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A synchro-generator and a unijunction transistor oscillator in conjunction with a silicon-controlled rectifier form a detection and relay circuit for voltages appearing across the field of a three-phase alternator generated by negative-phase-sequence currents due to unbalanced conditions. Readings were taken of the times required for operation of the relay for various conditions of unbalance. Statistical studies were made to enable time predictions to be offered. It was concluded that the scheme offers the possibility of faster operation, and hence better protection and system stability, than is possible with existing types. In addition, the scheme will result in no loss of dependability over existing types, and the relay portion offers outstanding ruggedness and sensitivity. / M.S.

Uninterruptable Power Supply (UPS) systems have become essential to modern industries that require continuous power supply to manage critical operations. Since a failure of a single battery will affect the entire backup system, UPS systems providers must replace any battery before it runs dead. In this regard, automated monitoring tools are required to determine when a battery needs replacement. Nowadays, a primitive method for monitoring the battery backup system is being used for this task. This thesis presents a classification model that uses data mining cleansing and processing techniques to remove useless information from the data obtained from the sensors installed in the batteries in order to improve the quality of the data and determine at a given moment in time if a battery should be replaced or not. This prediction model will help UPS systems providers increase the efficiency of battery monitoring procedures. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

Nas subestações das grandes concessionárias de distribuição de energia elétrica coexistem sistemas de proteção com diferentes tecnologias, formados por relés eletromecânicos, estáticos e digitais, que, em alguns casos, continuarão funcionando por algumas décadas. Essa diversidade de tecnologias implica em sistemas com características de hardware e software diferentes, o que dificulta a implantação de funcionalidades locais e remotas que sejam interoperáveis. Dessa forma, torna-se interessante desenvolver um sistema baseado nas diferentes plataformas de proteção do mercado, com o objetivo de integrar as informações dos relés de proteção de diferentes tecnologias e que se comunicam através de protocolos distintos, criando uma base de dados homogênea. Para isso é necessário realizar uma coleta de dados provenientes dos vários relés de proteção e disponibilizar as informações do sistema de proteção para uma base de dados, através de uma interface de protocolos, onde essas informações possam ser tratadas de maneira uniforme e organizadas de forma estruturada, otimizando a funcionalidade local da instalação e podendo alimentar um sistema central de gestão. / In substations of large electric power distribution companies coexist protection systems with different technologies, comprised of electromechanical, static and digital relays that, in some cases, will continue to work for a few decades. This technology diversity implies in systems with different features of hardware and software, which hampers the implementation of local and remote functionalities that are interoperable. It would be interesting to develop a system based on integrated functional use of different protection platforms on the market, aiming to integrate the information of protective relays from different technologies that communicate with different protocols, creating a homogeneous database. It would be necessary a collection of data from the various protection relays that, through an interface protocols, provide information from the protection system for a database where information can be treated uniformly and organized in a structured manner, optimizing the local functionalities and feeding a central management system.

Nas subestações das grandes concessionárias de distribuição de energia elétrica coexistem sistemas de proteção com diferentes tecnologias, formados por relés eletromecânicos, estáticos e digitais, que, em alguns casos, continuarão funcionando por algumas décadas. Essa diversidade de tecnologias implica em sistemas com características de hardware e software diferentes, o que dificulta a implantação de funcionalidades locais e remotas que sejam interoperáveis. Dessa forma, torna-se interessante desenvolver um sistema baseado nas diferentes plataformas de proteção do mercado, com o objetivo de integrar as informações dos relés de proteção de diferentes tecnologias e que se comunicam através de protocolos distintos, criando uma base de dados homogênea. Para isso é necessário realizar uma coleta de dados provenientes dos vários relés de proteção e disponibilizar as informações do sistema de proteção para uma base de dados, através de uma interface de protocolos, onde essas informações possam ser tratadas de maneira uniforme e organizadas de forma estruturada, otimizando a funcionalidade local da instalação e podendo alimentar um sistema central de gestão. / In substations of large electric power distribution companies coexist protection systems with different technologies, comprised of electromechanical, static and digital relays that, in some cases, will continue to work for a few decades. This technology diversity implies in systems with different features of hardware and software, which hampers the implementation of local and remote functionalities that are interoperable. It would be interesting to develop a system based on integrated functional use of different protection platforms on the market, aiming to integrate the information of protective relays from different technologies that communicate with different protocols, creating a homogeneous database. It would be necessary a collection of data from the various protection relays that, through an interface protocols, provide information from the protection system for a database where information can be treated uniformly and organized in a structured manner, optimizing the local functionalities and feeding a central management system.

Protective relays are important parts of the power system. The protection guards valuable equipment, and protective relays play a vital role in performing the task. The relay detects fault conditions within an assigned area, opens and closes output contacts to cause the operation of other devices under its control. The relay acts to operate the appropriate circuit breakers to prevent damage to personnel and property. To ensure consistent reliability and proper operation, protective relay equipment must be evaluated and tested. The importance of the relay evaluation issue is linked to capability to test the relays and relaying systems using very accurate waveform representation of a fault event. The purpose of testing protective relays is to ensure correct operation of the relay for all possible power system conditions and disturbances. To fulfill this purpose, relay testing in varying network configurations and with different fault types is required. There are a variety of options that have different performance potentials and implementation constraints. Use of digital simulators to test protective relays has proven to be an invaluable mean to evaluate relay performance under realistic conditions. This thesis describes a new methodology that attempts to improve the existing practices in testing relays by using advanced digital simulator hardware, different software packages for network modeling, and new software tools for generating and replaying test waveforms. Various types of microprocessor relays are tested and evaluated through the set of scenarios. New methodology that combines different software packages to facilitate particular testing objectives is applied.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.Eng.)--Memorial University of Newfoundland, 1999. / Bibliography: leaves 140-143.

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.