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The need to monitor the power network is leading to a significant increase in the number of measurement points. These points consist of intelligent electronic devices and instrument transformers (or more in general sensors). However, as the number of devices increases, so does the demand for their characterization and testing. To this end, the authors formulated a new characterization procedure that offers numerous benefits for manufacturers and system operators. These benefits include: (i) reducing testing time (thus lowering costs), (ii) simplifying the existing procedures, and (iii) increasing the number of tested devices. In this study, to complete the validation of the proposed characterization procedure, the authors performed a comprehensive uncertainty evaluation. This included the identification and analysis of the uncertainty sources, the implementation of the Monte Carlo method to obtain the statistical parameters of the quantities of interest, and the final method assessment according to the obtained results. Each step is described in detail, and the results allow one to (i) replicate the uncertainty analysis on other types of instrument transformers and (ii) implement the proposed harmonic characterization procedure with the confidence that the method is accurate, flexible, and scalable. [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources, electric vehicles, and other electrical assets has introduced complexities in monitoring and controlling power networks. Consequently, numerous grid nodes have been equipped with sensors and complex measurement systems to enhance network observability. Additionally, real-time power network simulators have become crucial tools for predicting and estimating the behavior of electrical quantities at different network components, such as nodes, branches, and assets. In this paper, a new user-friendly model for Rogowski coils is presented and validated. The model's simplicity stems from utilizing information solely from the Rogowski coil datasheet. By establishing the input/output relationship, the output of the Rogowski coil is obtained. The effectiveness and accuracy of the proposed model are tested using both simulations and commercially available Rogowski coils. The results confirm that the model is simple, accurate, and easily implementable in various simulation environments for a wide range of applications and purposes. [ABSTRACT FROM AUTHOR]

Conducted emissions (CE) for three-phase systems are becoming an increasing concern due to the recent exponential growth of three-phase applications, especially linked to the automotive sector. The problem arises because electromagnetic compatibility (EMC) standards only define the methodology to measure the CE generated by the equipment under test (EUT), and they do not provide sufficient information to design a power line filter (PLF) in case of non-compliance. Hence, the design of an optimal PLF is a very difficult task for engineers. The unclear methodology to be followed, unknown load impedances, inadequate equipment, and lack of knowledge of the modal noise are all different reasons that contribute to increasing the PLF design complexity. Common mode (CM) and differential mode (DM) decomposition and PLF design techniques for single-phase EUTs are well discussed and studied in the literature, but the same cannot be stated when it comes to three-phase PLF design. The objective of this paper is to clarify how modal noises behave in a three-phase system and to propose a clear methodology which can be followed to design an optimal three-phase PLF. Additionally, this paper analyses and discusses the modal noises' intrinsic behavior and provides an understanding of how the PLF components behave when subjected to either a CM or DM noise. Finally, a methodology to design a three-phase PLF, based on accurate insertion loss (IL) estimations and S-parameter measurements, is used to determine the optimal PLF. This approach is tested and validated. [ABSTRACT FROM AUTHOR]

Power system stability is a task that every system operator (SO) is required to achieve daily to ensure an uninterruptible power supply. Especially at the transmission level, for each SO it is of utmost importance to ensure proper exchange of information with other SOs, mainly in case of contingencies. However, in the last years, two major events led to the splitting of Continental Europe into two synchronous areas. These events were caused by anomalous conditions which involved in one case the fault of a transmission line and in the other a fire outage in proximity to high-voltage lines. This work analyzes these two events from the measurement point of view. In particular, we discuss the possible impact of estimation uncertainty on control decisions based on measurements of instantaneous frequency. For this purpose, we simulate five different configurations of phasor measurement units (PMUs), as characterized by different signal models, processing routines, and estimation accuracy in the presence of off-nominal or dynamic conditions. The objective is to establish the accuracy of the frequency estimates in transient conditions, more specifically during the resynchronization of the Continental Europe area. Based on this knowledge, it is possible to set more suitable conditions for resynchronization operations: the idea is to consider not only the frequency deviation between the two areas but also to take into account the respective measurement uncertainty. As confirmed by the analysis of the two real-world scenarios, such an approach would allow for minimizing the probability of adverse or even dangerous conditions such as dampened oscillations and inter-modulations. [ABSTRACT FROM AUTHOR]

