Harmonic Measurements Research Articles

Sensor optimum location algorithm for estimating harmonic sources injection in electrical networks

Today, the presence of disturbing loads in low, medium and also directly in high voltage networks is producing a growing presence of harmonics and unbalance in transmission levels. Economic reasons difficult the installation of harmonic measurement devices in all the buses of the system. Instead, it would be possible to install harmonic measurement equipment in selected buses, in a fraction of the buses of the network. With them, estimation of harmonic current injection can be made. In this paper, a method to estimate the best buses to install harmonic voltage measurement equipment is presented. Based on the configuration of the network supplied by the TSO (by means of its impedance matrix), the method allows to determine which are the best buses. The method is being implemented for the Spanish TSO REE, to allow the watching of the harmonic and unbalanced presence in the Spanish transmission network, with the actual equipment and to determine the future equipment installation buses. It is developed by the UPM Electrical and Mathematics Departments under an investigation project (GENINF) with REE funding.

Measurement and calculation of harmonics in distribution power system with connected small co-generation facility Etan

Generation of electrical energy in large conventional plants (thermal, hydro, nuclear) in last ten years worldwide is being supplemented by small generation utilities. Etan is a gas refining facility. Power supply is provided by two turbo generators and each of them can independently cover the consumption of Etan. Etan usually works in insular operation, but it can also work parallel to the distribution system, especially in cases of maintenance of generator units. Etan is connected to the MV distribution power system (10 kV bus in substation 35/10 kV Ivanic Grad) through a 4,5 km long cable. Load in Etan consist mostly of induction motors. Power electronic devices are used for control of motor loads. The working process of the refinery is always the same so the load is not varying with time. It is very important to know the influence of this kind of industrial consumers with distributed generation on power quality. Power quality measurements were performed at three measurement points with the power quality analyzer ION 7650 of company Power Measurement. The aim of this paper is to compare harmonic measurements and calculations at all three measuring points in different operating conditions depending on the production of generator in Etan.

Performance and measurement of power quality due to harmonics from street lighting networks

The municipality government of San Miguel de Tucumán city in Argentina is interested in applying energy saving policies to street lighting facilities. In this frame, devices like astronomical programmable clocks and electronic control gear (ballast) will be used to replace photocells and inductive control gear. Also luminaries in use could be replaced by more efficient ones. A technical-economical evaluation was necessary and the technical aspect was request to the Lighting Department of Tucumán University. The performance of the devices and the power quality impact in the lighting networks evaluation was also necessary to evaluate. The study carried out involved outdoor and laboratory test. During 1,5 month six lighting networks with 273 semi-cutoff luminaires were tested. Network selected belong to residential areas which represent more than 60% of total city lighting facilities (26.000 luminaires). In addition laboratory test were conducted with a sample of inductive (in use) and electronic control gear, for high pressure sodium discharge lamps (HPS) 150W. Performance varying voltage input for aged was analyze. Some results from tests points out that: • The use of programmable astronomical clocks instead of photocell produces 11% of energy saving because of actual time on and off schedule set. • Electronic control gear instead of inductive control gear produces 28% energy saving. • Luminaire replacement of current HPS 150W by HPS 100W with Electronic control gear and photocell control produces 43% in energy saving. Outdoor test results from measurement of electrical input parameters and harmonics of existing inductive control gear in street lighting, indicate that: while THD V voltage is about 2,8%, THD A current can be reduced from 38% to 6,5% even when electronic control gear is set to the lower output power step (70% of power output and 60% of initial average illuminance value). The results obtained will be used as arguments for the widespread replacement in the city which would involve considerable investment and a new experience in the region.

