Estimation of zero-sequence impedance of undergrounds cables for single-phase fault location in distribution systems with electric arc

This paper focus on the problem of locating single-phase faults in mixed distribution electric systems, with overhead lines and underground cables, using voltage and current measurements at the sending-end and sequence model of the network. Since calculating series impedance for underground cables is not as simple as in the case of overhead lines, the paper proposes a methodology to obtain an estimation of zero-sequence impedance of underground cables starting from previous single-faults occurred in the system, in which an electric arc occurred at the fault location. For this reason, the signal is previously pretreated to eliminate its peaks voltage and the analysis can be done working with a signal as close as a sinus wave as possible

A comparative analysis of two methods for the calculation of electric-field-induced perturbations to molecular vibration

Two common methods of accounting for electric-field-induced perturbations to molecular vibration are analyzed and compared. The first method is based on a perturbation-theoretic treatment and the second on a finite-field treatment. The relationship between the two, which is not immediately apparent, is made by developing an algebraic formalism for the latter. Some of the higher-order terms in this development are documented here for the first time. As well as considering vibrational dipole polarizabilities and hyperpolarizabilities, we also make mention of the vibrational Stark effec

A quantum molecular similarity analysis of changes in molecular electron density caused by basis set flotation and electric field application

Quantum molecular similarity (QMS) techniques are used to assess the response of the electron density of various small molecules to application of a static, uniform electric field. Likewise, QMS is used to analyze the changes in electron density generated by the process of floating a basis set. The results obtained show an interrelation between the floating process, the optimum geometry, and the presence of an external field. Cases involving the Le Chatelier principle are discussed, and an insight on the changes of bond critical point properties, self-similarity values and density differences is performed

Evaluación de la biomasa como recurso energético renovable en Cataluña

El objetivo principal es la evaluación de la biomasa como recurso energético renovable en Cataluña. Su alcance requiere el estudio de diversas temáticas, desarrolladas en los doce capítulos que componen el documento.El Capítulo 1 describe los objetivos de la tesis. El Capítulo 2 describe los motivos que justifican la valorización energética del recurso biomasa. El Capítulo 3 presenta la metodología general utilizada. El Capítulo 4 realiza un análisis multicriterio del aprovechamiento energético de biomasa forestal. El Capítulo 5 cuantifica la biomasa disponible para usos energéticos en Cataluña. Los Capítulos 6, 7, 8 y 9 analizan las tecnologías y la viabilidad de la producción de energía con colza y chopo. El Capítulo 10 caracteriza físico-químicamente la biomasa de colza como combustible complementario al actual uso del grano para biodiesel. El Capítulo 11 evalua el uso de cultivos para la producción de productos químicos. El Capítulo 12 resume las Conclusiones generales.