1,722,765 research outputs found
Estimation of Geomagnetically Induced Currents (GICS) in the Namibian transmission network
No full textIncludes bibliographical references.Geomagnetically Induced Currents (GICs) have become a matter of concern not only to networks located in high magnetic latitude regions but also in networks located in mid-latitude regions. GICs pose a threat of transmission equipment damage which could lead to short power interruptions and potentially long term blackouts. Improved modelling techniques are essential in predicting the GICs flowing in the network in order to enable power utilities to reduce the risk of damage to equipment and improve the reliability of their power supply. This dissertation, entitled ESTIMATION OF GEOMAGNETICALLY INDUCED CURRENTS (GICS) IN THE NAMIBIAN TRANSMISSION NETWORK, aims at improving GIC estimation by installing measurement equipment in order to compare measured GIC results with modelled results. The purpose of which is to validate the calculation technique. The Nodal Admittance technique was proposed for the study and was first validated using published data obtained using the a&b parameter method. For the measurement techniques, two methods were found namely direct measurements in the transformer neutral conductor and indirect measurements in the transmission lines. In this dissertation, the former was implemented due to its simplicity in usage
Tuneable graphite intercalates for hydrogen storage
Full text linkThe development of hydrogen as an energy transfer mechanism is of great
importance to alleviate environmental damage and economic destabilisation
caused by over-reliance on oil, as long as the hydrogen can be generated renewably. To be suitable for road transport applications, safe and compact
hydrogen storage systems need to be developed, the primary technological
motivation for this PhD project which investigates hydrogen absorbed into
graphite intercalation compounds (GICs), to gain a fundamental physical understanding of the sorption processes to improve such materials' capacity for
hydrogen storage. Literature searching has led to a principal investigation,
primarily using neutron scattering and thermogravimetry, of potassium and
calcium-GICs with hydrogen. Inelastic neutron scattering on hydrogenated
KC24 has shown hydrogen sorption in this system to be quantitatively different from its analogues RbC24 and CsC24. A consistent model of the H2 sites
and dynamics has been proposed. Time-resolved structural data on the hydriding phase transition in KC8Hx have been obtained. A calcium-ammonia
intercalate has shown most promise for hydrogen storage, with uptake of 3.2
wt.% H2 at 77 K and 2 bar, a signifcant amount of the 6 wt.% target set by
the US DoE. It is concluded that available internal volume and donor charge
in GICs are critical parameters for optimising hydrogen uptake
10,9,8,7,6,......1 = Bloc GICS
Full text linkBloc GICS; Comunitat d'experts; Edició de contingutsBlog GICS; Expert community; Editor contentsBlog GICS; Comunidad de expertos; Edición de contenidosEl GICS (Grup de Gestió de la Informació en Ciències de la Salut) es constitueix a l'any 2003 a
l'empara del COBDC. Els integrants son professionals de la informació a l'àrea de ciències de
la salut. Els seus objectius es basen en compartir experiències i aportar coneixement a altres
professionals de l'àmbit a nivell científic, docent i de gestió. En aquest marc d'actuació neix
el bloc del GICS com a canal de comunicació i participació
GO-term enrichments for GICs.
No full textDirected acyclic graph created by GOrilla using Graphviz, displaying the most significantly enriched GO-process annotations for the annotated genes near GICs.</p
Network properties of 24 GICS sector networks.
No full textNetwork properties of 24 GICS sector networks.</p
El Suport a la recerca
Full text linkPresentat dins la jornada "10 anys de Gestió de la Informació en Ciències de la Salut (GICS)", organitzada pel grup GICS, del Col·legi Oficial de Bibliotecaris-Documentalistes de Catalunya (COBDC), amb l'objectiu d'analitzar com havien canviat els usuaris i els professionals de les biblioteques especialitzades en ciències de la salut durant els darrers 10 anys
SPDAs and GICs: like money in the bank?
