works in open loop without a feedback path. The currents and voltages are converted by sensors,


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there is a processing chain that adds a gain and, finally, there is an analog-to-digital conversion with the extraction of data directly in the digital domain. Each component contributes to the total error; end- of-line calibration is used to compensate for the initial error and ensure that the meter stays within the specifications for a specific accuracy class. For a standard meter, once installed in the field,


the only way to test its accuracy is to physically remove it for laboratory testing. A less intrusive alternative is to verify the performance of a production batch, but this is costly. In contrast with a standard meter, a meter


equipped with mSure technology allows real-time accuracy verification in the field through a more complex, closed-loop system, as shown in Figure 2. The closed-loop system includes the addition of a reference block that generates a stable and very precise signal to be injected on the sensor. This signal crosses the whole measurement chain and is picked up from the detection block. The entire signal chain is monitored in real time, capturing any errors (like gain, drift, etc.), and allowing for continuous calibration to adjust for these errors. Additionally, one of the greatest advantages of mSure technology is the detection of fraud. Since most tampering consists of altering the gain of the measurement chain, mSure can instantly detect this change, unlike an open-loop system. mSure is non-intrusive and can be activated while


the meter is running. To ensure an accurate reading, an appropriate block detects and deducts an mSure device’s contribution to the final energy measurement. The accuracy of the meter thus depends on the accuracy of the reference block. The reference has, by definition, a better accuracy


technology and installed in the field, you can check the accuracy of the meter continuously or at predetermined time intervals. If a meter has an accuracy drift, it is possible to correct the calibration data so that the energy count is accurate. So far, government regulations do not allow the calibration data to be changed in the field for standard meters. With mSure technology, the utilities will be able to intervene promptly where needed and, in case of extended intervention, will have an accurate estimate of the difference in energy. The ADE9153B and ADE9322B are mSure-enabled


energy metering ICs with sensor monitoring and self-calibration for the next generation of smart meters from Analog Devices.


ENERGY ANALYTICS STUDIO The mSure portfolio comes with Energy Analytics Studio (EAS). EAS is the cloud analytics service that supports mSure technology, verifying the health of each meter (health monitoring) and, ultimately, protecting revenues. The mSure Manager software, which runs on the system microcontroller, reports data related to meter parameters. The reporting frequency can be established by the operator. mSure Manager allows you to check the status of a single meter, all meters belonging to a certain geographical area (for example, those that have been subject to some extraordinary weather event), or all the meters belonging to a certain production batch.


REAL-TIME DIAGNOSTICS The innovative mSure technology enables the real-time diagnostics of electricity meters in the field. Combined with Energy Analytics Studio, it can monitor meter health, eliminating the necessity for interventions to cases of actual failure, and prevent fraud. The result is economic savings for the utilities by limiting losses through optimal meter management, while ultimately lengthening the average service life of the meters.


Analog Devices www.analog.com


Figure 3. Edge-to-cloud solution for electric utilities ENERGY MANAGEMENT - Spring 2022 27


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