This work presents a novel measurement method to characterize long-term and short-term variations of the LV grid impedance from 20 kHz to 10 MHz with configurable time, frequency and amplitude ...resolutions. The characterization of the grid access impedance in this frequency range is vital for the design and development of NB-PLC and BB-PLC technologies. The measurement system is valid for in-home, indoor cable networks and for the harsh conditions of the LV distribution grid, where a large input dynamic range and strong protection mechanisms against high-amplitude impulsive noises are required. Its accuracy is evaluated by comparison to a precision impedance meter for a wide set of impedance values, obtaining a maximum deviation within ±8%. First trials of the grid impedance sub-cycle variations caused by commercial appliances and for frequencies assigned to BB-PLC are also presented in this paper. The results demonstrate that the grid impedance is highly time-varying within the mains cycle, both in amplitude and phase. These first outcomes point at the need to evaluate the accumulative effects of sub-cycle variations in the LV distribution grid, so that equalization algorithms in the next BB-PLC technologies could be developed to overcome the impact of these fast variations.
Synchronized phasor measurements are becoming an important element of wide area measurement systems used in advanced power system monitoring, protection, and control applications. The recently issued ...revised standard C37.118 for synchrophasors has facilitated interoperability of phasor measurement units (PMUs) from different manufacturers. This standard defines performance for compliance when the input signals are in steady state. The performance of PMUs under transient conditions is not considered by the standard at this time, although clearly PMUs will be subjected to inputs under transient conditions. This paper is an attempt to provide the authors' views on how one may approach the question of standardizing PMU response under transient conditions.
Accurate measurement of losses in magnetic components and the resulting temperature behavior is essential for device characterization and thermal model validation. However, some factors such as the ...significant phase displacement angle between voltage and current, and the practical challenges of measuring high-frequency electrical quantities need to be considered when choosing excitation equipment, probes, and assembling test setups. This work proposes an experimental and non-invasive procedure for acquiring temperatures of magnetic components in stagnant air with prescribed constant input power. The electrical modeling of the system, the choice of suitable equipment and probes for measuring losses, the structure of the system, pre-test procedures, and other system components are discussed in detail. The validation of the procedure and the experimental setup was performed through testing of E-core and toroidal inductors, altogether with computational fluid dynamics (CFD) simulations for an extended range of power losses. Finally, the results presented an excellent agreement, proving that the proposed methodology is a reliable tool for assessing the thermal behavior of magnetic components.
The multinode multibaseline interferometric synthetic aperture radar measurement system is the future development trend in the field of aviation remote sensing. The deformation error between the ...nodes directly affects the position and orientation error compensation of the load at the node, and the baseline length error directly affects the interferometric phase error compensation. Aiming at the particularity of the wing structure, a structural deformation measurement and baseline measurement method based on the strain mode is proposed. The fiber Bragg grating sensor is used to acquire the strain of each measuring point on the wing in real time, and the deformation of the wing is accurately measured by the modal superposition method, thereby realizing the high-precision measurement of the baseline between the nodes. The measurement result of the dual total station is the benchmark, and the validation of the method was carried out on the existing test system in the laboratory. Under static conditions, the experimental test results show that the wing deformation measurement accuracy is better than 1 mm, and the baseline measurement accuracy is better than 0.5 mm.
This paper presents a novel noncontact measurement technique that entails using a single-compound triple complementary split-ring resonator (SC-TCSRR) to determine the complex permittivity and ...thickness of a material under test (MUT). The proposed technique overcomes the problem engendered by the existence of air gaps between the sensor ground plane and the MUT. In the proposed approach, a derived governing equation of the resonance frequencies is used to estimate the thickness and complex permittivity of the MUT by calculating the resonant frequency (f r) and magnitude response in a single-step noncontact measurement process. This study theoretically analyzed and experimentally verified a simple and low-cost SC-TCSRR measurement method for assessing materials in a noncontact method. For a 0.2-mm air gap, the experiments yielded average measurement errors of 4.32% and 5.05% for the thickness and permittivity, respectively. The proposed SC-TCSRR technique provides excellent solutions for reducing the effect of air-gap conditions on permittivity, thickness, and loss tangent in noncontact measurements.
