This paper presents a novel approach for integrating an analytical model of Rogowski coils (RC) directly within microcontroller-based systems to enable local verification of acquired signals and facilitate digital twin implementation at the embedded level. The proposed method embeds a simplified yet accurate coil model into the microcontroller’s firmware, allowing real-time comparison between measured and expected signals. This verification process helps detect deviations caused by network anomalies, coil accuracy degradation, or acquisition issues. The concept is validated experimentally by injecting reference signals into the system and comparing the microcontroller-acquired data with the model’s predictions. This embedded verification mechanism supports adaptive configurations depending on the available computational power, number of channels, and coil characteristics. By demonstrating how digital twins can be implemented and maintained even on low-resource platforms, this work offers a flexible and scalable framework for improving the reliability and intelligence of current-sensing systems in distributed measurement applications. Moreover, the approach is generalizable and may serve as a foundational technique for digital twin design across a broad range of sensor-based monitoring systems.
Phase-Locked Loops (PLLs) play an essential role in a variety of power grid applications and measurement devices. Unfortunately, PLL performance analysis and design are often hindered by their inherent nonlinear nature that cannot be adequately described by standard linearized models. To address these issues, this paper presents a two-step modeling approach. First, a Linear and Time-Periodic (LTP) model is applied. Then, a variant of the harmonic balance method is applied to turn the LTP model into a Linear Time-Invariant (LTI) one, whose smallsignal dynamics can be potentially used to analyze the system behavior of terms other than the fundamental one. The proposed methodology is applied to an advanced three-phase PLL scheme based on an Orthogonal System Generator (OSG) followed by a pair of Mixed Second- and Third-Order Generalized Integrators (MSTOGIs), which provide not only harmonics attenuation, but also DC offset cancellation and imbalance mitigation. Some simulation results under different testing conditions, confirm that the obtained model is very accurate, thus paving the way to optimal PLL design in different power grid applications using standard linear system tools.
Fiber-optic current sensor (FOCS) technology offers intrinsic galvanic isolation, a wide linearity range, immunity to electromagnetic interference, and non-invasive measurement, making it a strong candidate for applications in on-site calibration. However, its use as a traceable reference in metrological applications remains limited so far. Laboratory calibration and cross-institutional comparisons are essential steps toward establishing the reliability and traceability of FOCS in real-world conditions. This paper provides an overview of the FOCS operating principle and evaluates the key performance of a new FOCS sensor tested in two National Metrology Institutes (NMIs), including accuracy, stability, linearity, and temperature dependence. It furthermore describes the on-site measurement campaign using the FOCS for efficiency measurement in a medium-voltage substation. The test results reveal that FOCS can meet the performance requirements under practical conditions and demonstrate excellent repeatability and traceability for on-site calibration in operational environments: the linearity is better than $0.1 \%$ over the 2.4 kA current range, with temperature effects less than $0.2 \%$ from -10 to 60 degrees Celsius. This work contributes to understanding the metrological characteristics of FOCS and supports their broader adoption in on-site calibration.
Harmonic current summation is used by transmission system operators to quantify the global contribution of distribution networks hosting distortion sources. An increase of renewable power plants (non-linear current sources) and the over subscription of hosting capacity in distribution networks, could be a concern in containing THD within compatibility levels. IEC 61000-3-6 use RMS values to propose summation exponents (alpha factors). By using harmonic current phasors, it is shown that alpha factors require careful consideration to produce useful results. Simulation data is first used to identify those assumptions that lead to erroneous results. RMS summation and phasor summation is then compared making use of field data. Phasor summation is shown to be practical and to improve reliability of results.
During the last decades, Medium Voltage (MV) and Low Voltage distribution systems have become increasingly complex due to the increasing penetration of Renewable Energy Sources and – more in general – distributed resources such as evehicles. Therefore, better monitoring and control tools are required. This paper discusses how Digital Twin (DT) architecture for MV distribution grids can improve management, presenting the benefits in a specific use case: State Estimation (SE). This approach has been applied to the distribution grid of Unareti S.p.A., an Italian Distribution System Operator (DSO) operating in northern Italy and serving over one million customers. The suggested architecture combines real-time field measurements, a very detailed virtual model of the physical grid, and an SE algorithm all embedded into Advanced Distribution Management System (ADMS) which is also fully integrated within a more general Information Technology/Operational Technology (IT/OT) ecosystem in order to become a DT. This DT framework enables continuous synchronization with live grid conditions, enriching network observability and improving estimation accuracy, even in areas with a low percentage of monitoring devices. The presented case study focuses on a HV/MV primary substation managed by Unareti and demonstrates the capability of the architecture to deliver real-time state estimations in a real operating environment. The mean percentage error of the SE algorithm is $-4.9 \%$ and the standard deviation is $13.3 \%$.
