New selective earth faults only current directional method for isolated neutral systems

In order to achieve total selectivity at electrical distribution networks it is of great importance to analyze the defect currents at ungrounded power systems. This information will help to grant selectivity at electrical distribution networks ensuring that only the defect line or feeder is removed from service. In the present work a new selective and directional protection method for ungrounded power systems is evaluated. The new method measures only defect currents to detect earth faults and works with a directional criterion to determine the line under faulty conditions. The main contribution of this new technique is that it can detect earth faults in outgoing lines at any type of substation avoiding the possible mismatch of traditional directional earth fault relays. This detection technique is based on the comparison of the direction of a reference current to the direction of all earth fault capacitive currents at all the feeders connected to the same bus bars. This new method has been validated through computer simulations. The results for the different cases studied are remarkable, proving total validity and usefulness of the new method

Consideration of Multi-Phase Criterion in the Differential Protection Algorithm for High-Impedance Grounded Synchronous Generators

The generator differential protection is one of the most important electrical protections of synchronous generator stator windings. Its operation principle is based on the comparison of the input current and output current at each phase winding. Unwanted trip commands are usually caused by CT saturation, wrong CT selection, or the fact that they may come from different manufacturers. In generators grounded through high impedance, only phase-to-phase or three-phase faults can be detected by the differential protection. This kind of fault causes differential current to flow in, at least, two phases of the winding. Several cases of unwanted trip commands caused by the appearance of differential current in only one phase of the generator have been reported. In this paper multi-phase criterion is proposed for generator differential protection algorithm when applied to high impedance grounded generators

Review of Loss of Excitation Protection Setting and Coordination to the Generator Capacity Curve

After the liberalization of electricity market the absorption of reactive power by some generator is subsidized in order to support the power system voltage regulation. The setting of the loss of excitation protection is essential to warranties the correct operation of the generator in the under-excited area. A conservative setting does not allow the maximum reactive power absorption. On the other hand a setting which allows the maximum reactive power absorption could be dangerous. This paper presents a review of different settings recommendations for the loss of excitation protection and theirs coordination to the synchronous machine capacity curve. The settings have been validated through computer simulations

Acciones de acogida del proyecto mentor de la EUITI

Desde el curso académico 2008/2009 el Proyecto Mentor de la Escuela Universitaria de Ingeniería Técnica Industrial (EUITI) de la UPM [1] participa en distintas acciones de acogida de los alumnos de nuevo ingreso propio del centro. Estas actividades son el primer contacto de los mentores con los alumnos de nuevo ingreso y además son reforzadas por el apoyo y experiencia de los tutores y mentores del curso anterior, favoreciendo la interrelación de alumnos de distintos cursos y especialidades. Para la correcta realización de estas actividades, los alumnos mentores reciben un intensivo programa de formación que incluye aspectos psicosociales propios de la mentoría [2]. La presente comunicación tiene el propósito de describir dichas acciones así como presentar y valorar los resultados obtenidos a través de la encuest

La Hora TutHora: una herramienta de ordenación académica para incrementar la acción tutorial en la Escuela Universitaria de Ingeniería Técnica Industrial de la UPM

La reciente puesta en marcha de las titulaciones adaptadas al RD 1393/2007 constituía la oportunidad largamente esperada de implementar una serie de proyectos ilusionantes asociados a la Declaración de Bolonia y a su “nebulosa”. Entre ellos, la mejora del rendimiento en la Acción Tutorial constituye, para la UPM, uno de los aspectos prioritarios. En ese ámbito, la E.U. de Ingeniería Técnica Industrial ha desarrollado, desde el curso 2010/2011, un proyecto denominado “La Hora TutHora”, cuyo objetivo consiste en actuar desde Ordenación Académica para favorecer la mencionada Acción Tutorial. Este artículo expone los resultados que han podido medirse tras un año de vida del proyecto

La Acción Tutorial incentivada durante los dos últimos cursos académicos con el proyecto de "La Hora Tuthora"

La puesta en marcha de las titulaciones adaptadas al RD 1393/2007 constituía la oportunidad largamente esperada de implementar una serie de proyectos ilusionantes asociados a la Declaración de Bolonia y a su “nebulosa”. Entre ellos, la mejora del rendimiento en la Acción Tutorial constituye, para la UPM, uno de los aspectos prioritarios. En ese ámbito, la E.U. de Ingeniería Técnica Industrial ha desarrollado, desde el curso 2010/2011, un proyecto denominado “La Hora TutHora”, cuyo objetivo consiste en actuar desde Ordenación Académica para favorecer la mencionada Acción Tutorial. Este artículo expone los resultados que han podido medirse tras dos años de vida del proyecto, las conclusiones que pueden obtenerse y el planteamiento de propuestas de mejora