Even though today's electromagnetic compatibility (EMC) standards and measurement techniques set specific limitations and a clear methodology to measure the conducted emissions (CE) of equipment under tests (EUTs), the design methodology of a suitable power-line filter (PLF) to solve non-compliance is, in general, neither accurate nor efficient. This is due to different reasons, such as unknown actual load and line impedances, unknown dominant mode in the CE, and/or inappropriate instrumentation for the appropriate measurements. The objective of this paper is to investigate if different topologies of switching mode power supplies (SMPSs) lead to different PLF structures. For the sake of exemplification, the analysis is focused on switched-mode DC-DC converters. From an EMC point of view, these devices can be completely modeled by means of Scattering (S)–parameter and CE measurements. Additionally, an analysis of their circuit models has been performed to allow a better comprehension of their characterization. In this paper, the circuit models of three different types of DC-DC converters are presented, and their component values (including nonlinearities and parasitic effects introduced by the actual behavior of the circuit elements) are estimated using the S-parameter characterization. Then, a new methodology for PLF design, based on accurate insertion loss (IL) estimations, is applied to obtain the optimal PLF for one of the converters. This methodology is experimentally tested and validated. [ABSTRACT FROM AUTHOR]

Electrical utilities and system operators (SOs) are constantly looking for solutions to problems in the management and control of the power network. For this purpose, SOs are exploring new research fields, which might bring contributions to the power system environment. A clear example is the field of computer science, within which artificial intelligence (AI) has been developed and is being applied to many fields. In power systems, AI could support the fault prediction of cable joints. Despite the availability of many legacy methods described in the literature, fault prediction is still critical, and it needs new solutions. For this purpose, in this paper, the authors made a further step in the evaluation of machine learning methods (ML) for cable joint health assessment. Six ML algorithms have been compared and assessed on a consolidated test scenario. It simulates a distributed measurement system which collects measurements from medium-voltage (MV) cable joints. Typical metrics have been applied to compare the performance of the algorithms. The analysis is then completed considering the actual in-field conditions and the SOs' requirements. The results demonstrate: (i) the pros and cons of each algorithm; (ii) the best-performing algorithm; (iii) the possible benefits from the implementation of ML algorithms. [ABSTRACT FROM AUTHOR]

This paper suggests a simple eye-brain model for light flicker studies and examines the response of such a model to voltage flicker. Calculated flicker curves representing the objectionable threshold of voltage fluctuation were found to match reasonably well the experimental IEEE curves. The model may be used to predict flicker curves for diverse voltage flicker waveforms and for lamps with different time constants and gain factors. Index Terms--Flicker, power quality.

International technical committees put considerable efforts into the writing process of standards. They always try to find a tradeoff between the rigorous scientific requirements and the practical needs of manufacturers and final users. In addition, researchers keep investigating to improve the existing standards with new procedures, achievements, and findings. The purpose of this work is to contribute to that direction. It introduces a simplified and low-cost procedure to test low-power voltage transformers (LPVTs). The procedure is designed to assess the immunity of LPVTs when subjected to external electric fields. The need for this procedure comes from the existing immunity test, which is efficient but sometimes difficult to implement. The proposed one, instead, is simpler, cheaper, does not require the application of the rated voltage, and can be replicated at all voltage levels. In the paper, the procedure is described and demonstrated with experimental tests. From the results, it is possible to appreciate the validity of the proposed solution and the different ways it could be developed, implemented, and improved. [ABSTRACT FROM AUTHOR]