Modern power distribution grids are facing significant monitoring challenges from renewable energy volatility and persistent measurement scarcity. In this paper, we propose a data-driven approach for voltage magnitude estimation in distribution systems using correlated Gaussian processes. We demonstrate that the proposed approach can be applied to a variety of monitoring configurations. Comparable accuracies are achieved even when the number of monitoring units is significantly reduced. Moreover, the results are obtained with the help of small training sets, allowing for short observation periods to generate training data. The proposed approach offers flexibility in terms of monitoring configurations and provides reliable voltage estimation in poorly monitored distribution networks.
The phasor data concentrator (PDC) plays a key role in synchrophasor-based monitoring systems by collecting and aligning time-stamped data from phasor measurement units (PMUs) installed in the grid. In this context, this paper unlocks crucial potentiality of the PDC’s role, enabling it to operate as an active device capable of event detection and analysis. Based on statistical anomaly detection and matrix profile (MP) technique for similarity analysis, the proposed PDC, called d@PDC, which stands for detection at PDC level, identifies discordant patterns in PMUs data streams and assesses their possible presence also in others. This approach allows for early recognition of potentially critical operating conditions and improves situation awareness across the monitored network. In this way, d@PDC supports a local computing paradigm, generating and validating insights from distributed synchronized measurements. The proposal has been validated through both synthetic and real data from publicly available PMU datasets.
This work presents an experimental on-field case-study analysis of Standards-based metrics for supraharmonics (SHs) measurements in distribution networks. IEC 61000-4-30 FFT-based metrics, with some proposed modifications, are compared with measurements according with CISPR 16-1-2, using as reference IEC 61000-2-2 and IEC 61000-2-4 for SHs emissions limits in 9-150 kHz frequency range. Measurements have been carried out on a commercial bidirectional power electronic converter (ac/dc and dc/ac) with a battery storage system, operating in both charging and discharging mode and with different power levels. To investigate the feasibility of the proposed approach, the analysis is extended to both voltage and current waveforms. The obtained results show that, with some modifications, IEC 61000-4-30 FFT-based metrics can provide information comparable with CISPR-based measurements, in the perspective of preliminary in-situ evaluation of SHs emissions levels and without the need of sophisticated on-field instrumentation.
In power system control, the responsiveness of the measurement infrastructure can be assessed by means of several metrics. Technical specifications and product standards have introduced performance metrics such as delay time, which should account for the time necessary to react to a sudden change in the input signal. On the other hand, the trustworthiness of the measurement result should be evaluated also during abnormal conditions. In this paper, we consider two different implementations of a PMU prototype, and we assess its responsiveness in terms of two metrics: delay time and trustworthiness. To this end, we characterized the two PMU implementations by means of extensive simulated and hardware-in-the-loop tests. The preliminary results confirm that the combination of delay time and trustworthiness metrics represent a valuable input for setting up more robust and effective control routines.
This paper investigates power quality (PQ) issues in the medium-voltage network at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany. The study focuses on voltage disturbances, harmonic distortions, and flicker levels that affect sensitive research equipment. DESY currently defines the voltage quality using EN 506160 and refers to IEC 61000-3 for permissible network disturbances. Field measurements using advanced data acquisition tools revealed voltage dips, swells, and harmonics exceeding thresholds defined by IEC 61000-3 and IEEE 519. Flicker analysis indicated irregular voltage fluctuations due to dynamic load changes. Despite ongoing efforts aim to refine PQ management through updated guidelines in the DESY planning manual, the findings in this paper suggest that compliance with existing standards alone is insufficient for ensuring power stability in specialized research environments. This study provides key insights for developing proactive PQ solutions tailored to industrial facilities like DESY.
