Accurate Assessment of Decoupled OLTC Transformers to Optimize the Operation of Low-Voltage Networks

Voltage control in active distribution networks must adapt to the unbalanced nature of most of these systems, and this requirement becomes even more apparent at low voltage levels. The use of transformers with on-load tap changers is gaining popularity, and those that allow different tap positions for each of the three phases of the transformer are the most promising. This work tackles the exact approach to the voltage optimization problem of active low-voltage networks when transformers with on-load tap changers are available. A very rigorous approach to the electrical model of all the involved components is used, and common approaches proposed in the literature are avoided. The main aim of the paper is twofold: to demonstrate the importance of being very rigorous in the electrical modeling of all the components to operate in a secure and effective way and to show the greater effectiveness of the decoupled on-load tap changer over the usual on-load tap changer in the voltage regulation problem. A low-voltage benchmark network under different load and distributed generation scenarios is tested with the proposed exact optimal solution to demonstrate its feasibility.Ministerio de Economía y Competitividad ENE2014-54115-RMinisterio de Economía y Competitividad ENE2017-84813-RUnión Europea (FEDER Interconecta) CDTI PASTORAITC- 2018110

The Merit-Order Effect of Energy Efficiency

The integration of certain amount of renewable generation in the wholesale market right-shifted the merit-order generation curve, which produces a noticeable reduction of the clearing price while slightly increases the traded energy (almost inelastic demand curve). The downward pressure on the clearing price is mainly due to the fact that the introduction of renewable generation bids with very low (even null) marginal cost, displaces to the right all kinds of conventional technologies (with higher marginal cost), including the technology which would otherwise have set the clearing market price. This right-shifted displacement of the merit-order generation curve leads to a lower wholesale clearing price, a small increment of the traded energy and a reduction of the total cost of the traded energy in the wholesale market. This is the key mechanism and its main effects on the market of the very well-known meritorder effect of the renewables. The promotion of energy-efficiency plans (industry and domestic) by policy-makers is expected to yield a reduction of the demand. As a result of the reduction of demand bids, the merit-order demand curve would experience a left-sifted displacement, which would produce a reduction of both the clearing price and the amount of traded energy. Consequently, the total cost of the traded energy also would diminish. As can be seen, the parallelism of the main effects on the market between the integration of renewable and energy efficiency evidences the existence of what can be called the merit-order effect of energy efficiency. To analyze the characteristics of this merit-order effect of the energy efficiency, a simplified model, based on the linearization of the market around the clearing point, is developed. This simplified model is also used to compare the merit-order effect of energy efficiency and renewables. A set of scenarios with energy efficiency and renewables have been generated in order to quantify the main effects on the Spanish/Iberian market for the year 2014

Renewables versus efficiency. A comparison for Spain

Along the last decades, renewable energy (especially wind) in Spain has undergone a significant development (lead by a small group of renewable promoters supported by institutional policies), contributing significantly to electric generation mix (42.8% renewable in 2014). On the contrary, the promotion of energy efficiency actions (accomplished by a large number of industrial and domestic consumers that are very poorly supported by energy policies), are still little explored. According to ODYSSEE-MURE, energy efficiency at the EU-28 level improved by 1.2%/year on average from 2000 to 2013, while for the case of Spain, the rate of improvement was only 0.6 %/year on average throughout that period (the lowest rate of energy efficiency improvement in the EU-28). This work seeks to compare the integration of renewable production with energy efficiency plans, in order to advance their potential economic impact in the wholesale market and consumers. To reach that goal, the hourly market data retrieved from the Spanish/Iberian Market Operator (OMIE) for 2014 will be used as a base. Then, a set of pseudoheuristic scenarios with integration of renewable production and energy efficiency (load saving) will be elaborated and analyzed to quantify what are expected to be the main effects on the Spanish electricity market and consumers. The results will show that energy efficiency exhibits the best performance in terms of economic efficiency (less cost of the traded energy) and environmental sustainability (greater replacement of fossil fuels).Ministerio de Economía y Competitividad PCIN-2015-043Ministerio de Economía y Competitividad ENE2015-69597-RMinisterio de Economía y Competitividad ENE2014-54115-

Actuaciones correctoras para el control de tensiones en redes de distribución y de los flujos de potencia reactiva en los transformadores transporte/distribución

El objetivo del trabajo que se presenta en este artículo consiste en el desarrollo de técnicas para la determinación de actuaciones sobre ciertas variables de control, a disposición de los gestores de redes de distribución, para mantener las tensiones de los nudos en la red mallada de distribución y los flujos de potencia reactiva por los transformadores transporte/distribución dentro de los límites establecidos, manteniendo al mismo tiempo un adecuado margen de actuación en las variables de contro

The Traspena meteorite: heliocentric orbit, atmospheric trajectory, strewn field, and petrography of a new L5 ordinary chondrite

The Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76∘.7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s−1. Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4∘.55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. Fortunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm−3This paper was supported by the Xunta de Galicia (Spain) under the ED431B 2020/38 grantS

Reversions of QuantiFERON-TB Gold Plus in tuberculosis contact investigation: A prospective multicentre cohort study

Background: Interferon-y Release Assays (IGRA) reversions have been reported in different clinical scenarios for the diagnosis of tuberculosis (TB) infection. This study aimed to determine the rate of QuantiFERON-TB Gold Plus (QFT-Plus) reversions during contact investigation as a potential strategy to reduce the number of preventive treatments. Methods: Prospective, multicentre cohort study of immunocompetent adult contacts of patients with pulmonary TB tested with QFT-Plus. Contacts with an initial positive QFT-Plus (QFT-i) underwent a second test within 4 weeks (QFT-1), and if negative, underwent a repeat test 4 weeks later (QFT-2). Based on the QFT-2 result, we classified cases as sustained reversion if they remained negative and as temporary reversion if they turned positive. Results: We included 415 contacts, of whom 96 (23.1%) had an initial positive test (QFT-i). Following this, 10 had negative QFT-1 results and 4 (4.2%) of these persisted with a negative result in the QFT-2 (sustained reversions). All four sustained reversions occurred in contacts with IFN-γ concentrations between ≥0.35 and ≤0.99 IU•mL-1 in one or both QFT-i tubes. Conclusion: In this study, TB contact investigations rarely reveal QFT-Plus reversion. These results do not support retesting cases with an initial positive result to reduce the number of preventive treatments

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Introducción del autoaprendizaje mediante la elaboración de las memorias de laboratorio

Se describe un trabajo de innovación educativa orientado a alumnos de primeros cursos de enseñanzas técnicas (Teoría de Circuitos), basada en la introducción de las técnicas de autoaprendizaje en el trabajo de laboratorio mediante la elaboración de memorias con formato libre, para mejorar el proceso de enseñanza de los alumnos. La actividad propuesta se ha diseñado para potenciar la adquisición de competencias tanto técnicas como transversales, y está orientada a la convergencia hacia Espacio Europeo de Educación Superior (EEES).Universidad de Sevilla. Instituto de Ciencias de la Educación (ICE): programa de formación de profesores novele