The distribution network is experiencing a massive deployment of intelligent electronic devices (IEDs) such as energy meters, protective devices, and phasor measurement units (PMUs). This phenomenon resulted, on the one hand, in (i) the availability of distributed measurement systems capable of monitoring and collecting measurements from the distribution network, and (ii) increasing awareness of the system operator about the status of the network. On the other hand, such a significant number of devices require to be characterized, over the years, and assessed in both sinusoidal and distorted conditions. However, the characterization process may require a huge investment of money and time considering the low availability of reference instruments and accredited laboratories. To this purpose, this paper presents a simple and fast test procedure, performed with cheap and low-voltage instrumentation, to characterize two off-the-shelf low-power medium-voltage sensors in the power quality frequency range. In detail, the paper describes the measurement setup developed for the characterization and the performed tests. In addition, the method was also reproduced with reference equipment for validation purposes. Lastly, for both tests, an uncertainty evaluation was performed to quantify the goodness of the proposed method. From the results, it is possible to appreciate that the designed cheap and simple test can achieve as accurate results as those of a sophisticated and expensive equipment. [ABSTRACT FROM AUTHOR]

Rogowski coils are key measurement instruments in several applications due to their flexibility, large bandwidth, linearity, and so on. Like the majority of the instrument transformers (ITs), Rogowski coils are standardized and their use is regulated almost for every application. This article focuses on a smart way for the equivalent parameters’ computation of the Rogowski coil. The parameter computation is performed by evaluating the Rogowski response when subjected to a single waveform generated to fulfill a specific requirement on its frequency content. Results demonstrate the equivalency of the presented method compared to the typical frequency sweep test. In addition, the results have been used to validate Rogowski’s output estimate procedure presented by the authors in a previous work. [ABSTRACT FROM AUTHOR]

The estimations of amplitude and phase are of great importance in the synchronous phasor measurement for power systems. In addition to the off-nominal frequency, the amplitude and phase estimations accuracy level of the power system signal is affected by the inevitable noise. In this article, the effect of white noise on amplitude and phase estimations provided by DFT-based frequency shifting and filtering algorithm (FSF) is analyzed. With the help of the equivalent weighting filter’s merits, i.e., equivalent noise bandwidth and overlap correlation, the FSF-based amplitude and phase variance expressions are derived theoretically by considering the overlap of two processed samples. The effectiveness of the proposed amplitude and phase variance expressions are verified through computer simulations. [ABSTRACT FROM AUTHOR]

The frequency shifting and filtering (FSF) algorithm, a variant of DFT, has the merit of high efficiency for frequency analysis thanks to its simple implementation in the time domain. However, the inevitable white noise injected by various factors leads to inaccurate frequency estimation in practical measurement. This article investigates the influence of a stationary white noise on FSF-based frequency estimation of the power system. The variance expression of the frequency estimator is derived theoretically and compared to its unbiased Cramer–Rao lower bound (CRLB). The obtained results are validated by several computer simulations. [ABSTRACT FROM AUTHOR]

In the past years, strong changes of power network architectures and operation have led to make use of huge quantities of instrumentation, spread around the grid. In fact, there is a strong need to perform very accurate measurements of electrical quantities in many nodes of the network, mainly due to the strong penetration of distributed generation. Recently, the main Italian utility has also asked for such kind of instrumentation. Its main feature must be to perform accurate measurements in all actual conditions. Such conditions include the instrumentation operation during the off-nominal condition of the network. To this purpose, in this paper, a low-cost acquisition system (AS) developed by the authors is recalled. Then, a full comparison with off-the-shelf products during ideal or not power source is provided. The obtained results highlight the potentialities of the developed system for its implementation in both laboratory or medium-/low-voltage (MV/LV) networks. [ABSTRACT FROM AUTHOR]

This paper addresses one of the new and most important issues arising when low-power voltage transformers (LPVTs) are used in power network substations for evaluating, among others, the residual voltage measurement. Conversely to open-triangle inductive instrument transformers, the use of phase voltage transformers for measuring the residual voltage gets challenging due to the very high accuracy required for the three LPVTs. In this paper, a general expression to estimate the residual voltage measurement uncertainty, starting from the LPVTs accuracy, is presented. The effectiveness of the proposed approach is then confirmed with both Monte Carlo simulations and actual measurements on a general three-phase system. [ABSTRACT FROM AUTHOR]