Lithium-ion batteries are the most common electrical energy sources for stationary or mobile applications. The increasing deployment of these batteries has amplified the need for accurate estimation of the battery’s state of deterioration, also known as the inverse quantity, State of Health (SoH), which is critical for ensuring reliability, safety, and optimal performance in any application. As electric vehicle (EV) technologies continue to advance, ensuring the reliability and safety of their lithium-ion battery systems is vital. Battery faults in EVs can lead to performance degradation, reduced driving range, and, in severe cases, thermal runaway and safety hazards. The process of SoH estimation and the diagnosis of faults regarding the batteries can be quite a complicated task due to their present nonlinearity. This paper proposes and evaluates a method for battery fault diagnosis and State of Health (SoH) estimation. The results of the two tests that were carried out for the validation of the method show high accuracy, a maximum error of $\mathbf{3. 9 7 \%}$ for the first one and $\mathbf{0. 6 3 \%}$ for the second one.
Testing of current Instrument Transformers relies on low-distortion wideband generation, in particular for the modern exigency of extending testing in the supraharmonic range (up to 150 kHz). Whereas single-tone amplitude accuracy and controllability has been mostly considered so far, low-distortion for non-linearity verification and transient behaviour in presence of commutating semiconductor devices are also relevant. The design of a stable, accurate and low-distortion amplifier is discussed, featuring 15 A output and sub-$\mu \mathrm{s}$ rise time in the present realization, but scalable to higher current. Design solutions were selected that can be easily replicated, including minor variants to adapt to different exigencies. Preliminary experimental results of the prototype are reported.
With the increasing penetration of renewable resources in modern power systems, the estimation of the Rate of Change of Frequency (ROCOF) has become a critical but challenging task. Conventional methods, such as the Interpolated Discrete Fourier Transform (IpDFT), assume stationary frequency components and often yield inconsistent results under distorted or transient conditions. This paper introduces a novel modification to the classical DFT formulation by incorporating a ROCOF parameter, effectively breaking the stationary frequency assumption. The proposed ROCOF-DFT method not only enhances the dynamic tracking of frequency changes but also mitigates the adverse effects of ROCOF on phasor estimation accuracy. The method was tested using signals conforming to IEC/IEEE 60255-118-1, adapted to emphasize the method’s characteristics, and compared against the classical IpDFT approach, delivering promising results. Other tests applied in the current paper demonstrate the method’s capacity to clearly distinguish between simultaneous interfering signals of differing frequencies and ROCOF values, as well as its behavior under ROCOF step tests.
The implementation of digital substations is becoming increasingly common and one of the principal elements is the stand-alone merging unit (SAMU). Therefore, the calibration of the SAMU is essential to ensure the accuracy and reliability of measurements, as the operation of the protection equipment depends on them. This study focuses on evaluating testbeds used in different laboratories to calibrate the same SAMU: CIRCE, RISE, VSL, and VTT. Following IEC 61869-13 standard, magnitude and phase displacement were calibrated on all channels for current and voltage. Additionally, the compatibility among laboratories was evaluated using a compatibility index, confirming their mutual compatibility in the calibration process.
This paper presents the development of a comprehensive measurement information integration framework designed to operate within a cross-platform software ecosystem. The proposed framework leverages open-source APIs and unified data formats to enable seamless interoperability among heterogeneous data sources, each characterized by distinct reporting rates and communication protocols. A central component of the approach is the implementation of an intelligent edge computing engine, capable of aggregating, analyzing, and correlating measurement data in real time. Through advanced data analytics, the engine supports functionalities such as anomaly detection, predictive maintenance, and dynamic energy control. These capabilities are essential for enhancing situational awareness and operational efficiency in emerging low-inertia power grids. The overall solution facilitates more reliable and optimized energy transfer by bridging the gap between diverse measurement infrastructures and control strategies in next-generation electrical networks.