Full text linkWe argue that changes in the life insurance industry have created a nontrivial moral hazard. We document the industry's shift from sales of life insurance to sales of mainly rate-of-return oriented investments like single premium deferred annuities (SPDAs) and guaranteed investment contracts (GICs). We describe the system of explicit and implicit guarantees that state governments and the industry provide to SPDA and GIC investors. We argue that these guarantees create moral hazards that have contributed to insurance company failures and misallocation of resources. We summarize reformers' proposals to enhance both the explicit guarantees and the regulation of insurance companies and argue that maintaining the degree of regulatory tightness required for such proposals to succeed will be difficult. We suggest an alternative: eliminate guarantees of SPDAs, GICs, and similar products (and possibly promote full disclosure practices and earmarked investments like variable annuities).Insurance industry
Desenvolvimento de instrumentação para medição de Correntes Geomagneticamente Induzidas (GICs) e efeito dos cabos de guarda em simulações de GICs
No full textDissertação de Mestrado Integrado em Engenharia Física apresentada à Faculdade de Ciências e TecnologiaAs Correntes Geomagneticamente Induzidas (GICs) são o resultado de variações rápidas no campo geomagnético terrestre e da condutividade finita da Terra. Ao longo de estruturas condutoras aterradas, como as redes de transporte de energia elétrica, as GICs podem fluir e, para tempestades geomagnéticas intensas, podem ser uma ameaça ao regular fornecimento de energia. Por esta razão, o interesse na modelação das GICs tem vindo a crescer.O trabalho desta dissertação consiste em simular o efeito dos cabos de guarda em modelos de GICs e na montagem e instalação de um instrumento de medição de GICs numa subestação da rede elétrica. Os cabos de guarda podem transportar GICs tal como as linhas de transmissão de energia. Um circuito equivalente simples que considera o efeito das resistências e das forças eletromotrizes induzidas (fem) ao longo dos cabos de guarda foi concebido. Este modelo é uma extensão de um modelo já estudado que considerava apenas as resistências dos cabos de guarda. Foram realizados testes usando parâmetros teóricos e também parâmetros reais de duas linhas de transmissão da rede elétrica nacional. Os resultados mostram que, para alguns casos, é importante considerar os cabos de guarda e, se for utilizado o circuito equivalente, a fem induzida deve ser considerada. Além disso, ao aumentar a complexidade do modelo de circuito adicionando mais linhas de transmissão de energia a uma subestação, o circuito equivalente apresentado nesta dissertação tem uma precisão maior do que o circuito equivalente que despreza a fem induzida. Para validar os valores previstos nos modelos, é importante fazer medições de GICs. Esta dissertação também abrange a tarefa de construir e instalar um sistema de medição para monitorização de GICs no neutro de um determinado transformador. O sistema consiste num sensor de corrente de efeito Hall e foi construído sobre uma Raspberry Pi 4 com um conversor analógico-digital de alta resolução (24 bits). Os testes preliminares em laboratório mostram uma precisão de medição de 0.056A. O sistema foi instalado na Subestação de Paraimo da REN e está operacional a recolher dados já tendo registado alguns eventos candidatos a GICs para além da expectável modulação diurna devida às variações de temperatura.Geomagnetically Induced Currents (GICs) are the result of rapid variations in the Earth's geomagnetic field and of the finite Earth's conductivity. Along grounded conducting structures such as transmission power networks, GICs can flow and, for extreme events, can be a threat to the power system normal operation. For this reason, interest in modeling GICs has been growing. This thesis work consists both in simulating the shield wire effects on GICs models and in assembling and installing a GIC measuring instrument at a power grid substation. Shield wires can carry GICs similarly to power transmission lines. A simple equivalent circuit model that considered the effect of resistances and induced electromotive forces (emf) along the shield wires was derived. This model is an extension of an already studied model that consider only shield wire resistances. Tests were done using synthetic parameters and also realistic parameters from two Portuguese transmission lines. Results show that for some cases, it is important to consider shield wires and if the equivalent circuit is used, the induced emf must be taken into consideration. In addition, when increasing the complexity of the circuit model by connecting more power transmission lines to a substation, the equivalent circuit presented in this thesis has a higher accuracy than the equivalent circuit that neglects the induced emf. GIC measurements should be taken in order to validate predicted values from GIC models. This thesis also encompasses the task of assembling and installing a measuring system to monitor GICs in the neutral of a given transformer. The system relies on a Hall effect current sensor and it was built over a Raspberry Pi 4 with a high resolution digitizer (24-bits). Preliminary tests in laboratory show a measurement precision of 0.056A. The system was installed at Paraimo Substation from REN and it is operational to collect data having already registered some candidate events for GICs in addition to the expected diurnal modulation due to temperature variations.FC
Prediction of geomagnetically induced currents (GICs) flowing in Japanese power grid for Carrington-class magnetic storms
Full text linkAbstract Large-amplitude geomagnetically induced currents (GICs) are the natural consequences of the solar–terrestrial connection triggered by solar eruptions. The threat of severe damage of power grids due to the GICs is a major concern, in particular, at high latitudes, but is not well understood as for low-latitude power grids. The purpose of this study is to evaluate the lower limit of the GICs that could flow in the Japanese power grid against a Carrington-class severe magnetic storm. On the basis of the geomagnetic disturbances (GMDs) observed at Colaba, India, during the Carrington event in 1859, we calculated the geoelectric disturbances (GEDs) by a convolution theory, and calculated GICs flowing through transformers at 3 substations in the Japanese extra-high-voltage (500-kV) power grid by a linear combination of the GEDs. The estimated GEDs could reach ~ 2.5 V/km at Kakioka, and the GICs could reach, at least, 89 ± 30 A near the storm maximum. These values are several times larger than those estimated for the 13–14 March 1989 storm (in which power blackout occurred in Canada), and the 29–31 October 2003 storm (in which power blackout occurred in Sweden). The GICs estimated here are the lower limits, and there is a probability of stronger GICs at other substations. The method introduced here will be immediately applicable for benchmark evaluation of low-latitude GICs against the Carrington-class magnetic storms if one assumes electrical parameters, such as resistance of transmission lines, with sufficient accuracy
Measurements of GICs in Austria in Sept 2017
No full textThe files contain measurements of geomagnetically induced currents (GICs) flowing through the neutral points of two transformers in separate substations in the Austrian power grid. The data cover a period of days in September 2017 when there was one of the strongest geomagnetic storms in the recent years, and subsequently some of the largest GICs recorded in Austria thus far. These are used as an example demonstrating the effectiveness of a GIC forecasting method based on neural networks.gic_1and5_meas_sept2017.csv - the measurements from substations #1 and #5.gic_1_pred_sept2017.csv and gic_5_pred_sept2017.csv - predictions of GICs from incoming solar wind data using a neural network.More information on the measurements and how they were carried out can be found in https://doi.org/10.1029/2021SW002912 . This data is used in the work described in https://doi.org/10.1002/essoar.10508699.1 .</div
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