Subcoercive field dielectric response of 0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3) thin film: Peculiar third harmonic signature of phase transitions and residual ferroelectricity

Subcoercive field non-linearities in 0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3) (BCTZ 50/50) thin film elaborated using pulsed laser deposition are studied using permittivity and phase angle of the third harmonic measurements as a function of the AC measuring field EAC and temperature. The global phase transition temperature Tmax for which the permittivity is maximum, decreases from 330 to 260 K when EAC increases. Rayleigh analysis of the AC field dependence of the relative permittivity shows a regular decrease in the domain wall motion contributions as temperature increases up to Tmax and an even more pronounced decrease above Tmax. This measurement reveals that the ferroelectric behavior subsists 70 K above the global phase transition. The phase angle of the third harmonic at temperatures below 275 K is characteristic of a conventional ferroelectric and from 275 K to Tmax=330 K of a relaxor. Above Tmax, the thin film exhibits a peculiar phase angle of the third harmonic, which consists of −180°→−225°→+45°→0° instead of the −180°→−90°→0° found for relaxor. This peculiar behavior is observed only on heating and is tentatively attributed to changes in the correlations between polar nanoregions.

Currents’ Physical Components (CPC) concept in wind farm harmonic current studies

Very little information about actual wind farm harmonic measurements is available in the literature. This paper analyzes the harmonic measurements of an 18 MW wind farm with the CPC concept to determine if they are consumed or injected by the wind farm and to study the different reactive power definitions. The CPC concept is an approach to power theory that provides a physical interpretation of power phenomena in electrical systems with linear, time-invariant (LTI) loads and harmonic generating loads (HGLs) such as wind farms.

Determination losses and estimate life of distribution transformers with three computational, measurement and simulation methods, despite harmonic loads

Transformers are the basic and valuable equipment of electricity network. Transformers correct function has important role in reliability of network .distribution transformers are designed for work at nominal frequency and full sinus current. Application of nonlinear loads in recent decades, such as power electronic loads, caused higher levels of harmonic. This kind of load can lead to creating heat, losses and therefore cause wear of insulation and aging of transformers. To prevent these problems, nominal capacity of transformers that will feed the nonlinear load, should be reduced. In this paper the parameters affecting the loss of a single phase 15 KVA transformers with harmonic loading measurement and will be calculated with standards then The transformers with harmonic loads are simulated in MATLAB software for calculating losses Finally, the obtained results are compared. The reduction of nominal power (Derating) and transformer life and flow rate limits and losses are calculated.

Background harmonic distortion measurement at power networks with wind farms

Standard IEC 61400-21 specifies that background voltage distortion must be lower than the threshold limits specified in standards. However, this background distortion information is not used for calculating the real harmonic emission from the wind turbine leading to misleading voltage harmonics assessment from the wind turbine. In this paper a methodology for assessing the real harmonic emission from wind turbines is proposed based on current and voltage measurements where the background harmonic distortion at the Point of Common Coupling is considered.

Spin-Orbit Torques and Magnetization Switching in (Bi,Sb)2Te3/Fe3GeTe2 Heterostructures Grown by Molecular Beam Epitaxy.

Topological insulators (TIs) hold promise for manipulating the magnetization of a ferromagnet (FM) through the spin-orbit torque (SOT) mechanism. However, integrating TIs with conventional FMs often leads to significant device-to-device variations and a broad distribution of SOT magnitudes. In this work, we present a scalable approach to grow a full van der Waals FM/TI heterostructure by molecular beam epitaxy, combining the charge-compensated TI (Bi,Sb)2Te3 with 2D FM Fe3GeTe2 (FGT). Harmonic magnetotransport measurements reveal that the SOT efficiency exhibits a non-monotonic temperature dependence and experiences a substantial enhancement with a reduction of the FGT thickness to 2 monolayers. Our study further demonstrates that the magnetization of ultrathin FGT films can be switched with a current density of Jc ∼ 1010 A/m2, with minimal device-to-device variations compared to previous investigations involving traditional FMs.

Winding of geodesic rays chosen by a harmonic measure

Winding of geodesic rays chosen by a harmonic measure

Frequency Measurement Under Non-Sinusoidal Conditions.