New methods and protection systems for AC and DC power networks

This thesis focuses on the study and development of new protection methods and systems for power cables used in both AC and DC grids, from generation to distribution or transmission power networks. In AC networks there are many protection functions that allow clearing ground faults from the measurements of currents and voltages obtained from the measurement devices as current transformers, voltage transformers or both. In some applications at transition stations from overhead lines to underground lines, the up and running protection relays can detect the ground fault and develop a correct tripping of the circuit breakers associated to such overhead or underground line. Those protection relays don´t know actually if the ground fault has happened at the overhead side or at the underground side. This circumstance is extremely important in order to allow having auto-reclosing attempts or not. If the order to switch on again the circuit breakers and restore power supply is developed under active ground fault conditions, the consequences can be dramatic if the permanent ground fault is at the underground line side. If the isolation and dielectric characteristics of the underground cables were already relatively damaged, a direct attempt to switch on the circuit breakers will cause a permanent damage in such cables forever and they will have to be replaced by new ones with the consequent lose of power supply for long time. This work proposes new protection methods that identifies if the ground fault has happened at the overhead line side or at the underground cable side. It can release the autoreclosing attempts to minimize the power oscillations of the grid as much as possible when the ground fault has happened at the overhead line side, or block them when the ground fault happened at the underground cable side. So far, no protection relays manufacturers have developed any relay with these characteristics, just the commonly named as SOTF (Switch On To Fault) which is described in the state of the art. During the development of this thesis, some patents which are property of the Universidad Politécnica de Madrid have been obtained for both AC applications. One of them (P201431962: Method to Determine a Ground Fault Emplacement in Circuits with Transitions Overhead Line to Underground Cable Line) has been recently licensed (dated on 23-January-2017) to DSF Tecnologías para Motores y sus Aplicaciones, S.L.with contract nº NL170020064, as they are the Spanish Distributor of the German company Woodward-Seg which designs, develops and manufactures protection relays for low, medium and high AC voltage networks for the last forty years, and showed high interest in including the concepts of this patent in a new protection relay. One of the challenges of this work was to develop new cable protection methods that could be implemented in protection relays in the easiest possible way and, at the same time, with the lowest possible investments. All new methods request the application of current and voltage transformers or sensors actually in use worldwide. In DC grids there are not so many protection functions in operation because high voltage DC networks are not used widely. Nevertheless, power transmission lines also have protection systems to clear ground faults. Normally, DC power links are one-to-one and the main protections are included in the AC/DC converter at the DC side. Multiterminal grids are not installed in a great deal so no big experience is known when facing up the challenge of erecting these kinds of new DC grids. Thinking in new multiterminal grids in DC, more protections functions must be developed in order to grant full selectivity in such grids. New protection concepts for DC cable power networks have been evaluated, simulated and tested with good results for ground faults at the positive or negative cables. In the same way that happened with the research for AC networks, during the development of this thesis, other patents which are property of the Universidad Politécnica de Madrid were obtained for DC power cable protection. The most important task of this work was to develop new protection methods that could be implemented in protection relays in the easiest possible way and, at the same time, with the lowest possible investments. All new methods request the application of standard current sensors actually in use worldwide. This document starts with the description of the actual protection functions used for detecting and clearing ground faults at AC and DC power networks. It follows a complete description of the new detecting methods that includes their operating principles. The simulation tool used for signal analysis of currents and voltages is also described including simulation and laboratory test results. At the end of this document, the main conclusions and improvements in cable ground fault detection for AC and DC networks developed in this work are written. Future research lines are also described and included

Diagnosis of Insulation Condition of MV Switchgears by Application of Different Partial Discharge Measuring Methods and Sensors

Partial discharges (PD) measurement provides valuable information for the condition assessment of the insulation status of high-voltage (HV) electrical installations. During the last three decades, several PD sensors and measuring techniques have been developed to perform accurate diagnostics when PD measurements are carried out on-site and on-line. For utilities, the most attractive characteristics of on-line measurements are that once the sensors are installed in the grid, the electrical service is uninterrupted and that electrical systems are tested in real operating conditions. In medium-voltage (MV) and HV installations, one of the critical points where an insulation defect can occur is inside metal-clad switchgears (including the cable terminals connected to them). Thus, this kind of equipment is increasingly being monitored to carry out proper maintenance based on their condition. This paper presents a study concerning the application of different electromagnetic measuring techniques (compliant with IEC 62478 and IEC 60270 standards), together with the use of suitable sensors, which enable the evaluation of the insulation condition mainly in MV switchgears. The main scope is to give a general overview about appropriate types of electromagnetic measuring methods and sensors to be applied, while considering the level of detail and accuracy in the diagnosis and the particular fail-save requirements of the electrical installations where the switchgears are located

