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Thesis (Ph. D.)--Ohio University, August, 1981. / Title from PDF t.p.

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The contents of this thesis describe the results of an investigation into the means by which computer aided design (CAD) may be applied to the protection systems of electrical drives, removing much of the repetitive procedures presently used in determining relay settings. To further this aim, a series of algorithms have been devised which allow exploitation of the concept. The areas chosen for demonstration are, direct-on-line started induction motors and transformer fed variable speed drives. In both cases "standard settings' cannot be implemented as the field of application varies enormously. The text discusses an algorithm which utilises several databases containing motor, fuse and cable parameters. Chapter three uses a program derived from this algorithm which allows data to be extracted from the databases and manipulated in order to determine the optimum circuit components. Subsequent chapters examine the implementation of two types of motor protection relay and discusses the algorithms used in modelling them. The text is supported by applications which demonstrate the effectiveness of the derived programs. Chapter six discusses in depth the application of overcurrent relays for the protection of transformers used on variable speed drive installations. The possibility of using overcurrent elements in two or three phases is examined together with the attendant difficulties which may arise. The algorithms are further expanded to incorporate applications which involve the protection of multi-transformer installations supplied from a common point.

Relays in communication networks is a well-researched topic. Historically, relays were used in analog radio and television to extend the coverage. Using relays in wireless data networking applications is a more recent problem. In the early 2000s, relays were introduced for Micro-cellular and Wi-Fi deployments. Recently it has been considered for sensor networks and Vehicular Ad-hoc Networks (VANETs) applications. In this dissertation we present a novel approach to determine the optimal bounds for the Medium Access Control (MAC) throughput at the target receiver in a multi-hop multi-rate wireless data network. For a given relationship between the throughput and the distance, and a given distance between the access point and the target receiver, there is a minimum number of nodes that provides the maximum throughput to the target receiver. It is always desirable to optimize the deployment from various aspects. These aspects are application-dependent and they range from energy conservation in sensor networks to throughput and coverage maximization in data networks. We apply this novel appoach to vehicular ad-hoc network (VANET) scenarios. Using multi-hop relays, we show how to determine the optimum throughput for communciation between two vehicles. The optimal number of relays is chosen to maximize the throughput for point-to-point communication between a source and a destination as well as broadcast among all vehicles in the coverage area of the source. Additionally, in the physical layer, performance issues arise from the effects of interference and fading. The physical layer performance will in turn impact medium access control performance, effectively reducing the network throughput. We evaluate the performance of dense small cells for wireless local area networks (WLAN) and femto cells for data applications under the effects of interference and fading. We assume the network is fully saturated. We use the throughput-distance relationship to take into consideration the effects of interference, fading as well as the medium access control overheads. Using this model, we show that under certain conditions, the medium access control throughput for WLANs can outperform that of femto cells.

Faculty of Engineering and the Built Environment; School of Electrical and Information Engineering; MSC Dissertation / In the recent past the Eskom network operated out-of-step at three occasions. Eskom questions whether the out-of-step relays responded as they should have. This is based on the fact that not all the out-of-step relays operated during these events. This dissertation shows that shunts can make the impedance locus behave nonclassically to the extent that the present practices Eskom uses for out-of-step relaying become inappropriate for application at certain busbars of the network. This is illustrated by showing that when the characteristic of the relay at Hydra, situated on the Mpumalanga side of Hydra, is set using the classical approach, the mentioned relay will not detect swings that have their electrical centre south of Hydra. A modified two generator model is used to show the effect shunts have. The phrase “improved two generator model” refers to this model. The improved two generator model is derived to represent the section of the Eskom network that links Mpumalanga to the Western Cape.

Numerical relays are the result of the application of microprocessor technology in relay industry. Numerical relays have the ability to communicate with its peers, are economical and are easy to operate, adjust and repair. Modeling of digital and numerical relays is important to adjust and settle protection equipment in electrical facilities and to train protection personnel. Designing of numerical relays is employed to produce new prototypes and protection algorithms. Computer models of numerical relays for the study of protection systems are greatly enhanced when working along with an electromagnetic transient program (emtp). A literature survey has revealed that previous modeling techniques presented a lack of automation in the generation of relay models, or show high complexity in linking the numerical relay models with the power system modeled in the emtp. <p> This thesis describes a new approach of modeling and designing of numerical relays. The proposed methodology employs a Visual C++-based program (PLSA) to obtain from the user the specifications of the relay to be designed, and to process this information to generate the FORTRAN code that represents the functional blocks of the relay. This generated code is incorporated in a PSCAD/EMTDC case using a resource called component, which facilitates the creation of user-custom models in PSCAD/EMTDC. Convenient electrical and logical signals are connected to the inputs and outputs of the PSCAD/EMTDC component. Further additions of digital relay models into the PSCAD/EMTDC case constitute the protection system model. The thesis describes a procedure for designing distance and differential relay models, but the methodology may be extended to design models of other relay elements. <p> A number of protection system studies were performed with the structure created with the proposed methodology. Adjustment of distance and differential relays were studied. Relay performance under CT saturation and the effects of the removal of anti-aliasing analog filter were investigated. Local and remote backup distance protection of transmission lines was simulated. The adjustment of differential protection of power transformer to overcome the effects of inrush current was performed. Power transformer differential protection responses to internal and external faults were considered. <p>Additionally, a set of tests were performed to investigate the consistency of the relay models generated with the proposed methodology. The results showed that the numerical relay models respond satisfactorily according with the expected results of the tests.

Numerical relays are the result of the application of microprocessor technology in relay industry. Numerical relays have the ability to communicate with its peers, are economical and are easy to operate, adjust and repair. Modeling of digital and numerical relays is important to adjust and settle protection equipment in electrical facilities and to train protection personnel. Designing of numerical relays is employed to produce new prototypes and protection algorithms. Computer models of numerical relays for the study of protection systems are greatly enhanced when working along with an electromagnetic transient program (emtp). A literature survey has revealed that previous modeling techniques presented a lack of automation in the generation of relay models, or show high complexity in linking the numerical relay models with the power system modeled in the emtp. <p> This thesis describes a new approach of modeling and designing of numerical relays. The proposed methodology employs a Visual C++-based program (PLSA) to obtain from the user the specifications of the relay to be designed, and to process this information to generate the FORTRAN code that represents the functional blocks of the relay. This generated code is incorporated in a PSCAD/EMTDC case using a resource called component, which facilitates the creation of user-custom models in PSCAD/EMTDC. Convenient electrical and logical signals are connected to the inputs and outputs of the PSCAD/EMTDC component. Further additions of digital relay models into the PSCAD/EMTDC case constitute the protection system model. The thesis describes a procedure for designing distance and differential relay models, but the methodology may be extended to design models of other relay elements. <p> A number of protection system studies were performed with the structure created with the proposed methodology. Adjustment of distance and differential relays were studied. Relay performance under CT saturation and the effects of the removal of anti-aliasing analog filter were investigated. Local and remote backup distance protection of transmission lines was simulated. The adjustment of differential protection of power transformer to overcome the effects of inrush current was performed. Power transformer differential protection responses to internal and external faults were considered. <p>Additionally, a set of tests were performed to investigate the consistency of the relay models generated with the proposed methodology. The results showed that the numerical relay models respond satisfactorily according with the expected results of the tests.