Impact of DC Transient Disturbances on Harmonic Performance of Voltage Transformers for AC Railway Applications

This paper analyzes the impact of typical DC transient events occurring in railway grids on the frequency performance of instrument transformers (ITs) installed onboard trains and in AC substations for power quality (PQ) applications. PQ monitoring in railway systems is an issue of great interest because it plays a key role in the improvement of energy efficiency. The measurement chain for the PQ measurements, at 15 kV at 16.7 Hz and 25 kV at 50/60 Hz, commonly includes ITs to scale the voltage to levels fitting the input of the measurement units. Nevertheless, the behavior of ITs in the presence of PQ phenomena represents an open issue from a normative point of view, even for those installed in conventional AC power supply systems. In this context, the paper presents a possible definition of DC transient disturbances test waveforms, a measurement procedure, and a setup to assess the impact of these disturbances on the harmonic performances of ITs for railway systems. Preliminary experimental tests carried out on two commercial ITs under wide ranges of variation for the amplitude and the time duration of DC disturbances show that, in some cases, the error introduced in harmonic measurements can exceed 100%

A simplified procedure for the accurate frequency response identification of voltage transformers

The paper proposes a simplified and affordable procedure for instrument transformers frequency characterization for medium voltage applications. It consists of a two steps measurement procedure, where both steps involve the generation of sine waves only, so that the it can be easily performed in instrument transformers calibration laboratories without requiring additional generation features. In the first step, a 50 Hz measurement of the Voltage Instrument Transformer ratio error at rated voltage is performed. The second step consists of a frequency sweep performed at low voltage up to the first resonance. By these two data sets, an approximated but accurate frequency response can be easily obtained using a non-linear fitted model. In the paper, a commercial voltage instrument transformer for medium voltage grids is characterized by the proposed method; results are shown and validated by comparison with a reference frequency characterization performed at INRIM under rated voltage. © IMEKO TC-4 2020

Intra-Articular Hybrid Hyaluronic Acid Injection Treatment in Overweight Patients with Knee Osteoarthritis: A Single-Center, Open-Label, Prospective Study

Abstract: Background: A BMI > 25 is the most decisive, albeit modifiable, risk factor for knee osteoarthritis (KOA). This study aimed at assessing the efficacy of intra-articular injections of hybrid hyaluronic acid (HA) complexes (Sinovial® H-L) for the treatment of KOA in overweight patients in terms of disease severity, cardiocirculatory capacity, and quality of life. Materials: In this single-site, open-label, prospective trial, 37 patients with symptomatic knee OA were assessed at baseline and 3 months after ultrasound-guided intra-articular injection of hybrid HA complexes (Sinovial® H-L). Results: Primary variables displaying a statistically significant improvement after treatment were pain (VAS), disease severity (WOMAC), and cardiopulmonary capacity (6 min walk test). Among secondary variables, quality of life (SF-12) improved significantly, as did analgesic intake for pain control. No statistically significant difference was observed in body fat and muscle mass percentage measured by bioelectrical impedance analysis. Conclusions: Intra-articular hybrid HA injections are significantly effective in improving OA-related disease severity, cardiopulmonary function, and analgesic intake. This supports the role of hybrid HA viscosupplementation as a nonpharmacological treatment to relieve pain, reduce disability, improve quality of life, and limit the risk of polypharmacy in overweight patients with knee OA

Novel Calibration systems for the dynamic and steady-state testing of digital instrument transformers

Within the frame of the European project 'Future Grid II-Metrology for the next-generation digital substation instrumentation', several partners developed traceable calibration systems which allow the calibration of conventional or non-conventional instrument transformers (IT) even with a sampled value (digital) output according to IEC 61869-9. Different setups are prepared to allow the calibration with complex test waveforms to emulate steady state, dynamic or temporary events during the assessment of the ITs. The laboratory calibration setups for either current transformers or voltage transformers are briefly described. Several results obtained for different kind of voltage or current transformers are presented

Calibration of Current Transformers in distorted conditions

In the context of modern power systems, where there are lots of non-linear loads and generators based on switching power electronics, the accurate measurement of voltage and current harmonics is a key task for the knowledge of the actual state of the network. Voltage and current transducers play a crucial role since they are always the first part of the measurement chain. Currently, classical voltage and current instrument transformers are the most installed transducers, but their performance not always is fully characterized in the presence of distorted waveforms. Therefore, in this paper a calibration setup for the accurate characterization of current transformers with distorted waveforms is presented. System implementation and characterization is presented; then it is employed for the evaluation of the performance of a commercial current transformer in distorted conditions

Calibration of Current Transformers in distorted conditions

In the context of modern power systems, where there are lots of non-linear loads and generators based on switching power electronics, the accurate measurement of voltage and current harmonics is a key task for the knowledge of the actual state of the network. Voltage and current transducers play a crucial role since they are always the first part of the measurement chain. Currently, classical voltage and current instrument transformers are the most installed transducers, but their performance not always is fully characterized in the presence of distorted waveforms. Therefore, in this paper a calibration setup for the accurate characterization of current transformers with distorted waveforms is presented. System implementation and characterization is presented; then it is employed for the evaluation of the performance of a commercial current transformer in distorted conditions