Kuenftige Entwicklungsmoeglichkeiten des Europaeischen Fernstudienzentrums Sachsen-Anhalt Auf der Grundlage einer Bestandsaufnahme zur wissenschaftlichen Weiterbildung und zu Fernstudienangeboten in Sachsen-Anhalt

'In their 'Report about the Evaluation of the Distance Study Centre of the State of Saxony-Anhaltine at the Fachhochschule Anhalt' (EFZSA) on 11/12 January 2001, the group of external evaluators issued an altogether positive statement and recommended to provide the Distance Study Centre with a long-term guarantee to continue its work. However, they also voiced the opinion that there were still a number of open questions concerning the future perspectives of the EFZSA. This has caused the Centre to commission a short-term expertise to the Institute of Higher Education Research in Wittenberg asking for the development of different scenarios for the future of the EFZSA and an assessment of their potential for realisation. HoF Wittenberg carried out an empirical stock taking of all public and private continuing education activities currently existing in the tertiary sector in Saxony-Anhaltine as well as all projects in the field of multimedia and distance studies currently an offer or in the process of being organised. Due to the considerable heterogeneity of this educational sector the complete and comprehensive stock taking originally envisaged could only be approximated. As a result five scenarios have been developed for the possible future direction of EFZSA reaching from a pessimist zero scenario an the one hand to a highly dynamic development scenario an the other. The implementation of the individual scenarios is dependant an adequate framework conditions which are discussed in particular in the development scenario.' (author's abstract)'In ihrem 'Bericht ueber die Evaluierung des Fernstudienzentrums des Landes Sachsen-Anhalt (EFZSA) an der Fachhochschule Anhalt' am 11./12. Januar 2001 haben die Evaluatoren eine fuer das EFZSA insgesamt positive Stellungnahme abgegeben und empfohlen, das Fernstudienzentrurn langfristig zu garantieren. Hinsichtlich der kuenftigen Entwicklungsmoeglichkeiten des EFZSA sind nach ihrer Meinung jedoch noch eine Reihe von Fragen offen, die das EFZSA veranlasst haben, das Institut fuer Hochschulforschung Wittenberg zu beauftragen, kurzfristig eine Expertise abzugeben und verschiedene Szenarien fuer die moegliche Weiterentwicklung des EFZSA zu erarbeiten und deren Realisierungsbedingungen abzuschaetzen. Hierfuer wurde eine empirische Bestandsaufnahme der zur Zeit in Sachsen-Anhalt bestehenden oeffentlichen und privaten Weiterbildungsaktivitaeten im tertiaeren Bereich sowie der in Sachsen-Anhalt existierenden oder im Aufbau begriffenen Projekte multimedialer Fernlehre erarbeitet. Es wurde so weit wie moeglich Vollstaendigkeit angestrebt. Angesichts der grossen Heterogenitaet dieses Bildungssektors konnte die angestrebte Vollstaendigkeit sicherlich nur naeherungsweise erreicht werden. Im Ergebnis wurden fuenf Szenarien fuer die moegliche Entwicklung des EFZSA erarbeitet, die von einem pessimistischen Null-Szenario auf der einen bis hin zu einem zupackenden Entwicklungs-Szenario auf der anderen Seite reichen. Die Realisierung der einzelnen Szenarien ist an entsprechende Rahmenbedingungen gebunden, die vor allem im Entwicklungs-Szenario thematisiert werden.' (Autorenreferat)Available from UuStB Koeln(38)-20020106859 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Novel Auto-Reclosing Blocking Method for Combined Overhead-Cable Lines in Power Networks

This paper presents a novel auto-reclosing blocking method for combined overhead-cable lines in power distribution networks that are solidly or impedance grounded, with distribution transformers in a delta connection in their high-voltage sides. The main contribution of this new technique is that it can detect whether a ground fault has been produced at the overhead line side or at the cable line side, thus improving the performance of the auto-reclosing functionality. This localization technique is based on the measurements and analysis of the argument differences between the load currents in the active conductors of the cable and the currents in the shields at the cable end where the transformers in delta connection are installed, including a wavelet analysis. This technique has been verified through computer simulations and experimental laboratory tests