Frequency measurement is an important issue in electrical engineering. Electric power systems have become increasing complex over the last decade. The use of distributed generation, the connection of non-linear loads and the presence of unexpected system faults are the main causes of frequency variations. In addition, power quality includes frequency as an important index. From a hardware instrumentation point of view, frequency measurement has different requirements: i.) Large power systems have slow frequency variation due to the high inertia of the overall network. This kind of problem requires frequency measuring methods capable of detecting small and also slow frequency variations. ii.) Small power systems can have frequency variation due to their reduced short-circuit power capacity. This type of problem requires fast methods with the capacity to detect large frequency variations. There are different groups of methods intended for frequency measurement. The methods can be compared in terms of computation and dynamic response, especially when the main voltage is disturbed. This research work focuses on frequency measurement under non-sinusoidal conditions. The paper studies the behaviour of a modified version of Sezi’s method and its hardware implementation using a microcontroller. This system can be used for frequency measurement or as a synchronized sampling source in harmonic measurement (e.g. EN 61000-4-7) The fast time response of the system enables it to be used in almost all kinds of application: small and slow frequency variations; frequency triggering in power system protection and power quality index characterisation.

Harmonic response of Gd-doped Mn-ferrite nanoparticles under AC magnetic field and optimization of Gd doping for MPI applications

This study synthesized Gd-doped Mn-ferrite nanoparticles for magnetic particle imaging (MPI) applications with doping levels (x) of 0, 0.05, 0.07, and 0.10. Analyses using X-ray diffraction measurements unequivocally confirmed the presence of a spinel-type crystal structure in the synthesized particles and X-ray absorption fine-structure spectroscopy confirmed the incorporation of Gd atoms in place of Mn within the crystal lattice. Magnetization and harmonic measurements under an AC magnetic field revealed that particles with a high initial permeability and low coercivity showed a high response intensity. Notably, particles possessing a Gd doping level of x = 0.07 displayed the highest response and were considered promising as MPI materials.

Quantifying the impact of varying inductive burden when inductive current transformers are used for harmonic current measurements for Grid Code compliance

Quantifying the impact of varying inductive burden when inductive current transformers are used for harmonic current measurements for Grid Code compliance

Self-correction for resolver second harmonic angle measurement error

Self-correction for resolver second harmonic angle measurement error

High-pressure synthesis of acentric sodium pyrocarbonate, Na2[C2O5

The inorganic pyrocarbonate salt Na2[C2O5] crystallizes in the acentric, monoclinic space group P21 with Z = 2. It contains monovalent alkali metal cations together with isolated pyrocarbonate anions. The [C2O5]2--groups consist of two planar [CO3]2--groups which are slightly tilted with respect to each other around the bridging oxygen atom. Na2[C2O5] was synthesized in a laser-heated diamond anvil cell at 20(2) GPa by heating a mixture of Na2[CO3] + CO2 to ≈800(200) K. Its crystal structure was obtained by single crystal synchrotron X-ray diffraction and confirmed by density functional theory-based calculations in combination with Raman spectroscopy. Second harmonic generation measurements verified the acentric space group symmetry. The crystal structure is characterized by alternating layers of Na+-cations and [C2O5]2--complex anions.

A New Method to Represent the Harmonic Measurement Accuracy of Current Transformers

A New Method to Represent the Harmonic Measurement Accuracy of Current Transformers

Continuous Harmonic Analysis and Power Quality Measurements in Three-Phase Systems.

A virtual instrument, named Power Quality Meter, is presented for (a) measuring power consumption and harmonics in three-phase systems, under non-sinusoidal and imbalance conditions (b) detecting, classifying and organizes power disturbance events. Measurement of the power consumption follows the formulation proposed by the members of the IEEE Working Group on Nonsinusoidal Situations (1996). So, definitions are based on the analysis of functions in the frequency domain, separating the fundamental terms from the harmonic terms of the Fourier series. The virtual instrument has been developed too for monitoring and measuring power disturbances, which are automatically classified and organized in a database while they are being recorded. Software tools use the database structure to present summaries of power disturbances and locate an event by severity or time of occurrence. Records of actual measurements are included to demonstrate the versatility of the instrument.