As a reliable power network is crucial to deliver promised electric power, cable powerline monitoring in medium-voltage networks has a great importance for distribution system operators all over the world. A considerable rate of failures in cable powerlines is referred to the cable joints. Especially during the summer period, an excessive number of joints are subjected to explosion, causing outages in different points of the power network. To this purpose, in this paper, using a simple test setup presented in a previous work, the effects of temperature on the cable joint tan delta measurement have been evaluated. In fact, the temperature is one of the possible causes of faults and, from the patterns presented in the results, the hypothesis seems to be confirmed. [ABSTRACT FROM AUTHOR]

Rogowski coils are key measurement instruments in several applications due to their flexibility, large bandwidth, linearity, and so on. Like the majority of the instrument transformers (ITs), Rogowski coils are standardized and their use is regulated almost for every application. This article focuses on a smart way for the equivalent parameters’ computation of the Rogowski coil. The parameter computation is performed by evaluating the Rogowski response when subjected to a single waveform generated to fulfill a specific requirement on its frequency content. Results demonstrate the equivalency of the presented method compared to the typical frequency sweep test. In addition, the results have been used to validate Rogowski’s output estimate procedure presented by the authors in a previous work. [ABSTRACT FROM AUTHOR]

The estimations of amplitude and phase are of great importance in the synchronous phasor measurement for power systems. In addition to the off-nominal frequency, the amplitude and phase estimations accuracy level of the power system signal is affected by the inevitable noise. In this article, the effect of white noise on amplitude and phase estimations provided by DFT-based frequency shifting and filtering algorithm (FSF) is analyzed. With the help of the equivalent weighting filter’s merits, i.e., equivalent noise bandwidth and overlap correlation, the FSF-based amplitude and phase variance expressions are derived theoretically by considering the overlap of two processed samples. The effectiveness of the proposed amplitude and phase variance expressions are verified through computer simulations. [ABSTRACT FROM AUTHOR]

This paper deals with the accuracy evaluation of a method for gathering synchronized phasor measurements of electrical quantities in nodes of power networks. Usually, this task is performed using commercially available instrumentation, for instance, the phasor measurement unit. They rely on a common time reference signal provided usually by the GPS system. After a brief recall of two methods already presented by authors in previous papers, which do not require a common time reference for providing synchronized phasors of voltages at the network nodes, the major sources of uncertainty in the measurement chain (lengths of the branches of the network; per-unit length reactance of the cables; and effect of the instrument transformers) are considered and investigation on their contribution, in one of the two methods, to the overall uncertainty performed. [ABSTRACT FROM AUTHOR]

This paper deals with the evaluation of the accuracy performance of an approach for assessing the phase displacement between voltages at power network nodes. This task is accomplished by processing asynchronous measurements taken at each node. This turns into an equivalent synchronization, which is, therefore, obtained without exploiting any synchronization signals, such as the ones provided by means of wireless (i.e., global positioning system) or wired technologies. As a matter of fact, distribution system operators will gain the possibility of deploying, at more affordable costs, wide area measurement system (WAMS) over their power networks for enhancing their stability and reliability. Phasor measurement units (PMUs) are the most common examples of such WAMS, but, besides their high cost, there are circumstances where providing a time reference signal to remote PMUs often becomes a difficult task. This paper aims at recalling the basic theoretical principles of the method and at proving its applicability in power network through a deep analysis of its metrological performance. [ABSTRACT FROM AUTHOR]

This paper presents the study of the propagation of the effects of uncertainties in a typical measurement system for modern power networks. Nowadays there is a strong demand from the electricity industry of simple and ready-to-use solutions for calculating uncertainty in such “new” measurement systems. To this purpose a simplified approach is presented whose results are shown to be in good agreement with those provided by conventional but more complex methods. Two applications, rather simple but very common, are considered in this paper. In the first one, the measurement of a voltage phasor is considered and the measurement chain is made by an low power instrument transformer (LPIT) and a converter used for adapting the level of signals from the LPIT to the inputs of intelligent electronic device. The second application deals with the measurement of active power of a system made by a low power voltage transformer (LPVT), a low power current transformer and a powermeter. [ABSTRACT FROM AUTHOR]