This paper presents a new method for online determination of the Thèvenin equivalent parameters of a power system at a given node using the local PMU measurements at that node. The method takes into ...account the measurement errors and the changes in the system side. An analysis of the effects of changes in system side is carried out on a simple two-bus system to gain an insight of the effect of system side changes on the estimated Thévenin equivalent parameters. The proposed method uses voltage and current magnitudes as well as active and reactive powers; thus avoiding the effect of phase angle drift of the PMU and the need to synchronize measurements at different instances to the same reference. Applying the method to the IEEE 30-bus test system has shown its ability to correctly determine the Thévenin equivalent even in the presence of measurement errors and/or system side changes.
Dynamic measurement precision assessment has been achieved for a differential circle measurement application. Differential circle diameter measurement, in image analysis, typically requires fitting a ...circle model that optimizes for image distortions, defects or occlusions. The differential task occurs when precise measurements of diameter change are required given object size variation with time. An automated system was designed to provide diameter measurements and associated measurement precision of images of a fuel droplet undergoing combustion in zero gravity for the FLEX-2 dataset. An image gradient-based, least-squares boundary point fitting method to a circle or ellipse model is used for diameter measurement. The presence of soot aggregates poses significant challenges for diameter measurements when it occludes part of the droplet boundary. The precision of the diameter measurements depends upon the image quality. Using synthetic image simulations that model the soot behavior, we developed a model based on image quality measures that assesses the measurement precision for each individual diameter measurement. Thus, diameter measurements with precision assessments were made available for follow-up scientific analysis. The algorithm's success rate for measurable runs was 98%. In cases of limited occlusion, a measurement precision of ±0.2 pixels for the FLEX-2 dataset was achieved.
The integrated photonic technologies benefit from an improved frequency measurement range with compact size relative to the radio frequency counterparts. Nevertheless, the measurement methods are ...generally limited by a basic trade-off between the measurement range and accuracy. In this work, we break the above limitations and trade-off based on a Mach-Zehnder interferometer (MZI) coupled ring array and a two-step measurement method. The experimental results show that a wide measurement range of 40 GHz and an ultra-low error of 9 MHz could be obtained. Moreover, owing to the ring flexibly tunable bandwidth and resonant wavelength, the measurement range and accuracy could be significantly adjusted. Another frequency measurement range of 20 GHz with a lower error of 4 MHz is also demonstrated. To the best of our knowledge, among the silicon-based measurement schemes, it is a record estimation error with such a wide range. With the dominant advantages of CMOS-compatibility, a broad measurement range, ultra-low estimation errors and adjustable measurement performance, the proposed microwave measurement scheme has many important applications in on-chip microwave systems.
This paper proposes a new hybrid state estimation (SE) model where the supervisory control and data acquisition (SCADA) and phasor measurement unit (PMU) measurements are decoupled. The proposed ...hybrid SE can effectively handle different accuracy levels of PMU and SCADA measurements which is a problem for conventional hybrid SEs due to increasing the condition number of SE gain matrix. In addition, the proposed hybrid SE model is fully compatible with PMU measurements, particularly current measurements, which increase the complexity of conventional hybrid SE formulation. The proposed hybrid SE model is tested on the IEEE 118-bus test system as well as on the real-world Iran's power system. Moreover, the proposed hybrid SE is compared with conventional hybrid SE using a large number of scenarios modeling uncertain telemetry noises. The comparative results illustrate better performance of the proposed hybrid SE than conventional hybrid SE in terms of the gain matrix condition number, SE run time, and SE accuracy.
Real-time monitoring of distribution systems has become necessary, due to the deregulation of electricity markets and the wide deployment of distributed energy resources. To monitor voltage and ...current at sub-cycle detail, requires, typically, major investment undertaking and disruptions to the operation of the grid. In this work, measurements of the low voltage (LV) side of distribution transformers (T/F) are used to calculate in real time the waveforms of their medium voltage (MV) sides, based on a mathematical model of said T/F. This model is, essentially, the digital twin of the MV side of the T/F. The method calculates T/F MV waveforms of voltage and current, and active and reactive power as accurately as an instrument T/F, captures all harmonics content, is unaffected by asymmetrical loading and identifies most system faults on the MV side of the T/F. The digital twin method enables monitoring of distribution T/F that avoids MV instrumentation, does not suffer in accuracy and may be readily deployable. Field data from an actual MV-LV T/F, agree with simulation results showcasing the efficacy of the digital twin method.
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