Power electronic-based devices are well known for injecting conducted emissions into power grids. Among these emissions, impulsive disturbances with complex amplitude and temporal variations are particularly significant due to their potential to interfere with grid operation. However, the accurate characterization of such disturbances is often complicated by the limitations of measurement instruments, which may distort the signals due to their reception paths and digitization processes. This paper presents a methodology for synthesizing power representative impulsive waveforms that can be reproduced using quantum voltage standards, such as Josephson Arbitrary Waveform Synthesizers (JAWS). Two waveform synthesis techniques are proposed, combining mathematical modeling and Gaussian-based functions to replicate the characteristics of real-world conducted emissions. The methodology is applied to synthesize three representative impulsive waveforms previously measured in power grids. These synthetic waveforms are then compared to the measured waveforms to evaluate the goodness-of-fit and validate the accuracy of the synthesis process. The resulting test waveforms are shown to be useful for the characterization and benchmarking of commercial measurement instruments. By exposing these instruments to realistic and reproducible impulsive disturbances, their performance in capturing complex emissions can be rigorously assessed.
This paper presents an integrated approach to power quality monitoring across Italian transmission and distribution systems. The proposed methodology combines datasets from the Italian transmission system operator, Terna, and from the QuEEN monitoring system developed by RSE, which collects power quality information in terms of voltage events and variations on medium voltage busbars in primary substations. The integration enables a unified SQL-based database architecture that supports advanced statistical analysis and cross-layer event correlation. Two case studies are presented considering a 14-years observation period: i) the evaluation of the selectivity of the protection systems carried out by analyzing the number of load disconnections per failure; ii) the investigation of the correlation between high voltage outages and medium voltage interruptions recorded by QuEEN measurement units. Results highlight a gradual decreasing trend in system selectivity and a significant match between high and medium voltage events, highlighting the benefits brought by an integrated monitoring for reliability assessment and predictive maintenance.
The frequency characterization of instrument transformers is a topic of ongoing discussion, and the identification of a standardized methodology to perform it is still an open issue. Among the possible approaches discussed in international standards and literature, the use of pulse signals is particularly attractive due to the rapidity of execution and their compatibility with existing standard tests already performed on voltage transformers. In this context, this paper investigates the pros and the issue of using impulsive voltages as test waveforms for the MV voltage transformers wideband characterization. The study is conducted from both the theoretical and experimental point of view by performing preliminary tests on two commercial sensors.
The rapid transformation of modern energy systems, driven by decentralization, digitalization, and renewable energy integration, calls for adaptive and cost-effective monitoring solutions. This paper presents a customizable designed web-based tool for multi-source electrical signal monitoring and analysis, developed using Python’s Plotly Dash framework. Unlike existing platforms that rely on proprietary or high-cost ecosystems, the proposed solution emphasizes accessibility and flexibility, enabling users to visualize, tabulate, and analyze voltage and current signals from multiple acquisition nodes. The system supports both real-time measurements and simulated data, making it suitable for energy systems related to the electrical grid. In this study, data was simulated from systems incorporating active power filters (APFs), which compensate for harmonics introduced by nonlinear loads. The dashboard includes features such as dynamic plotting, tabular data inspection, harmonic analysis, total harmonic distortion (THD) computation, and power factor evaluation. Designed for researchers and small-scale energy systems, this lightweight platform demonstrates the feasibility of interactive energy monitoring using open-source tools.
Recent advance in semiconductor technology has enabled the development of power converters with higher and higher switching frequencies. Some emerging technologies allow power converters to be directly connected to Medium Voltage (MV) power grids. Consequently, high-frequency components—specifically, harmonics related to the switching frequency—will be present within MV networks. To ensure the reliable and stable operation of these grids, it is essential that such disturbances are accurately measured. This scenario enhanced performance requirements on Instrument Transformers (ITs), particularly in terms of measurement accuracy over an extended frequency range. In order to properly assess ITs’ frequency behaviour, it is crucial to implement a generation architecture, which allows to generate reduced-amplitude spectral components up to hundreds of kilohertz superimposed to the power frequency component. Such an architecture is not currently available in the market and that is a huge gap between the actual state of the art and the metrological needs which have been emerging in recent years. In this paper, a generation setup for the characterization of Voltage Transformers (VTs) in the frequency range including power frequency ($50 / 60 \mathrm{~Hz}$) and spectral components within the range $9 \mathrm{kHz}-150 \mathrm{kHz}$ is provided. The proposed architecture consists of two grounded and parallel-connected voltage generators to separate the generation of the power frequency component from the generation of high-frequency tones. Experimental results related to the working operations of the proposed architecture are discussed.