Medium-voltage cable joints are one of the critical components of the distribution networks. They represent the first cause of faults and outages. Among the others, partial discharge, dielectric, and temperature measurements are the typical tests performed for investigating over the early aging of such critical components. In this paper, a new study has been completed correlating the cable joint tangent delta (Tan $\delta$) value to the external pressure applied on the insulating material surrounding the joint. Results confirm the presumed correlation. In fact, an increase of pressure results in a Tan $\delta $ decrease, hence in an extension of the cable joint working life. [ABSTRACT FROM AUTHOR]

In this paper, the measuring and calibration techniques useful for ensuring the traceability of nonconventional voltage transformer (VT), used in ac power plant up to 52 kV, are described and discussed. In particular, a setup made by commercially available devices is presented and an in-depth accuracy analysis is performed by considering all the uncertainty sources located in the measurement chain. The obtained results prove that it can be used for the calibration of 0.5 accuracy class low-power VTs. In addition, the sources that contribute more to the uncertainties on the ratio and phase errors are highlighted and suggestions on where to act to further improve the accuracy of the presented setup are given. [ABSTRACT FROM AUTHOR]

This paper illustrates the development and the experimental validation of a life model for light emitting diodes (LEDs) able to predict the time to failure under different stress conditions associated with the value and time dependence of applied forward current. In the paper, three different life models are derived by exploiting the results of tests under constant forward current. Then, experiments performed by subjecting LEDs to simple load cycles characterized by step-varying forward current are carried out, and the results are employed as a benchmark for the predictions provided by the combined use of the life models derived under constant stress and cumulative damage theory. [ABSTRACT FROM AUTHOR]

Efficiency of power conversion apparatus must usually be measured with very low uncertainty, and depending on the kind of apparatus under test and on the measurement method applied, more or less accurate instrumentation is required. The main issues to be faced, once the target uncertainty is fixed, concern the choice of the measurement method as well as the instruments to be used for fulfilling such requirement. This paper investigates by means of both theoretical analysis and experimental results on the relationship between target uncertainty and instrumentation accuracy in the measurement of uninterruptible power supply efficiency. The results show, amongst other things, that the measurement method allows obtaining very low uncertainty values by means of low accuracy instrumentation. [ABSTRACT FROM PUBLISHER]

Current measurement is required to ensure the correct operation of power systems. Conventional current transformers are still widely employed in such networks, but their well-known limits make them not suitable for the incoming smart meters. In this paper, a current sensor based on proper measurements of the magnetic field produced by the primary current is proposed. Its main feature is the capability, owing to its particular geometry, of neglecting the effect of external fields without using traditional coil structure. An experimental analysis of its performance in both time and frequency domains is presented and discussed. [ABSTRACT FROM PUBLISHER]

Flicker severity is a parameter defined in the Standard EN 50160 that involves both power quality and physiological features. Due to practical and theoretical reasons, the flickermeter described by the relevant International Standard may lead to incorrect results when used to correlate voltage variations with annoyance caused by fluctuations of light emitted by other types of lamps different from those based on the incandescent-filament principle. Therefore, its replacement is under consideration by some international organizations, given that this last type of lamps will no longer be available on the market starting next year. This paper aims at providing a contribution to the study of a new theory to be used for the design of next-generation flickermeters that must account for a wider variety of luminous sources. In particular, the research is focused on finding a new method for detecting human being annoyance in the presence of luminous flicker that is based on the measurement of the pupil diameter under flicker conditions. In this connection, this paper first investigates on the performance of an ad-hoc test system with the main goal to prove and evaluate its accuracy. Then, the results of tests on six volunteers are presented and discussed. [ABSTRACT FROM AUTHOR]