The Low- and Intermediate-Mass Stellar Population in the Small Magellanic Cloud: The Central Stars of Planetary Nebulae

We present a study on the central stars (CSs) of Planetary Nebulae (PNe) observed in the Small Magellanic Cloud (SMC) with the Space Telescope Imaging Spectrograph instrument on-board the HST. The stellar magnitudes have been measured using broad-band photometry, and Zanstra analysis of the nebulae provided the stellar temperatures. From the location of the CSs on the HR diagram, and by comparing the observed CSs with current models of stellar evolution, we infer the CSs masses. We examine closely the possibility of light contamination in the bandpass from an unrecognized stellar companion, and we establish strong constraints on the existence and nature of any binary companion. We find an average mass of 0.63 Msun, which is similar to the mass obtained for a sample of CSs in the LMC (0.65 Msun). However, the SMC and LMC CS mass distributions differ slightly, the SMC sample lacking an intermediate-mass stellar population (0.65 to 0.75 Msun). We discuss the significance and possible reasons for the difference between the two mass distributions. In particular, we consider the differences in the star formation history between the clouds and the mass-loss rate dependence on metallicity.Comment: 30 pages, 6 figures, 5 tables. To be published in ApJ (October 20

Planetary Nebula Abundances and Morphology: Probing the Chemical Evolution of the Milky Way

This paper presents a homogeneous study of abundances in a sample of 79 northern galactic planetary nebulae whose morphological classes have been uniformly determined. Ionic abundances and plasma diagnostics were derived from selected optical line strengths in the literature, and elemental abundances were estimated with the Ionization Correction Factor developed by Kingsbourgh & Barlow (1994). We compare the elemental abundances to the final yields obtained from stellar evolution models of low-and intermediate-mass stars, and we confirm that most Bipolar planetary nebulae have high nitrogen and helium abundance, and are the likely progeny of stars with main-sequence mass larger than 3 solar masses. We derive =0.27, and discuss the implication of such a high ratio in connection with the solar neon abundance. We determine the galactic gradients of oxygen and neon, and found Delta log (O/H)/Delta R=-0.01 dex/kpc$ and Delta log (Ne/H)/Delta R=-0.01 dex/kpc. These flat PN gradients do not reconcile with galactic metallicity gradients flattening with time.Comment: The Astrophysical Journal, in pres

Clinical, pathological and microbiological profiles of spontaneous enteropathies in growing rabbits

[EN] In a rabbit production facility, health monitoring for enteropathies was performed in 15 production cycles for 20 mo. For each cycle, up to a hundred 35 d old rabbits weaned the same day were randomly selected, reared in the same fattening unit, but separately from the source batch and fed with the same feed except for antimicrobial supplementation. Clinical symptoms and enteric lesions of the selected group were recorded, using two checklists with binomial response (yes/no answer to a list of 54 clinical and enteric variables). The day after weaning, one week later, at the beginning of the enteric symptoms and 4-5 d after the start of the symptoms, inocula from the small intestine and caecum of selected animals were subjected to microbiological, C. spiroforme, Eimeria oocyst and rotavirus antigen detection tests. Representative samples of E. coli and C. perfringens isolates were tested, respectively, for serotype, biotype, eae, afr/2 genes and for a, b1, b2, e, i and enterotoxin toxin genes. The answers to the clinical-pathological variables were subjected to statistical analysis with a cluster analysis programme in order to obtain homogeneous, statistically significant groups of diseased animals (clusters). Then, the clusters were statistically associated with the laboratory outcomes. The cluster to which the enterotyphlitis lesions significantly contributed was associated with E. coli detection, E. coli O103 serotype detection and C. spiroforme ("several elements" variable). C. spiroforme ("rare elements" variable) was significantly associated with a cluster, characterised by a pathological profile consisting of bloating/rumbling noise and liquid content in stomach and caecum, without enteric inflammation. C. perfringens was significantly associated with a cluster, characterised by a pathological profile consisting of dilation/liquid content of small intestine, caecal impaction and mucoid content in the colon. Eighteen out of twenty-fi ve C. perfringens strains, examined for their toxin genotypes, proved to be toxin type A, while 7 out of 25 strains showed the a and b2 toxin genes in combination. The rotavirus antigen and Eimeria oocysts were detected from healthy rabbits (specimens of the day after weaning and one week later) in about 15% of specimens examined, but their presence in the sick animals was not significantly associated with any cluster.This study was supported by a financial contribution from Avitalia, Unione Nazionale Associazioni di Produttori Avicunicoli, Forlì, Italy, as part of the programme entitled “Miglioramento della qualità, della gestione dell’offerta delle produzioni cunicole e di rafforzamento dei rapporti di filiera. Azione 4.3”. Our thanks go to breeder Leta Covelli and Dasco srl for supplying the rabbits, to our colleague Romolo Salini and to Fabrizio Agnoletti of the Istituto Zooprofilattico Sperimentale del Veneto, Trevise, ItalyBadagliacca, P.; Letizia, A.; Candeloro, L.; Di Provvido, A.; Di Gennaro, A.; Scattolini, S.; Pompei, G.... (2010). Clinical, pathological and microbiological profiles of spontaneous enteropathies in growing rabbits. World Rabbit Science. 18(4):187-198. doi:10.4995/wrs.2010.77518719818