Multi-harmonic sources identification and evaluation method based on cloud-edge-end collaboration

With the increase of power electronic devices such as distributed renewable energies, energy storage, and flexible loads, the disturbance sources are rapidly raised and distributed in multiple voltage levels in the distributed network. The harmonics they produce are random and uncertain, and the massive amounts of data propose high demands on server computing capability, which restrict harmonic sources evaluation and significantly influence the judgments of the power quality in the distribution network. In order to improve the power quality and the harmonic source evaluation function of the distribution network, in this paper, a framework for multi-harmonic source identification and evaluation based on cloud-edge-end collaboration is proposed. Firstly, based on the analysis of the functional requirements harmonic sources evaluation in multiple voltage levels, a novel framework of cloud-edge-end collaboration is proposed. Secondly, the cloud-edge-end collaborative harmonic sources evaluation method which executes different service strategies according to voltage levels and grid operation based on the multi-level interaction of edge computing is proposed. Further, the working principle of the proposed novel framework with multiple evaluation methods including the dominant harmonic source identification, concentrated multiple harmonic sources evaluation (CMHSE) and hierarchical harmonic sources evaluation (HHSE) is described in detail in order to show the completed work processes of the proposed framework. Finally, the performance of the proposed method is verified based on the real data measured from different realistic urban power grids in China. The proposed method can effectively evaluate harmonic contributions in distribution systems and in turn provide a basis for harmonic mitigation measures.

Determination of Reservoir Oxidation Zone Formation in Uranium Wells Using Ensemble Machine Learning Methods

Approximately 50% of the world’s uranium is mined in a closed way using underground well leaching. In the process of uranium mining at formation-infiltration deposits, an important role is played by the correct identification of the formation of reservoir oxidation zones (ROZs), within which the uranium content is extremely low and which affect the determination of ore reserves and subsequent mining processes. The currently used methodology for identifying ROZs requires the use of highly skilled labor and resource-intensive studies using neutron fission logging; therefore, it is not always performed. At the same time, the available electrical logging measurements data collected in the process of geophysical well surveys and exploration well data can be effectively used to identify ROZs using machine learning models. This study presents a solution to the problem of detecting ROZs in uranium deposits using ensemble machine learning methods. This method provides an index of weighted harmonic measure (f1_weighted) in the range from 0.72 to 0.93 (XGB classifier), and sufficient stability at different ratios of objects in the input dataset. The obtained results demonstrate the potential for practical use of this method for detecting ROZs in formation-infiltration uranium deposits using ensemble machine learning.

Room-Temperature van der Waals Ferromagnet Switching by Spin-Orbit Torques.

The emerging wide varieties of the van der Waals (vdW) magnets with atomically thin and smooth interfaces hold great promise for next-generation spintronic devices. However, due to the lower Curie temperature of the vdW ferromagnets than room temperature, electrically manipulating its magnetization at room temperature has not been realized. In this work, it is demonstrated that the perpendicular magnetization of the vdW ferromagnet Fe3 GaTe2 can be effectively switched at room temperature in the Fe3 GaTe2 /Pt bilayer by spin-orbit torques (SOTs) with a relatively low current density of 1.3 × 107 A cm-2 . Moreover, the high SOT efficiency of ξDL ≈ 0.28 is quantitatively determined by harmonic measurements, which is higher than those in Pt-based heavy metal/conventional ferromagnet devices. The findings of room-temperature vdW ferromagnet switching by SOTs provide a significant basis for the development of vdW-ferromagnet-based spintronic applications.

Harnack inequality and one-endedness of UST on reversible random graphs.

We prove that for recurrent, reversible graphs, the following conditions are equivalent: (a) existence and uniqueness of the potential kernel, (b) existence and uniqueness of harmonic measure from infinity, (c) a new anchored Harnack inequality, and (d) one-endedness of the wired uniform spanning tree. In particular this gives a proof of the anchored (and in fact also elliptic) Harnack inequality on the UIPT. This also complements and strengthens some results of Benjamini et al.(Ann Probab 29(1):1-65, 2001). Furthermore, we make progress towards a conjecture of Aldous and Lyons by proving that these conditions are fulfilled for strictly subdiffusive recurrent unimodular graphs. Finally, we discuss the behaviour of the random walk conditioned to never return to the origin, which is well defined as a consequence of our results.